Reloading for freebore

[Mtns2hunt]

I have two older rifles that I love to shoot. One a 30-06 Browning A-bolt 2 and the other a Sako Finnbear 7mm mag. Freebore is increasing in both rifles and I am trying to reload to take the freebore into consideration.

I am sub moa on the 7mm with no change in my seating depth. The groups on the 30-06 are starting to open up and are currently 2 MOA although I am working on seating depth to tighten up the groups.

Wondering what my options are: rebarrel, continue to play with seating depth? I am not sure I fully understand the freebore issue as Weatherby has a lot of jump so why would extra freebore matter. Cartridge line up and accuracy seem good.

These are hunting rifles so some accuracy loss is acceptable.

Thanks for any feedback.

[44 AMP]

First off, let me point out that there is a big difference between freebore as an intentional feature and "freebore" that is the result of barrel throat erosion.

IF you're sub MOA with your 7mm Mag, hunting rifle, "it ain't broke and don't need fixin'"

A 2MOA big game rifle will put meat in your freezer, year in and year out.

There are lots of things that can cause groups to open up. Barrel wear is just ONE of them. Sometimes the reason is as simple as screws that have loosened (action screws, scope mount screws, have been known to do that) or warped wood....

If its the barrel throat, a borescope examination will show it.

Loading bullets out so they are closer to where the lands are now might cure the problem for a while. Might not, also. IF the barrel is too worn, options are rebarrel or having the original barrel set back and rechambered, if possible.

Good Luck!

[Unclenick]

In addition to what 44 AMP offered, I will point out the idea that short bullet jump is an essential ingredient to accuracy is something that was assumed to be true because a lot of benchrest competitors either jammed bullets in their rifle throats or swore by one particular short jump or another as a universal truth for accuracy. Subsequently, this has all gone out the window.

The first clue I recall was in the 1995 Precision Shooting Reloading Guide. Benchrest competitor Dan Hacket described a 40X 220 Swift he could not get to shoot 5-shot groups into under 3/8". At the time, he was subscribed to the idea 0.020" of bullet jump was ideal and loaded all his rounds that way. Then one day, while switching bullets, he accidentally turned the micrometer on his seating die the wrong way and loaded 20 rounds 0.050" off the lands. When he fired them in groups of 5, he got two 1/4" groups and two true bugholes in the ones. So much for 0.020" off the lands.

The second clue was an online article describing a program Somchem used to have at their facility in which they would tune loads for a customer. One day they had a fellow show up with an old 8 mm Mauser with a badly worn throat. It looked shot out to the Somchem tech, but the fellow said it had belonged to his grandfather, and he wanted to hunt with it again for sentimental reasons. So the tech worked up a load and started moving the bullet back. Every time he moved it back, the group got smaller. In the end, the rifle wound up shooting the smallest groups ever seen in the development program. Some like 1/3" C-T-C or a little better, IIRC.

The third thing was this article by Berger that came out before their hybrid bullet ogive came out. Similar findings for other bullet types and by other folks testing the concept started to show up. Scott Saterly, a top-ranked nationally known precision rifle competitor, has said he's now loading about an eighth of an inch back from the lands.

The bottom line is that if you load to maximize cartridge concentricity, have a concentric bore and chamber, and get your brass loaded without too much head clearance, you likely have all the aligning you need, freeing you to try different seating depths, as the Berger article suggests. I have a theory about why benchrest competitors held to the short jump for so long, but I don't want to go into it here. Suffice it to say it was overdue for challenging long ago. In your shoes, I would go the Berger route but probably reduce the initial step size to 0.020" if you are not shooting the long VLD nose profiles. Shorter profile, shorter steps. This is because the annular gap between the bullet and throat increases more quickly with seating depth using a stubby ogive vs. a long one. Dr. Lloyd Brownell demonstrated way back in 1965 that this affects pressure by how readily it vents bypass gasses as the case neck opens under pressure.

[Shadow9mm]

I follow Erik Cortinas philosophy. His idea is that there is o point in chasing the lands. That barrel harmonics are the key factor. He tunes in 0.003 increments for seating depth. This adjustment effects the timing of the bullet leaving the muzzle due to the change in distance to the muzzle. Kind of like a pendulum you want to catch the barrel harmonics at the top or bottom of a swing so that the bullet leaves the barrel at a point with minimal movement increaing consistency. And there are several good nodes, like a sine wave, that you can find, depending on how far you adjust the seating depth.

If it were me, id tune seating depth. Load 0.003 and 0.006 long and short and see if you can get into a better node.

[Mtns2hunt]

I wish to thank everyone for their excellent feedback. My tightening of groups is more of a confidence builder for my self than anything. I enjoy reloading and working up loads. So far this year I have worked up my 22k Hornet and 243 browning. I just like those sub MOA groupings.

However, some of my rifles are aging and I would like to keep them in top shooting condition. I do not shoot the sako much anymore preferring to save it for out of state hunts. The Browning has been my main hunting rifle for the past 15 years or so and does get a good workout each year in state and out.

