Reloading measurements

Benchguy · December 17, 2023, 04:38 PM

I’m just curious if I’m the only person reloading that consistently sees various numbers when measuring what is supposed to be consistent numbers? Today when seating bullets I seem to not be able to obtain the same number case after case. Measuring Ogive and cartridge OAL ( which I know isn’t going to be consistent), but it’s driving me batty! Is it my press, which is old, my dies, the pressure I’m putting on the handle of the press? I also see numbers vary when trimming. The consistency isn’t grand, and maybe I’m never going to achieve that but it’s rare that every measurement is exact. Am I just hoping or is it possible?

totaldla · December 17, 2023, 07:24 PM

Welcome to the real world!

Every process has a variance. The trick (imo) is to have a realistic expectation and an understanding of what IS and ISN'T important.

E.g. you shouldn't expect frame a wall to within 1/8" and even if you could it wouldn't positively impact a door or window.

Benchguy · December 17, 2023, 08:07 PM

Quote:

Originally Posted by totaldla

Welcome to the real world!

Every process has a variance. The trick (imo) is to have a realistic expectation and an understanding of what IS and ISN'T important.

E.g. you shouldn't expect frame a wall to within 1/8" and even if you could it wouldn't positively impact a door or window.

Good point. I just thought the tools would produce more precision. It’s small numbers so the variations I’m seeing aren’t much. Being so new to watching the micrometer during reloading I expected to see every move produce a repeatable number. I guess just like anything you do there’s places that can afford more leniency and learning those places is important. I’m just trying figure out how to recognize those places that can have a window to fall within by watching and comparing. Also trying not to be annoying asking questions. Thanks for not blasting me. ��

cdoc42 · December 17, 2023, 08:24 PM

I'm with you, Benchguy, and I've been doing this for 47 years. Most often I find a variation in OAL when measured from "ogive" to case base. Same bullets; same lot number. I'll use my 6.5 Creedmoor as an example; I have a few reasons that I suspect:

My OAL target with a 140gr Hornady SP is 2.245" base-to-ogive, in MY rifle. It is not unusual to see swings from 2.242 to 2.248, even though most are 2.245. Frustrating!!

1) I don't trim all my rifle cases unless they exceed the maximum length, so does a difference of 0.01" make a difference even though most cases fall in between those two acceptable extremes? Find out: trim all cases every time to the same size.

2) I don't keep a record of the number of times I've reloaded any cases; when the primer goes in too easily, or the neck splits, or the head fractures, I toss that case.
So the potential difference in neck thickness, internal volume, or variable primer pressure may play a role. Find out: always use new cases from the same manufacturer (and even they may vary).

3) A very common and fixable situation is primer seating variation. If I see a longer-than-expected round, I stand it up on the table. If it wobbles, the primer is not seated deeply enough. I gently prime the case again by putting more pressure on that round and that invariably solves the problem. That takes me to:

4) I don't routinely clean the primer pockets unless they are obviously totally black.
Find out: routinely clean the pockets every time.

5) If you buy inexpensive bullets, there may be a difference in bullet base-to-ogive size among those bullets. I found that with a purchase of Remington 130gr PSP that was a bargain sale. I could not get them the seat to the same size more often than usual. I think they were on sale because they were seconds. When I measured the base-to-ogive among a group of 100, there was such a wide variation that I stopped using the bullets. Bench rest target bullets are least likely to have a major variation; hunting rounds even from the major manufacturers might differ slightly. I don't have experience with cast bullets in rifles.

6) I don't use the same primers each time. I may use CCI, Winchester, Remington, and Federal, based on what is available at the time. But I have not really experimented with all loads being the same except for the primers to establish if that affects my accuracy or velocity.

7) Then there's just ME. If every one of my hand loads is exquisitely perfect, am I holding exactly the same sight picture between rounds? Is trigger pressure the same? Am I holding my breath and letting it out slowly, then firing at the end of expiration -each time? Is the rifle in the rest in the same position each time? Did the rest change position between shots due to recoil? Did someone fire a shot precisely before I let mine go off? How about temperature and atmospheric pressure differences between range visits?

8) Just thought of this as an addition: Do you use the same pressure on your caliper when you measure the finished cartridge? I need a lot of luck to do that.

If you hand load just for hunting, putting all of your shots in an 8-inch circle at any given distance should suffice for at least, deer. If you load for competition, that's a whole different world. If you are like me -and maybe most of us here on TFL - your hobby is looking for that "bug hole" or as close to it as you can get. On a good day.

jetinteriorguy · December 17, 2023, 09:07 PM

This isn’t just a rabbit hole you’re starting down, it’s a bottomless pit of despair.

