Why does my bolt open/close hard?

[Bubba]

Somebody please help me out. I went to the range to check things out before my annual Pdog trip. My gun is a 6BR 12 twist shooting 32.2 gr. Varget behind a 75 gr. V-Max with new Lapua brass. The bullet is seated 0.010 from the lands. After the first round down range I noticed that the bolt was hard to open. I looked at the case head and saw no cratering or flattening of the primer and no extraction marks on the case head. Fired two more rounds with the same result. The three shots printed a nice bughole and velocities were normal (3200 fps). This is the same load that I have been shooting with the same lot of Varget and the same lot of 205M primers. I figure that it is time to quit and do some investigation. ???

My chamber has a .272 neck and loaded rounds measure .268-.269.

OAL case length is ok.

Bolt closes easy with go gauge and will not close with no-go gauge.

Next, I take a new piece of brass and try it and notice that there is some slight resistance to closing the bolt. ???

What am i missing here?
Any help will be greatly appreciated.

Thanks,
Bub

 

[clowdis]

Do you have a 6BR Remington chamber? Are you using Norma or Lapua brass? If so, the chamber might be a little bit too tight and you need to ream it with a 6BR Norma reamer, especially if brand new brass is too tight to fit. Aside from that make sure you're setting the shoulder back far enough on your resized brass. Also try running the new brass through the full length sizer and see if that helps.

 

[Bubba]

Clowdis, thanks for the reply.

My barrel is a Shilen and the chamber is a 6mm BR Norma w/ .272 neck. I screwed the barrel onto a Savage Target Action and used a set of go/no-go gauges that I got from Brownells. Could it be that the gauges are for a standard (Remington) 6BR making the chamber a crush fit on new Norma brass and causing the hard bolt lift on fired cases?

Bub

 

[clowdis]

Headspace is the same. The diameter is a little bit larger for the Norma. Sounds like the headspace might be just a little bit snug which is fine if the "go" gauge fits so try the body die and see if that solves the problem.

 

[gambleone]

Clowdis, thanks for the reply.

My barrel is a Shilen and the chamber is a 6mm BR Norma w/ .272 neck. I screwed the barrel onto a Savage Target Action and used a set of go/no-go gauges that I got from Brownells. Could it be that the gauges are for a standard (Remington) 6BR making the chamber a crush fit on new Norma brass and causing the hard bolt lift on fired cases?
In your first post you said you were using lapua brass & this post states norma? I would drop the charge to 31.9 gr & see if you still get a tight bolt lift. If you neck size & this brass has been fired about three times, you might want to bump the shoulder back a tad.

Greg
Bub

 

[fdshuster]

Bub: I had the same problem when re-installing a Hart 1-8 twist 6BR, .272" neck. Go-Gauge was chambered, barrel screwed on 'til firm contact with the go-gage, and when tightening the barrel nut, the receiver would move a very small amount. Just enough to change my previous headspace length. Since all my 6BR chambers use the same headspace on the fired brass, ( 1.157"), and I don't want to keep changing the Redding die, I unscrewed the barrel, and tightened the nut again. This time, headspace was the same as before the barrel was removed. The main reason I prefer my Rem. 700's for switch-barrels, and the next Savage barrel will be fitted with a fixed barrel/receiver joint like the Rem 700's---- no barrel nut. Your problem may be the same change in headspace length.

 

[fullersson]

It sounds to me like you should leave everything like it is and be thankful that you accidentally installed the barrel correctly. ;D I'm just kidding about accidentally installing the barrel correctly, but alot of shooters (myself included) prefer a crush fit and if I shot a bughole with 3 shots I would leave it alone. You should shoot the gun at long distances and see how it is grouping. I have a Savage target action that I set the headspace back on to get a crush fit; the short range groups improved but the longe range groups aren't as good as they were before I set the headspace back. Some people may not agree with that statement but it seems to have happened to me. I plan to do more testing to see if it is true. Good shooting. Brian.

 

[long40shot]

Hello,

Could it be as simple as your brass needs trimmed? Just a thought.

-Matt

 

[Bubba]

Gambleone-Sorry for the confusion. I am using Lapua brass.

fdshuster - you have probably hit the nail on the head. The problem with the hard bolt lift on a fired round started after a barrel switch. I'll try resetting the barrel and make sure that the receiver doesn't move when the nut is tightened.

fullersson - thanks for the input. So far, in the limited testing that I have done, the gun is averaging slightly over 1" for 3 shot groups at 300 yds. Kinda reminds me of the old saying "if it ain't broke don't fix it" :-\

 

[therifler]

could be your brass expanding and not snapping back after you fire them .if it was the barrel change you should know your next trip to the range . good luck with your troubles . T.R.

 

[camac]

Also check for donuts. But sounds like the chamber might be "smaller" (or tighter match chamber) especially with perhaps some reduced head space so pressure might be up slightly. If this is a new barrel you should do your load development again. Most chambers and barrels are different.

 

[wapiti25]

I would like to caution any one puting a 6mm BR Norma reamer in a 12 or 14 twist barrel, you may get a throat that is too long for the 70gr or about that weight bullets. I'm in the process of rechambering a barrel that went from a tight neck to a no turn neck. the Norma chamber is more for the 105gr bullet throat.

 

[Old Navy]

Bump the shoulder a little. Later! Frank