On the browning I cannot measure to the rifling as the AOL gauge will not adjust far enough out or I need a longer bullet. Currently shoot Nosler partitions in it.

I have checked scope screws, mounting screws, action screws and barrel float. All is in order. All the feedback has reinforced my belief in ladder testing seating depth. Rebarreling or "original barrel set back and rechambered could certainly be last ditch options.

Couple buddies suggested I trade in my old guns and buy some of the newer rifles and cal on the market. But I am old school and prefer older calibers. Love my 220 swift. I appreciate the feedback and knowledge shared. While the options are rather limited I will continue to play with all the variables and especially the bullet depth. I will post my results.

[Shadow9mm]

Fact it, barrels are disposable, they wear out no matter what you do. Even actions can wear out, given enough time.

For me this means 2 questions.

1 what are your accuracy standards or expectations, because that will determine when the barrel is done, not wear in the barrel itself.

2, when a barrel wears out, do you have a new barrel put on, get a new gun, or have the barrel set back and a new crown put on. Personally i would put on a new barrel or have the barrel fixed, unless its significantly more expensive thsa buying a new

[tangolima]

One more option is to have the barrel set back. It removes some of the throat erosion and excessive headspace developed, should there be any. A competent smith can do it for fraction of cost of a new barrel.

The way I understand it, bullet jump determines the location of the pressure peak and hence changes the poi consistency. Unfortunately the range for adjustment is usually limited by other factors.

-TL

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[Unclenick]

I don't know if the Browning can be set back. One of the complaints about the A-bolt (and, I assume, the X-bolt as well) is that Browning uses some kind of super-strength thread adhesive when they install the barrel. As a result, only the factory can change the barrel, and someone suggested they can't actually change it without damaging the receiver, either, so they destroy the original and reissue the serial number on a new one. But I only have that as hearsay and haven't asked Browning.

I also have an A-bolt in 30-06, but it's not my main hunting rifle. I got it for experimenting with the BOSS tuner and haven't put much mileage on it, and I don't anticipate shooting it out. I've forgotten its throat length. I'll check. If you have or can borrow a 240-grain MatchKing or similar long bullet, that may solve the measurement issue. I'll try it and see what I come up with. In the meantime, you might consider getting one of these so you can see the actual condition of the throat.

[Mtns2hunt]

"I found this on another site while doing an internet search.

"Since making this post I have been in contact with the R&D Department of Browning.

The tec that I spoke with could not tell me if the actions were investment cast. He said he would find out and call me back.

He verified the threads had been changed from 20 tpi to 32 tpi.

He said no glue was use to lock the threads.

He said with the appropriate wrenches and technique the barrel would screw right off the action. He said he had done thousands of them.

He said the actions did have an anti seize compound on them.

He could not have been any nicer and appologized for the persons lack of response from their Browning service center.

The wrench from Brownells should be here today."

Also found several gunsmiths that will to do the exchange. Main issue seemed to be finding Browning barrels due to thread pitch. How ever I do not see much difficulty getting a barrel machined to the right pitch if necessary. However rebarreling or having the barrel set back are last resort actions. I would prefer to narrow groups by working with bullet seating. Seems to me I should be able to find a node farther out that would work.

I do require all my rifles be sub MOA not for any real reason other than it builds my confidence and I shoot much better being confident in my rifle.

Again thank you for everyone's input. It helps a tremendous amount to understand what everyone else is doing and their thought process in doing so.

[NHSHOOTER]

What an excellent discussion on freebore, I for 1 was of the less jump the better school of thought and most of my rifles seem to like it, I do have a Kimber 7-08 that wouldnt group less than 4" and I was dumbfounded, tried several weight bullets without much success until 1 day last winter I started seating them 10 thousands deeper and guess what, it got better, I dont have it under 1" moa yet but its getting closer..Thank you all for the excellent input.. I do believe each rifle has that 1 sweet spot and the fun is looking for it and finally finding it..

[Unclenick]

Mtns2hunt,

Thanks for finding that information. Glad to have the hearsay blown up. It never made sense, in principle. The action wrench will need to have the right adapter to fit the action without scuffing it, but that's the only special element I can think of.

Obviously, if you can buy a barrel blank and put any thread you want onto it. I expect the custom makers who offer contouring can either put it on for you or leave the tang unthreaded but do the rest of the contouring at your request. The gunsmith can thread it on his lathe. Why Browning put such a fine thread on a barrel, I have no clue, but it is what it is. Douglas Barrels has a profile lathe that will copy any contour, so having your gunsmith pull your old barrel so you can send it to them to get a blank made and contoured to match it would be an option. Their shop is all CNC, so I would expect they can copy the barrel threads as well.

As soon as I find where I hid my 30-06 case adapter, I'll go after the throat dimension.

[tangolima]

Ah one of those eh? Some said a thin releaf cut on the barrel shoulder will undo it. But the barrel will be ruined. Installing a barrel with the crazy medicine opens the door for next time.

-TL

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