**44 AMP** · December 17, 2023, 10:21 PM

Think about this for a moment, ...TOLERANCES...
\
Everything you are working with has a range of tolerances (+/-) and as long as its within that range, its considered "in spec"

Here's a question, you're seating bullets, and getting SLIGHTLY different measurements, and you're looking for a cause.

Did you measure the bullets (all of them, each one individually) and check for variances before seating them??

A few thousandths difference in length is not just common, tis normal. Some slight variation of the diameter at given points from the bullet base are possible.

Measuring to the "ogive" is a vague thing, and can be completely different with each different bullet and firearm.

The seating stem is made to certain size. It will contact every bullet at the point that bullet is too large to enter into the cavity of the stem. But that point can be a different point on each different bullet.

Even before you look at anything else, if you have vairations in the bullets (and, you will) you are going to have variations in the end results.

We pay more for "match" bullets, expecting (and normally getting) less variation between each individual bullet. LESS, not ZERO.

Benchguy · December 18, 2023, 01:40 AM

You’re all giving me great advice and explanations. I’ve not measured individual bullets but they would definitely be a culprit in ogive variance. I’ve noticed that some bullets force me to change settings on seating depth. I got to the shooting bench the other day and found out 5 rounds were too long to fit into my magazine. After making sure I could manually eject them, I decided to load them individually and see where they hit. Wasn’t a terrible size group but where other bullets stopped seating, these will need to keep going. They also create more compaction of powder. Which is another thread I’ll start.

Thanks again for your input!

**Unclenick** · December 18, 2023, 06:16 PM

Most manufacturers combine the output of several sets of tooling in their lots of bullets. Small differences in the forming dies result in small differences in ogive curvature, which means the seating die doesn't meet then at quite the same difference from the base or tip. Not that hollow point tips on match bullets are often uneven and can vary upwards of 15 thousandths or so pretty commonly. Same for brass. If you want identical cartridge dimensions, you wind up having to sort bullets and brass before assembly.

But all this begs the question, what is your objective? I switched over to the Sinclair comparator inserts for bullets because their stainless steel profile is cut to mimic a chamber throat and not to catch the bullet higher up, as the aluminum Hornady comparator inserts do. For accuracy, I want to get the same bullet jump every time. This means the place where the bullet ogive meets the chamber throat has to be the same distance from the headspace-determining surface each time. For a rimless bottleneck cartridge, this means the difference between the shoulder datum and the bullet ogive's throat contact area must be constant. The cartridge is forced forward by the firing pin at ignition, so the distance between that part of the ogive and the shoulder datum is what actually determines the distance the bullet jumps to the throat. It doesn't matter if the COL varies a little or if the head-to-shoulder distance varies some, as long as the shoulder-to-ogive distance stays the same.

I built my own instrument for measuring this years ago, but you can get the Redding Instant Indicator to make this comparison directly and read it out on a dial indicator. You can also make separate head-to-shoulder measurements and head-to-ogive measurements, take their difference, and select match rounds that have the same difference. Only the difference matters, not the absolute values of the individual measurements. So the difference can be a nonsensical-looking number, and that's fine as long as it is consistent between rounds.

Nathan · December 18, 2023, 07:21 PM

Whenever you measure something, you are measuring the actual dimension + tool error + tool user error + process variation.

The key to the error is that it should be 1/10th or less of your measurement. You need to spend time with your tools to figure out how to reduce your error through developing measurement skill.

Then, I try not to focus on any single measurement that is within an acceptable range, but I do measure it and apply statistical process control principles to my data. This helps sort out the meaningful data from errors.

Benchguy · December 18, 2023, 08:06 PM

To be honest, I’m loading for a 5.56 AR so my efforts here may be in vain. It’s a great learning experience and my son is joining me in the process. I have a 1-6x32 Vortex Strike Eagle on it and it’s gone sub MOA so it’s pushing me to keep prying. I have a bolt action 22-250 a 22 Hornet and my son just bought himself a 6.5 Creedmore gas gun that we will also be loading for in the future. All the lessons we’re learning and this experience is not all for loss. We’re buying equipment together and it’s satisfying to know this will be passed along to him. There’s a couple more tools that will help us but with what we have this far, you folks are allowing us to keep honing in on our goals. If I can get to 1/2” MOA I’ll be happy. It’s going to be a varmint gun and if the couple loads I’m working on come down a little I’ll be pretty tickled.

