Loading 223 with the components that I already have

[mrappe]

Originally Posted by 44 AMP

Inserting a primed case and dropping the locked back bolt on to it is an "upper end test" and causes the primer to be struck harder than usual. IF you're ok there, you're very likely to be ok when feeding loaded rounds from the magazine.

The weight of a loaded round, and the force required to strip it from the magazine and push it into the chamber will slow down the bolt (slightly) so the firing pin won't bounce off the primer quite as hard.

The test for this is to use actual live ammo (Or dummies) where it is safe to do so, and fire a round or a few, then eject an unfired round from the chamber and examine the mark on the primer.

That is exactly what I was thinking too.

[mrappe]

Originally Posted by FrankenMauser

1:7 twist is fast for 55 gr bullets. Don't expect peak performance.
You'd be better off getting some 69-77 gr projectiles.

I would't think about throwing a way 500 bullets and I don't have another .223 gun to use them in. Besides I have shot plenty of 55 grn commercial ammo it the gun and never had bad accuracy with them. They might not be good for long range accuracy but they have been fine for plinking at 80 yds or so. In the future I plan on getting some heavier projectiles when loading with 5.56 brass and higher pressures for longer ranges.

[Shadow9mm]

Originally Posted by mrappe

I would't think about throwing a way 500 bullets and I don't have another .223 gun to use them in. Besides I have shot plenty of 55 grn commercial ammo it the gun and never had bad accuracy with them. They might not be good for long range accuracy but they have been fine for plinking at 80 yds or so. In the future I plan on getting some heavier projectiles when loading with 5.56 brass and higher pressures for longer ranges.

Ok, first off, 55s in a 1:7 should be totally fine.

I hate long dissertations but I'm gonna have to do one here to explain why some people do not like shooting 55s in 1:7 guns.

Think about a bullet like a tire on your car. If that tire is out of balance it will wobble around and vibrate. The faster you go the faster the tire spins and the worse the wobble and vibration becomes.

55s generally have a higher muzzle velocity than 69-77s, thus 55s generally rotate faster than the 69-77s given the same barrel twist rate.

55s are generally more of a bulk quality bullet and have less quality control on over all weight and jacket thickness than 69-77s. So 55s are more likely to be poorly balanced.

so in short 55s have more velocity, and less consistent jackets/balance, Making them more prone to accuracy problems in a faster twist barrel like a 1:7 because of the higher rotation speed magnifying these problems.

Factory loaded 223 ammo with bulk FMJ, in my testing and experience, has also had poor velocity consistency, which just generally makes for an inaccurate load. I have found my hand loaded 55g FMJ to shoot much better than any factory loads I have bought.

There are other way to make 55g bulk shoot better. I have done weight sorting on mine before. Mind you I am not recommending you do this, its more than a little tedious. But I weighed each bullet out of a 1000rnd bag. I eliminated the bullets that were way out of tolerance. And I found an area between 55.5-55.6 were a little over 600 of them were. I separated those are my A grade bullets. the Rest, except for the extremes, went into my B grade box. removing the oddballs on the top and bottom removed a lot of fliers. shooting my A grade bullets my groups tended to be smaller and more consistent hitting steel plates at longer ranges. B grade gets used for closer range drills CQB type drills. I just got some bullets from Arm or Ally for the first time, kind of testing them out. Got some information and a graph in another thread here.https://thefiringline.com/forums/sho...d.php?t=618483

[totaldla]

The term "floating firing pin" really doesn't apply to the AR15. Why? Because the spec firing pin is not physically long enough to protrude from the bolt face until the bolt is locked in place. The mass of a spec firing pin is not enough to fire a primer at the velocity of the bolt locking ( which is much slower than the initial speed of the bolt carrier group).

High primer, too long firing pin, sticking firing pin, or maybe a scenario where the hammer followed the BCG - could possibly cause a "slam fire".

[Shadow9mm]

totaldla

That's depends on the primer in question.


