6 BR split necks

[TRECustom]

My first time to ever fire a 6 BR. Didn't even have it in a stock. Just lashed it down to a Lead Sled to start barrel break-in. Fired a round of Rem 6 BR factory 100 gr ammo and had several neck and shoulder cracks. Easy to chamber and easy extraction. No signs of pressure or visible case expansion, so fired another one. Did the same thing so I stopped on it and shot some other rifles. When I got home, I measured the fired cases against unfired rounds and found normal case growth. Seems unlikely, but could it be something wrong with the Rem case necks? I'm probably going to finish off this ammo doing barrel break-in, then switch to handloads in Lapua brass. Anybody else had this happen?

Thanks, Tom

 

[Travelor]

Sounds like the brass has age hardened. I would anneal them before shooting. THis should solve your problem.

George

 

[fdshuster]

Tom: Necks hardened with aging seems like a good possibility. I'd be curious to know what the as fired case neck diameter is? Could the chambering reamer have cut an oversize neck dia.? What was your source of the Remington 6BR ammo? Are you positive it's new factory and not reloads? I'm just grabbing at straws here, throwing out "maybe's".

 

[flatlander]

I tried using some R-P 6BR in my first Dasher chamber, and stopped using it after 3 out of 4 rounds split at the shoulder. This is a much more radical use than your shooting them in a std. BR chamber, but it did make me wonder about how old the stuff was (bought it from Midway the same year I shot it - 2004). I've had Lapua BR cases split in the same way while fireforming in Dasher chambers, but the failure rate was 1% or less spread over 1200rds. in five different barrels.

OTOH, I've recently had several neck splits with once-fired Lapua BR cases in my Eliseo R5 tubegun's 6BR bbl., which I chambered with a .274" neck reamer. Wonder what's going on there - anyone else have similar experience?

 

[jo191145]

Me personally. I would'nt continue to use that factory stuff no way no how.
Pull the bullets and reuse them in Lapua brass for breakin if you wish. Gotta fireform those lapua anyway. Might as well do it now. Chuck that old Remy brass in the trash.

Seeing as theres no stock on the rifle I'd assume its a custom tube. Should'nt be much breakin required. Your choice tho.

Now if you see the Lapua brass split stop immediately and find out why.

 

[Steve Blair]

As Jo said, stop using that ammo, immediately. The risk of gas-cutting the chamber or worse is not worth a few rounds. Load your Lapua brass and break-in the barrel.

What would you do with the Remington brass anyway? There really is only one choice in 6 BR.

 

[msnations]

last I checked cartridge brass wasn't age hardenable. I'd start measuring the brass and check its hardness by some simple test (like using vice grips)...

http://media.photobucket.com/image/cartridge%20brass%20phase%20diagram/SlamFire/BrassPhaseDiagram.bmp

 

[jo191145]

Age hardened brass?? Way above my pay grade I'm afraid.

There are nitrates in gunpowder. Nitrates are made with ammonia. Ammonia causes brass to corrode and stress crack with time. I could be all wrong. I'm not paid for my brain.

A friend gave me about 300 loaded 30-06 rds about a month ago from his deceased brothers stash all mixed in a plastic bag. Besides the obvious "whats in them" component the brass is pretty well corroded. Ammo does go bad! Storage probably has a lot to do with it.
OTOH my Dad has a bunch of ammo from the WWII era. Looks shootable.

I still say try the lapua. One funny looking case and send the tube back for inspection.
I would do some careful measuring. Gotta do that anyway for sizing considerations.

Chuck the remmy brass.

 

[TRECustom]

Good info. I won't shoot any more of the factory Remington ammo. It is factory, probably old, and was given to me by a friend to use until I got my handloads done.

Frank, I am a little more confident that something is wrong with the brass itself, but will remeasure the 2 fired hulls and an unfired round to pin down the case growth, particularly the necks.

I just finished stocking the barreled action today. I re-inletted a single shot 40X stock for the single shot Mauser action, and pillar blocked and Steelbedded it. Came out pretty nice, but the combination of the big 40X stock and the 24" Harry McGowen bull barrel drove the weight up to 15 lbs, with a lightweight 4 x 16 x 40 mm scope mounted.