Nathan · December 18, 2023, 08:49 PM

If you can get 20 shots within 1/2 MOA from a gas gun, you will have my attention!

That said, instead of fooling around with 3 shot groups, develop to understand group size from the mean radius and std deviation viewpoint. That will tell you your hit probability better than any 3 shot group will.

Benchguy · December 18, 2023, 09:23 PM

I suppose I need to be realistic about what my rig is capable of. Being a new gun, less than 200 rounds, I hope it will get better.

Are you using a program to get your MR or measuring them yourself? The article I just read mentions the Analyzer tool… would be nice to have it done by AI.

I actually needed to look up mean Radius. I need to do a little more reading on the subject but will see if I can use my old targets to come up with the MR. I’ve been shooting 5 shot groups. The recipe I think is working best at the moment was tested with 3 different primers and there seemed to be a difference in performance. I’ve loaded up 15 more of the chosen components and I plan to run them through to see how they perform. These 15 are all 2nd firing brass and more control was recognized and used in preparation of the brass. Ladder testing of TAC and Varget are in the current process. TAC loads are a continuance of said chosen combo but Varget is still being ladder tested.

Nathan · December 20, 2023, 07:35 PM

Ballistic-X is your friend. They say that the advanced version will do multiple targets as one group.

**Unclenick** · December 20, 2023, 08:41 PM

Take a look at Geoffrey Kolbe's article on group statistics.. It uses group size (extreme spread), but mentions earlier a proof done showing that radial standard deviation is actually the most reliable comparative statistic to use. It also discusses how many groups are needed for what level of confidence you can have in your determinations.

There is other software like OnTarget TDS that will overlay multiple groups. It is a good way to accumulate more holes than you could distinguish from one another if you shot them all into the same piece of paper.

One thing to keep in mind is that the group centers (mean location) also vary, and have their own standard deviation that determines how much they can wander away from what the ultimate population mean will be. This is called the standard error and is equal to the standard deviation divided by the square root of the number of holes in the sample. I generally pick a sample size such that two standard errors are no bigger than my smallest sight adjustment increment so I know my zero based on that group has a 95% chance of being off by no more than one click. However, there are situations where that doesn't matter, such as having a hunting rifle that groups enough smaller than the required kill zone that the gun's accuracy isn't an issue in whether or not you make the shot.

jetinteriorguy · December 20, 2023, 08:49 PM

Quote:

Originally Posted by Benchguy

I suppose I need to be realistic about what my rig is capable of. Being a new gun, less than 200 rounds, I hope it will get better.

Are you using a program to get your MR or measuring them yourself? The article I just read mentions the Analyzer tool… would be nice to have it done by AI.

I actually needed to look up mean Radius. I need to do a little more reading on the subject but will see if I can use my old targets to come up with the MR. I’ve been shooting 5 shot groups. The recipe I think is working best at the moment was tested with 3 different primers and there seemed to be a difference in performance. I’ve loaded up 15 more of the chosen components and I plan to run them through to see how they perform. These 15 are all 2nd firing brass and more control was recognized and used in preparation of the brass. Ladder testing of TAC and Varget are in the current process. TAC loads are a continuance of said chosen combo but Varget is still being ladder tested.

Another really good powder to look at is H4895, IME it was a tossup with Varget and narrowly edged it out.

Benchguy · December 21, 2023, 07:45 AM

Interesting article, Unclenick. I’m not a strong mathematician so the formula looks more difficult that just deciding that the combination I’ve got right now gives me a high percentage of success when it comes to connecting with the vitals of a coyote out to 300yards.

I shot a 15 round group yesterday and without applying the numbers in shot placement to a formula, the MR will be near 1.25”. I wasn’t keeping track of individual shots it twice there were overlapping 3 shot groups. These groups were separated by 1”.

One interesting outcome in my bench time came when I wasn’t able to get my muzzle high enough to get on target. I had a bag malfunction that required me to pause and reset my muzzle height. The next two shots were 3” higher than the center of the other 13 shots. It would tell me that the TAC powder is definitely temperature sensitive.

Thanks for the responses and suggestions! This group interacts well and I appreciate being a part of it. My contributions will likely never be as informative as those of you providing these experienced answers but maybe me asking questions as a noob will help others as well.

I purchased the $7.99 Ballistics X app but haven’t seen that I can add groups to overlay them yet.