Do you think it is a coincidence that when the military created its primer specification that it changed the anvil angle to reduce sensitivity?


Or that CCI recommends those primers for use in the AR, along with the 450, which has a thicker cup which also reduces sensitivity?

I would expect CCI knows their primers, feel free to call them and ask yourself like I did. Use the manufacturers product in ways the don't recommend at your own risk.

[totaldla]

Originally Posted by Shadow9mm

totaldla

That's depends on the primer in question.


Do you think it is a coincidence that when the military created its primer specification that it changed the anvil angle to reduce sensitivity?


Or that CCI recommends those primers for use in the AR, along with the 450, which has a thicker cup which also reduces sensitivity?

I would expect CCI knows their primers, feel free to call them and ask yourself like I did. Use the manufacturers product in ways the don't recommend at your own risk.

Military 5.56 is used in a number firearms other than the AR15/16. Manufacturers make changes for the M249, that aren't needed in the other weapons.

The indent doesn't vary - I've tested this with pistol primers.
Primer seating depth matters. Primer height matters too (I read of too tall SRP). The point is that the speed the bolt carrier moves doesn't effect the indent - give it a try.

But

So-called "slam fires" happen so rarely that it is clear that the design is very robust. A bazzillion guys use CCI400, Fed205, and other "sensitive" primers with their AR15s - they might "blow" primers but they don't report slam fires.

Understanding the AR15 bolt design is helpful.

[jetinteriorguy]

Originally Posted by totaldla

Military 5.56 is used in a number firearms other than the AR15/16. Manufacturers make changes for the M249, that aren't needed in the other weapons.

The indent doesn't vary - I've tested this with pistol primers.
Primer seating depth matters. Primer height matters too (I read of too tall SRP). The point is that the speed the bolt carrier moves doesn't effect the indent - give it a try.

But

So-called "slam fires" happen so rarely that it is clear that the design is very robust. A bazzillion guys use CCI400, Fed205, and other "sensitive" primers with their AR15s - they might "blow" primers but they don't report slam fires.

Understanding the AR15 bolt design is helpful.

When I first started loading for my first AR15 about 20 years ago I had no clue about what a floating firing pin was or what a slam fire was. I had been shooting it some and worked up a pretty good load so I went ahead and loaded up a couple thousand rounds with CCI 400 SRP’s. Then I heard about the dreaded slam fire and went into panic mode. I pulled all 2000 rounds and managed to get a great deal from a friend on 5000 Tula primers that were more suitable and reloaded them for my stash. Since then though I’ve also gone back to using CCI400’s after more research and have shot a few thousand with absolutely no incident. The primers do get slightly dinged but haven’t caused any slam fires, the Tula primers show the same ding as well.

[rc]

The only time I've seen a slam fire bad enough to send a double tap was with Remington small pocket 7.62x39 in an SKS. Those have a massive firing pin and no rebound spring so they rely on heavy primers to be safe. I doubt the AR firing pin is anywhere near as heavy so there is not that much chance of setting off a primer. Even Springfield Armory 9mm 1911 that uses the titanium firing pin can have the trigger pulled, the hammer fall and no boom boom sometimes with just a mark left on the primer when hard or small rifle primers are used in place of soft small pistol primers. Remington 7.5s and IZQ ammo both had unreliable primer strikes for me in my Springfield target. I've never had a problem with the heavier steel firing pin in my Kimber 9mm setting off any primers. So applying that to AR15s, I'd say a light mark on a primer is nothing to worry about. I've seen marks on primers of cycled shotgun rounds too. No boom boom, just an artifact of the firing pin bounce from shucking the shell home.

[tangolima]

My A2 clone with 1:7 twist actually likes light bullets better; 55gr, 40gr, or even lighter varmint bullets. I was concerned about bullet disintegration, but no problem at all.

Slam fire happens more often in some gun designs than the others. AR design is among the good ones. But still less sensitive primer, if available, adds extra assurance. I don't believe the high primer theory. High primer causes misfires, which is opposite to slam fire. You can't have it on both ends.