Thanks to all, Tom

 

[TRECustom]

Made it to the range today. Discovered that I couldn't bore sight because the heel and comb of the 40X stock are too high to see down the bore. Not wanting to burn any of my handloads, I used 2 of the Rem factory rds to get it to print 3/4" high at 20 yds. One neck had a short split and the other didn't split. I said I wouldn't shoot any more of them, but I obviously can't be trusted.

The 70gr Smkhp has possibilities. Shot 1/2 moa at 100yds cleaning between rounds. New Lapua brass, 33grs Varget and 205M's. Problem is that seated to a full caliber engagement (approx 3/4 neck), the bullet is .100" off the rifling. Seated to engrave the rifling, it only has approx .080" engagement in the neck because of the boattail. Looks like I need some flatbase bullets.

The 75gr Barnes yellow colored solid seated on the rifling with nearly full neck engagement, but shot about an 8" circle at 100 yds. 32grs Varget and 205M's. Not much of a future for this bullet.

Case O.A.L grew .005" with both loads. Necks grew .002" over the loaded round diameter, and the body (1/4" in front of the web), and shoulder grew .003" over an unfired case. On my hunting rifle loads, I'm used to a little more neck diameter growth, less body growth, and less case length growth.

With this info in mind, I'd appreciate more input from you guys that are familiar with this cartridge. I'm out of my element here.

Thanks again, Tom

 

[jo191145]

Hey Tom

First problem I see is your stock. If you can't see down the bore how are you gonna get a cleaning rod down it?

What is the twist rate?
What is the major use for this rifle? Target or hunting?

.080 "bearing surface" is doable for a target gun. Can't count the boat tail. Bearing surface seated in the neck is the relevant measurement.

Never had any 70gn Sierras so I know nothing of them. I'm quessing you have a tighter twist tube throated for longer bullets.

 

[TRECustom]

jo, I use a .22 cal rod and a throat saver. the rod rubs the heel of the stock, but flexes enough outside the boresaver to line up with the bore. No problem.

It is a 24" 12 twist bull barrel. I'll mainly punch paper if it is accurate enough. I'm only looking for sub 1/4 moa, and might use it to neck shoot turkeys that are way out of shotgun range. I am already enjoying it, but like Jack O'Conner said, "only accurate rifles are interesting".

I figured I would have to try the short neck engagement with the Sierra just to see what would happen. The action is a single shot, so the rounds don't get pushed up and out of a magazine. .080" probably will hold them in the case if I handle them gently. Yeah, that's bullet body engagement. The boattail shortens the bearing length by a good 1/8". I've got some 68gr Berger flat base bullets ordered. They sound like a good bet. Also will try some different powders.

Thanks, Tom

 

[fdshuster]

Tom: yes, me again/ different "wave length". The 75 gr. Barnes are probably too long/heavy for your 14 (?) twist. Both my 14"s (Shilen & Hart) also start to open up with 75 gr., but not to the extent yours did. I limit my 1-14's to 70 gr. bullet weight/length maximum. I also have several rifles with high comb stocks ( bell & Carlson Medalist/Tactical's), and when sighting-in a new mount scope, put up a large 24" square of paper & walk downrange to within 25 yds., fire a shot from a stable sitting position. Always puts me on the paper, somewhere, and I'm able to adjust from there. (note) O.K., just saw your post for a 12 twist: should easily handle a 75 gr., so fagetaboudit ( my comment about the 14).

 

[TRECustom]

Got the 68gr Berger flat base hollowpoints today. Loaded 5 rds with 32grs Varget, seated the bullet in the rifling with .118" neck engagement. 5 more with 31grs H-4895, same seating depth. 5 more with 31grs Reloder 15, same depth. Also jo, I loaded 5 of the 70gr Smkhp's seated on the rifling with 32grs Varget. Not much neck engagement, (.080") but am curious to see what they do.

By the time I finish this 20 rd session, the barrel should be seasoned if it's ever going to be.

I won't be able to get back to the range until after Thanksgiving, but will update when I do.

On the split neck question, Lapua brass has had no problems of any kind. I really like the tight primer pockets too.

Tom