Thanks all!

GeauxTide · December 21, 2023, 10:03 AM

Quote:

This isn’t just a rabbit hole you’re starting down, it’s a bottomless pit of despair.

Amen! I haven't worried about it for more than 50 years of loading.

**Unclenick** · December 21, 2023, 01:49 PM

This is the software I mentioned, but I don't think there's a mobile app version. Only the more expensive TDS system lets you overlap targets. There is a fifteen-day free trial on it, though, so if you get some target photos lined up before you install, you can get a taste of what you are in for. The TDS system also has a database of printable targets that you can shoot and scan, and with these targets, the software can automatically locate the hole centers for you. For other targets, you place holes manually, as with the Ballisticx X app.

RC20 · December 21, 2023, 06:23 PM

Quote:

E.g. you shouldn't expect frame a wall to within 1/8" and even if you could it wouldn't positively impact a door or window.

Phew, we framed to 1/16th of an inch and variation did indeed cause problems. You could work around them but it was better not to.

Benchguy · December 21, 2023, 08:02 PM

Quote:

Originally Posted by Unclenick

This is the software I mentioned, but I don't think there's a mobile app version. Only the more expensive TDS system lets you overlap targets. There is a fifteen-day free trial on it, though, so if you get some target photos lined up before you install, you can get a taste of what you are in for. The TDS system also has a database of printable targets that you can shoot and scan, and with these targets, the software can automatically locate the hole centers for you. For other targets, you place holes manually, as with the Ballisticx X app.

I don’t have a home pc so will check this out when I get back to work.

Wag · December 22, 2023, 07:37 AM

You're moving from the world of simply loading ammo to the world of fine-tuning ammo.

When I was fine-tuning, I continually learned that there was just one more variable I needed to control. And when one problem was solved, another three would arise that made it clear that there was more to do.

And I enjoyed all of it!

Made some pretty hyper-accurate ammo, too.

I don't do that any more. The last several batches of ammo I made were just plinking ammo and while they're plenty good, they are not what you'd call perfect by any stretch of the imagination.

I will say, that the biggest factor I ever had to deal with was cleaning my equipment. When I was loading lead bullets, the lube would start to come off in my seating die and I couldn't get consistent COL to save my life.

--Wag--

Benchguy · December 22, 2023, 08:03 AM

Quote:

Originally Posted by Wag

You're moving from the world of simply loading ammo to the world of fine-tuning ammo.

When I was fine-tuning, I continually learned that there was just one more variable I needed to control. And when one problem was solved, another three would arise that made it clear that there was more to do.

And I enjoyed all of it!

Made some pretty hyper-accurate ammo, too.

I don't do that any more. The last several batches of ammo I made were just plinking ammo and while they're plenty good, they are not what you'd call perfect by any stretch of the imagination.

I will say, that the biggest factor I ever had to deal with was cleaning my equipment. When I was loading lead bullets, the lube would start to come off in my seating die and I couldn't get consistent COL to save my life.

--Wag--

Coincidentally, I have started to add a second tumbling to the brass to keep the lube out of my seating die. After reading other threads on ruining your die by running dirty brass through it I made the decision to keep it as clean as possible. I’m going to start another thread on annealing brass shortly. Having just gotten to this point, I have collected a decent amount of brass accumulated that has factory annealing but I believe I need to continue with the brass I’m firing.

old roper · December 22, 2023, 08:40 AM

Here is something to read.

https://bergerbullets.com/shoot-bett...coal-and-cbto/

MarkCO · December 22, 2023, 09:30 AM

Quote:

Originally Posted by jetinteriorguy

This isn’t just a rabbit hole you’re starting down, it’s a bottomless pit of despair.

It's not really that bad. What is difficult is what one person says matters, really might not (at all or for you) and that what another says does not matter might really matter a lot. I've been reloading for a bit as well, and I am over 1.1M rounds hand-loaded now. I load bulk pistol anf AR ammo different from my Revolvers, hunting loads and match grade loads. I chrono a LOT and 5 shot groups at a minimum.

Mitigation (I did not say elimination) of variables is a goal, and the brass, bullets and powders we get do have variation, as well as the chambers. Some cartridges need some things others don't. The Creedmoors and PRCs cases are less finicky than say 7mm Mag. Barrels need to settle (when new and deep cleaned) but most people (for acceptable precision) clean them too much. And, a great load in one rifle is almost always going to be at least a good load in another...it's not voodoo, but you do need to figure out what each system likes. Optics and the shooter are big parts of the equation. Cheap scopes, parallax, poor fundamentals etc. make folks question their ammo when that is not the problem.