-TL

Sent from my SM-N960U using Tapatalk

[mrappe]

25 years ago I had a Norinco AK type rifle in 223 and I had 2 slam fires with it. I found out that I had not gotten all of the cosmoline out of the bolt and that there was enough gunk in it that the firing pin would stick in the protruded position. Afterwards, I never had a problem with it.

[georgehwbush]

Shadow9mm (Factory loaded 223 ammo with bulk FMJ, in my testing and experience, has also had poor velocity consistency, which just generally makes for an inaccurate load. I have found my hand loaded 55g FMJ to shoot much better than any factory loads I have bought.)

yes hand loads 55vmax in my m4 16" 1:7 produce consistent sub-MoA 7 shot groups... i agree that good components carefully constructed, have no issue with fast twist.

that being said. Velocity 3250 f/s - Twist rate 1:7.00 in. - Rotation 334285 rpm. < if that were larger diameter it might fling itself apart from sheer centrofuge.

[georgehwbush]

i'm just saying; there has to be a logical limit, you couldn't expect cast bullets pushed to 3500ft/s from a 1:5 twist to stay togather... there are limits to anything and that is what some people are thinking of when they don't like the fastest twist and lightest pills.... just saying.

[Shadow9mm]

Considering, out of the 22-250, hornady pushes the 50g vmax up to 4000fps, and the 55g to 3680. And they load their 55g v-max in 223 at a listed 3240fps. And that they rate the v-max for a muzzle velocity between 2000-4000fps to function properly. I suspect you would have to push it a fair bit faster to get failure.

You should look at the limitations of the bullet in question. And fmj are not prone to disintegration like some light, thin jacketed, varmint bullets.

[Unclenick]

For the gray mist to appear part way to the target, bullet cross-sectional mass at groove diameter and RPM are what matter. A 22-250 has a 14" twist standard, so a bullet launched at 3250 RPM from a 7" twist AR would have to be launched at 6500 fps from the 14" twist 22-250 to achieve matching RPM.

In a standard cup-and-core bullet, Harold Vaughn was able to induce core stripping at about 3150 RPM in a .270 Winchester running a light bullet, and that would be spinning up with about 22% more peak angular acceleration torque if the peak pressure ratios are 65kpsi to 55 kpsi. Core stripping is where the lead core of a bullet slips inside the jacket because the torque accelerating it gets too high for the friction bond between the two to hold together. This results in the bullet slowing spin as it exits, and the spin rates of the core and jacket come back together in proportion to the spin rates and mass ratios of the two parts. At that point, due to the speed bumps the rifling's indentation of the jacket produces, the core is also a bit loose inside the jacket, and the resulting wobble produces terrible accuracy and can get eccentric enough to disintegrate the bullet on the way to the target.

Per earlier discussion elements, CCI told me over the phone that their number 41 military spec primer is just their 450 magnum primer with a shortened anvil to further reduce sensitivity. So, just using a 450 does not get you all the way down to military sensitivity specs. There are different ways to bring sensitivity down. CCI uses the short anvil. Federal uses a thicker primer cup rather than a different anvil in their GM205MAR military sensitivity spec small rifle primer, according to an email reply I got from them when I wrote to ask them about it. I don't know what Winchester is doing in their number 41. The military ones may do one of those things or may use a less sensitive priming compound. I don't know how they are getting there. I have a drawing of the large rifle equivalent, the military number 34 primer, and it allows the finished primer height to be an astonishingly tall 0.135" when the anvil feet are included, so they are apparently not using short anvil legs on that one. I'll have to try to get a drawing for the number 41. In any event, there is more than one way to skin this cat.

The firing pin in the AR moves back and forth freely. It has no return spring to hold it back against its retaining pin, so it is, indeed, a floating firing pin by definition. A primer indent happens as the bolt cams closed, and the carrier comes to an abrupt stop against the back of the barrel extension. At that moment, the free-floating firing pin is traveling at the speed of the bolt carrier and has nothing else to stop it from continuing forward until it hits the primer except a small amount of friction with the firing pin tunnel. Note that the amount of firing pin protrusion your carrier group assembly produces upon a hammer strike has no bearing on the depth of the indentation during bolt closing because the primer cup stops the firing pin well before it becomes fully extended.