Each case depends on what you want to do with the rifle, how accurate you want to be, how meticulous you are with the other aspects of load development, and how much you shoot.

With precision bottle-neck rifle cartridges, much of what is "still" in vogue and done has been, in the last 15 years or so been abandoned as "trivial" or actually detrimental by the folks at the front of the class.

What is phenomenally interesting is that the men from the Houston Warehouse really gave us some good info to launch the next gen of rifle cartridge loading and barrel development.

"Chasing the lands" used to be a thing, and it is not anymore (if you learn what is best and what is not). Also (and there is a HUGE industry built around it) spending 1000s of dollars on a Prometheus, neck turning, etc. don't matter much if you do the other things right.

Redding Competition Shell Holders, Satterlee 1.0 and Satterlee 2.0 are the tools that have moved me to a much better, and much more efficient space.

First, OAL should be started with the base (for flat based and at the start of the shank for boat tails) of the bullet at the neck-shoulder junction. Then we do the Satterlee 1.0 (10 shot ladder test). Take the middle fired case from the node and set up your dies, with the Redding Competition Shell holder, for 1 to 2 thousands shoulder bump. Then go to Satterlee 2.0 to fine tune the OAL.

IF you are real lucky, the magazine will be compatible and your bullet will be at least 50 thousandths off the lands and you will be done with SDs under 5, extended barrel life and no chasing the lands.

That might be a little much for hunting rounds, great for precision rifle rounds and a little light for benchrest.

Benchguy · December 22, 2023, 11:52 AM

I need to retire so I’ve got time to watch and read! �� Seriously, thank you for all the information, all of you. I don’t think the “rabbit hole” is far off, but it’s just a time sink. I’m having to google a bunch of things to follow advice so I can put the words to lessons. I honestly could be satisfied with the recipe I have but there’s always this idea that it can be better. You all know that. �� MarCO mentioned optics and with my current rifle I am running the 1-6x32 Vortex Strike Eagle. Moving up to better magnification would pull my shots closer, I am sure. But if I’m hunting in a timber, close range will be the norm and it’s what I want out of the rifle. Reloading for it is relatively cheap and the lessons are important. I also own a REM 700 in 22-250 that has the potential to be a more accurate rifle. These lessons will be used for it down the road, as well as helping my son work into the skill with his 6.5 Creedmore.

Cheers for now!

December 17, 2023, 04:38 PM	#1
Benchguy Member Join Date: December 14, 2023 Location: Central Iowa Posts: 42	Reloading measurements I’m just curious if I’m the only person reloading that consistently sees various numbers when measuring what is supposed to be consistent numbers? Today when seating bullets I seem to not be able to obtain the same number case after case. Measuring Ogive and cartridge OAL ( which I know isn’t going to be consistent), but it’s driving me batty! Is it my press, which is old, my dies, the pressure I’m putting on the handle of the press? I also see numbers vary when trimming. The consistency isn’t grand, and maybe I’m never going to achieve that but it’s rare that every measurement is exact. Am I just hoping or is it possible?

December 17, 2023, 07:24 PM	#2
totaldla Senior Member Join Date: August 10, 2009 Location: SW Idaho Posts: 1,332	Welcome to the real world! Every process has a variance. The trick (imo) is to have a realistic expectation and an understanding of what IS and ISN'T important. E.g. you shouldn't expect frame a wall to within 1/8" and even if you could it wouldn't positively impact a door or window. __________________ Lee Auto Bench Prime Castor Oil Case Lube

December 17, 2023, 08:24 PM	#4
cdoc42 Senior Member Join Date: March 13, 2005 Location: Pennsylvania Posts: 1,698	I'm with you, Benchguy, and I've been doing this for 47 years. Most often I find a variation in OAL when measured from "ogive" to case base. Same bullets; same lot number. I'll use my 6.5 Creedmoor as an example; I have a few reasons that I suspect: My OAL target with a 140gr Hornady SP is 2.245" base-to-ogive, in MY rifle. It is not unusual to see swings from 2.242 to 2.248, even though most are 2.245. Frustrating!! 1) I don't trim all my rifle cases unless they exceed the maximum length, so does a difference of 0.01" make a difference even though most cases fall in between those two acceptable extremes? Find out: trim all cases every time to the same size. 2) I don't keep a record of the number of times I've reloaded any cases; when the primer goes in too easily, or the neck splits, or the head fractures, I toss that case. So the potential difference in neck thickness, internal volume, or variable primer pressure may play a role. Find out: always use new cases from the same manufacturer (and even they may vary). 3) A very common and fixable situation is primer seating variation. If I see a longer-than-expected round, I stand it up on the table. If it wobbles, the primer is not seated deeply enough. I gently prime the case again by putting more pressure on that round and that invariably solves the problem. That takes me to: 4) I don't routinely clean the primer pockets unless they are obviously totally black. Find out: routinely clean the pockets every time. 5) If you buy inexpensive bullets, there may be a difference in bullet base-to-ogive size among those bullets. I found that with a purchase of Remington 130gr PSP that was a bargain sale. I could not get them the seat to the same size more often than usual. I think they were on sale because they were seconds. When I measured the base-to-ogive among a group of 100, there was such a wide variation that I stopped using the bullets. Bench rest target bullets are least likely to have a major variation; hunting rounds even from the major manufacturers might differ slightly. I don't have experience with cast bullets in rifles. 6) I don't use the same primers each time. I may use CCI, Winchester, Remington, and Federal, based on what is available at the time. But I have not really experimented with all loads being the same except for the primers to establish if that affects my accuracy or velocity. 7) Then there's just ME. If every one of my hand loads is exquisitely perfect, am I holding exactly the same sight picture between rounds? Is trigger pressure the same? Am I holding my breath and letting it out slowly, then firing at the end of expiration -each time? Is the rifle in the rest in the same position each time? Did the rest change position between shots due to recoil? Did someone fire a shot precisely before I let mine go off? How about temperature and atmospheric pressure differences between range visits? 8) Just thought of this as an addition: Do you use the same pressure on your caliper when you measure the finished cartridge? I need a lot of luck to do that. If you hand load just for hunting, putting all of your shots in an 8-inch circle at any given distance should suffice for at least, deer. If you load for competition, that's a whole different world. If you are like me -and maybe most of us here on TFL - your hobby is looking for that "bug hole" or as close to it as you can get. On a good day. Last edited by cdoc42; December 17, 2023 at 08:26 PM. Reason: aadding info

December 17, 2023, 10:21 PM	#6
44 AMP Staff Join Date: March 11, 2006 Location: Upper US Posts: 29,027	Think about this for a moment, ...TOLERANCES... \ Everything you are working with has a range of tolerances (+/-) and as long as its within that range, its considered "in spec" Here's a question, you're seating bullets, and getting SLIGHTLY different measurements, and you're looking for a cause. Did you measure the bullets (all of them, each one individually) and check for variances before seating them?? A few thousandths difference in length is not just common, tis normal. Some slight variation of the diameter at given points from the bullet base are possible. Measuring to the "ogive" is a vague thing, and can be completely different with each different bullet and firearm. The seating stem is made to certain size. It will contact every bullet at the point that bullet is too large to enter into the cavity of the stem. But that point can be a different point on each different bullet. Even before you look at anything else, if you have vairations in the bullets (and, you will) you are going to have variations in the end results. We pay more for "match" bullets, expecting (and normally getting) less variation between each individual bullet. LESS, not ZERO. __________________ All else being equal (and it almost never is) bigger bullets tend to work better.

December 18, 2023, 06:16 PM	#8
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,128	Most manufacturers combine the output of several sets of tooling in their lots of bullets. Small differences in the forming dies result in small differences in ogive curvature, which means the seating die doesn't meet then at quite the same difference from the base or tip. Not that hollow point tips on match bullets are often uneven and can vary upwards of 15 thousandths or so pretty commonly. Same for brass. If you want identical cartridge dimensions, you wind up having to sort bullets and brass before assembly. But all this begs the question, what is your objective? I switched over to the Sinclair comparator inserts for bullets because their stainless steel profile is cut to mimic a chamber throat and not to catch the bullet higher up, as the aluminum Hornady comparator inserts do. For accuracy, I want to get the same bullet jump every time. This means the place where the bullet ogive meets the chamber throat has to be the same distance from the headspace-determining surface each time. For a rimless bottleneck cartridge, this means the difference between the shoulder datum and the bullet ogive's throat contact area must be constant. The cartridge is forced forward by the firing pin at ignition, so the distance between that part of the ogive and the shoulder datum is what actually determines the distance the bullet jumps to the throat. It doesn't matter if the COL varies a little or if the head-to-shoulder distance varies some, as long as the shoulder-to-ogive distance stays the same. I built my own instrument for measuring this years ago, but you can get the Redding Instant Indicator to make this comparison directly and read it out on a dial indicator. You can also make separate head-to-shoulder measurements and head-to-ogive measurements, take their difference, and select match rounds that have the same difference. Only the difference matters, not the absolute values of the individual measurements. So the difference can be a nonsensical-looking number, and that's fine as long as it is consistent between rounds. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

December 17, 2023, 09:07 PM	#5
jetinteriorguy Senior Member Join Date: April 28, 2013 Posts: 3,226	This isn’t just a rabbit hole you’re starting down, it’s a bottomless pit of despair.