Your gun's proneness to producing slamfires is affected by several things. The stiffer your buffer spring, the lighter your bolt and carrier assembly, and the better your bolt carrier group is lubricated for travel speed, the faster it will close and the bigger the indenting force on your primer will be in proportion to the square of that velocity (in proportion to the firing pin's kinetic energy). The heavier your firing pin is at the carrier group closing velocity, the more kinetic energy it will have in proportion to its mass.

If you look at the military H-test specifications for number 41 primer's sensitivity, you find the mean kinetic energy of ignition is 0.185 ft-lbs (35.5 oz-in; there are 192 oz-in in a ft-lb), which occurs when a 3.94-ounce steel ball is dropped 9 inches onto a firing pin resting on a primer in a holder that simulates a primer pocket. All primers tested are expected to ignite if the drop is from 15 inches, and none if the drop is from 3 inches. In reality, you get an ignition distribution, and the spec actually calls for the 3-inch drop to be three standard deviations below the mean value and the 15-inch to be three standard deviations above it, but I expect many actual primer lots beat those standard deviations.

My past experience hearing guns slamfire when the command to load is given at large matches caused me to estimate they occurred about once in 5000 loadings for a mix of M1 Garands and M14/M1As shooting whatever ammo the owners had brought with them; mostly, it is due to high primers. I've been present for one slamfire with government M2 ball on the load command out of about 100,000 loadings witnessed at matches where M2 was still issued in the 1980s. I have no way of knowing how many times these guns may have doubled because doubling in military-style rifles is usually due to the shooter's grip on the gun, causing him to pull the trigger twice. The average AR has less frequent slam fire occurrences than that, but I don't have a number. I can say a few people, like the one in the link I put up earlier, can have regular slamfires, probably due to too much closing speed in the gun from a high-power buffer spring or other mods that increase the carrier operating speed.

[Shadow9mm]

for 22-250 Here are the results of my limited search. While the majority do seem to be 1:14, they do do as fast as 1:9, and 1:10 to 1:12 seems to be fairly common.

Bergara 1:9
CVA 1:10
Ruger 1:10
Weatherby 1:12
Savage 1:12
Remington 1:14
Tikka firearms 1:14
Howa 1:14
Christensen 1:14

But my point was, in general, a manufacturer will generally not load a bullet in a way which will create the grey mist. Its loaded in 22-250 at higher speeds, albeit with a slower twist. And it is loaded in 223 at normal 3240fps speeds. So one would expect you would have to push things a fair bit faster to get them to come apart. Especially if your talking FMJ, not varmint bullet.

[georgehwbush]

( ... would expect you would have to push things a fair bit faster to get them to come apart. Especially if your talking FMJ, not varmint bullet. )
i agree. but how many people buy an ar15 with the intent to only fire 55fmj and of those how many stick to that plan and don't test other ammo looking for better accuracy... and that is a bit of a moot point anyway. the fact remains that some do take into consideration the posibility of over clocking the lead, when considering twist rate. one would be wise to consider all aspects of internal/external/terminal ballistics when choosing a firearm/ammunition combo. and i understand that the majority do not.

[coyotes220]

I'll try posting my question here, hopefully I'm not out of line.Does anybody know a quickie hack to get around having to buy the expensive 9.3x72r dies for my new to me so chambered rifle? Fwiw, I'll be running very low pressure so FL resizing shouldn't be required too soon anyway.

[georgehwbush]

coyotes220 there should be a bushing neck sizing die that will work but i'm not versed in which one. and something like a hornady universal seating die maybe. there are universal decaping dies too.

so are you looking to use what you already have; or, is it a search for anything that will work because shell specific dies are hard to find ?