December 18, 2023, 01:40 AM	#7
Benchguy Member Join Date: December 14, 2023 Location: Central Iowa Posts: 42	You’re all giving me great advice and explanations. I’ve not measured individual bullets but they would definitely be a culprit in ogive variance. I’ve noticed that some bullets force me to change settings on seating depth. I got to the shooting bench the other day and found out 5 rounds were too long to fit into my magazine. After making sure I could manually eject them, I decided to load them individually and see where they hit. Wasn’t a terrible size group but where other bullets stopped seating, these will need to keep going. They also create more compaction of powder. Which is another thread I’ll start. Thanks again for your input!

December 18, 2023, 07:21 PM	#9
Nathan Senior Member Join Date: July 1, 2001 Posts: 6,365	Whenever you measure something, you are measuring the actual dimension + tool error + tool user error + process variation. The key to the error is that it should be 1/10th or less of your measurement. You need to spend time with your tools to figure out how to reduce your error through developing measurement skill. Then, I try not to focus on any single measurement that is within an acceptable range, but I do measure it and apply statistical process control principles to my data. This helps sort out the meaningful data from errors.

December 18, 2023, 08:06 PM	#10
Benchguy Member Join Date: December 14, 2023 Location: Central Iowa Posts: 42	To be honest, I’m loading for a 5.56 AR so my efforts here may be in vain. It’s a great learning experience and my son is joining me in the process. I have a 1-6x32 Vortex Strike Eagle on it and it’s gone sub MOA so it’s pushing me to keep prying. I have a bolt action 22-250 a 22 Hornet and my son just bought himself a 6.5 Creedmore gas gun that we will also be loading for in the future. All the lessons we’re learning and this experience is not all for loss. We’re buying equipment together and it’s satisfying to know this will be passed along to him. There’s a couple more tools that will help us but with what we have this far, you folks are allowing us to keep honing in on our goals. If I can get to 1/2” MOA I’ll be happy. It’s going to be a varmint gun and if the couple loads I’m working on come down a little I’ll be pretty tickled.

December 18, 2023, 08:49 PM	#11
Nathan Senior Member Join Date: July 1, 2001 Posts: 6,365	If you can get 20 shots within 1/2 MOA from a gas gun, you will have my attention! That said, instead of fooling around with 3 shot groups, develop to understand group size from the mean radius and std deviation viewpoint. That will tell you your hit probability better than any 3 shot group will.

December 18, 2023, 09:23 PM	#12
Benchguy Member Join Date: December 14, 2023 Location: Central Iowa Posts: 42	I suppose I need to be realistic about what my rig is capable of. Being a new gun, less than 200 rounds, I hope it will get better. Are you using a program to get your MR or measuring them yourself? The article I just read mentions the Analyzer tool… would be nice to have it done by AI. I actually needed to look up mean Radius. I need to do a little more reading on the subject but will see if I can use my old targets to come up with the MR. I’ve been shooting 5 shot groups. The recipe I think is working best at the moment was tested with 3 different primers and there seemed to be a difference in performance. I’ve loaded up 15 more of the chosen components and I plan to run them through to see how they perform. These 15 are all 2nd firing brass and more control was recognized and used in preparation of the brass. Ladder testing of TAC and Varget are in the current process. TAC loads are a continuance of said chosen combo but Varget is still being ladder tested.

December 20, 2023, 07:35 PM	#13
Nathan Senior Member Join Date: July 1, 2001 Posts: 6,365	Ballistic-X is your friend. They say that the advanced version will do multiple targets as one group.

December 20, 2023, 08:41 PM	#14
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,128	Take a look at Geoffrey Kolbe's article on group statistics.. It uses group size (extreme spread), but mentions earlier a proof done showing that radial standard deviation is actually the most reliable comparative statistic to use. It also discusses how many groups are needed for what level of confidence you can have in your determinations. There is other software like OnTarget TDS that will overlay multiple groups. It is a good way to accumulate more holes than you could distinguish from one another if you shot them all into the same piece of paper. One thing to keep in mind is that the group centers (mean location) also vary, and have their own standard deviation that determines how much they can wander away from what the ultimate population mean will be. This is called the standard error and is equal to the standard deviation divided by the square root of the number of holes in the sample. I generally pick a sample size such that two standard errors are no bigger than my smallest sight adjustment increment so I know my zero based on that group has a 95% chance of being off by no more than one click. However, there are situations where that doesn't matter, such as having a hunting rifle that groups enough smaller than the required kill zone that the gun's accuracy isn't an issue in whether or not you make the shot. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

December 21, 2023, 07:45 AM	#16
Benchguy Member Join Date: December 14, 2023 Location: Central Iowa Posts: 42	Interesting article, Unclenick. I’m not a strong mathematician so the formula looks more difficult that just deciding that the combination I’ve got right now gives me a high percentage of success when it comes to connecting with the vitals of a coyote out to 300yards. I shot a 15 round group yesterday and without applying the numbers in shot placement to a formula, the MR will be near 1.25”. I wasn’t keeping track of individual shots it twice there were overlapping 3 shot groups. These groups were separated by 1”. One interesting outcome in my bench time came when I wasn’t able to get my muzzle high enough to get on target. I had a bag malfunction that required me to pause and reset my muzzle height. The next two shots were 3” higher than the center of the other 13 shots. It would tell me that the TAC powder is definitely temperature sensitive. Thanks for the responses and suggestions! This group interacts well and I appreciate being a part of it. My contributions will likely never be as informative as those of you providing these experienced answers but maybe me asking questions as a noob will help others as well. I purchased the $7.99 Ballistics X app but haven’t seen that I can add groups to overlay them yet. Thanks all!

December 21, 2023, 01:49 PM	#18
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,128	This is the software I mentioned, but I don't think there's a mobile app version. Only the more expensive TDS system lets you overlap targets. There is a fifteen-day free trial on it, though, so if you get some target photos lined up before you install, you can get a taste of what you are in for. The TDS system also has a database of printable targets that you can shoot and scan, and with these targets, the software can automatically locate the hole centers for you. For other targets, you place holes manually, as with the Ballisticx X app. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

December 22, 2023, 07:37 AM	#21
Wag Senior Member Join Date: October 22, 2010 Location: Albuquerque, NM Posts: 989	You're moving from the world of simply loading ammo to the world of fine-tuning ammo. When I was fine-tuning, I continually learned that there was just one more variable I needed to control. And when one problem was solved, another three would arise that made it clear that there was more to do. And I enjoyed all of it! Made some pretty hyper-accurate ammo, too. I don't do that any more. The last several batches of ammo I made were just plinking ammo and while they're plenty good, they are not what you'd call perfect by any stretch of the imagination. I will say, that the biggest factor I ever had to deal with was cleaning my equipment. When I was loading lead bullets, the lube would start to come off in my seating die and I couldn't get consistent COL to save my life. --Wag-- __________________ "Great genius will always encounter fierce opposition from mediocre minds." --Albert Einstein.

December 22, 2023, 08:40 AM	#23
old roper Senior Member Join Date: June 11, 2007 Posts: 2,157	Here is something to read. https://bergerbullets.com/shoot-bett...coal-and-cbto/ __________________ Semper Fi Vietnam 1965 VFW Life member NRA Life Member

December 22, 2023, 11:52 AM	#25
Benchguy Member Join Date: December 14, 2023 Location: Central Iowa Posts: 42	I need to retire so I’ve got time to watch and read! �� Seriously, thank you for all the information, all of you. I don’t think the “rabbit hole” is far off, but it’s just a time sink. I’m having to google a bunch of things to follow advice so I can put the words to lessons. I honestly could be satisfied with the recipe I have but there’s always this idea that it can be better. You all know that. �� MarCO mentioned optics and with my current rifle I am running the 1-6x32 Vortex Strike Eagle. Moving up to better magnification would pull my shots closer, I am sure. But if I’m hunting in a timber, close range will be the norm and it’s what I want out of the rifle. Reloading for it is relatively cheap and the lessons are important. I also own a REM 700 in 22-250 that has the potential to be a more accurate rifle. These lessons will be used for it down the road, as well as helping my son work into the skill with his 6.5 Creedmore. Cheers for now!