Bolthandle randomly Stiff 6BR

[matorre]

I am at my wits end.

I am puzzled about my new 6br, and my new brass.

This gun is brand new , with brand new brass. Brand new Krieger 1/8 twist.
It goes across the course

My problem is in the rapid fire stage with the new gun/ brass. When shooting rapids about 1 in 5 or sometimes 2 in 5 the bolt is very hard, or gummy to lift. Distracting. Disconcerting.

This effect started with NEW brass, and continues.

The load is Varget 28 grains, Lapua brass, CCI 450s, and SMK 107s'.

I am .025 off the lands. Was new brass.
I am halfway through the second firing of the brass.
Tried 29 grains. Not good.

Tried polishing the chamber.


Went back to the 'smith, and we went from 0.00 headspace to 0.0025 headspace to get a little room on the go gauge

No change. Everyone else is running 30 grains. This has a new Krieger barrel 30" finish length, normal groove/bore. Chamber is .2718 on the chamber sheet. (PTGReamer ).

Sizedfull length on Forster full length sizer. Drops right into a Wilson Cartridge gauge.

Fired case .271. loaded case .268

The gun shoots great regardless of me fiddling with things.

Must I shoot 26 to 27 grains.................... ?


Regards
Michael Torre
Southwestern Virginia

 

[jo191145]

Two different animals but,,,,

My first 30BR did exactly that.
I chased my tail for quite some time trying to figure out what and why.
Eventually after a thorough annealing the problem stopped and never returned.

Obviously two different animals but,,,,, keep it on your list of things to try.

I would segregate your sticky brass and conduct an expieriment.

 

[gme]

Does the rifle close easily on ALL of your sized brass?
Gary Eliseo

 

[matorre]

Closes very easily. If the bolt is stripped, it will drop.

.200 up from base, fired cases are .4702 to .4705

and resized cases are .4698 to .4700 at .200 up from base.

Michael

 

[timeout]

The load you are shooting in a 6BR should not be the problem. Try dropping back a grain and then two, to see if the problem goes away. Sounds like there is an issue with the rifle. May be a stupid idea, but are you certain the powder scale does not have an issue? I have only ever owned one 6BR, but your load sounds OK. Also wondering if your trim length is correct for the chamber? That would be easy to check. I just read that your bolt drops when stripped, so trim length must not be an issue.

 

[matorre]

I have 4 scales, that I check one against the other for paranoias' sake.

I check the check weights, and the loads on all.

Lands of the rifle barrel gauge out at .236 useing a Deltronic pin.

Chamber is round, concentric and perpendicular to bore, and smooth.

Michael

 

[243winxb]

cci 450 Mag primer-more pressure? The cci400 is soft/thin, i would not use them at max pressure. Maybe try CCI BR4, or Rem 7 1/2 ?
Rapid fire-more heat? All a guess, dont own one.

 

[memilanuk]

I'm kind of a like mind as the first responder (jo191145)... does the problem seem to track back to particular cases? i.e. if you find a case that sticks, can you sit it aside and then next time you reload it does it stick again? Have you looked into annealing the cases - how many firings on these?

Something that I've used to see where a case is hanging up in a chamber is to coat it with a black Sharpie and then inspect the ejected case to look for rub marks. Granted, this is something I normally use for guns that have issues *chambering* ammo that should be in spec, but it might work during the firing process as well.

 

[Terry]

Did you find out what it was?

 

[matorre]

I haven't yet found a good way to sort brass during the
rapid fire strings with a bolt gun.

I can do it ok, with a semi-auto, but that is a different story.
: )

Michael

 

[gme]

Michael,
Is it possible that there's some case lube residue on some of the cases? I've seen that cause similar issues.
Gary Eliseo

 

[Shynloco]

Michael,
Don't know if this helps any, but I was fireforming my new Lapua brass this morning using a close combination to yours: Sierra 107 SMK's being pushed by 28.1 Gr Varget, Small Federal Match Primers with the bullet seated just touching the lands/Ojive seating measurement of 2.870, cases trimmed to 1.551 - no problems opening the bolt on a Savage Model 12 Benchrest rifle that I've had almost 2 yrs now. I use an RCBS Precision Mic (22-250 w/custom insert for case length adjustment to match 6mm casings) to make sure each and every casing has the identical shoulder settings. They usually require only a .001 - .002 shoulder bump after every firing in this rifle that is not a custom chamber which it sounds like you have with that Krieger barrel. I'm wondering how many rounds you've put through this rifle and if there is a bolt face issue or if your shoulders are inconsistent in resizing. Otherwise, have you looked closely at your primers to see if there are signs of pressure? In a rare instance, I have seen using the wrong primers on certain rifles have caused similar issues in heavy bolt lifts occasionally that was just a quirk of the rifle. One other thing I'd have checked is to have your Gunsmith (or you) use a set of PTG Go-NoGo gauges and see how the bolt feels upon closing using the gauges. Good luck and hang in there.

Alex

 

[jimbo88mm]

A little lube left on the case is a good thing to check.

I've also encountered this if a little wipeout gets into the chamber and is not cleaned out. With the wipeout the symptoms are different though... usually the first few rounds have the stiff bolt, after that it clears up.

 

[BoydAllen]

Sometimes if the body diameters of a chamber are too close to those of an unfired case, problems such as you have described will occur. I believe that close control of headspace, neck diameter, throat diameter, and length are desirable, but sometimes smiths spec out their reamers too close to the size of unfired brass. This can require a custom FL die to get enough sizing at the base of the case, especially after repeated firing, and even if cases chamber easily, they can still get tight with loads that should not cause the problem. A friend had a similar problem and he had the barrel set back and rechambered with a reamer that had more room in the body. That fixed his problem.

 

[matorre]

Gary-
Assureedly no lube, or die lube is on the case. I wet wash in soap water and tumble in water when done.



Everyone-
What dies are every one useing ? How small does your base get ?

I have Redding, and Forster. Are dies an issue in this caliber ?

Could the brass be too soft ? ( a real stretch for sure )




Boyd-
I am at .470 +/- .0003 on the sized case. haven't got the PTG reamer specs yet. Edited.... Its a JGS, and the base is .4714.

SHOULD be roomy enough, but its NOT, apperently.


I use a headspace gauge, but apparently that will not tell you whats going on with the base.

Who sells "widebody" reamers ?
Prolly a custom grind, I bet.


Alex-
I shy away from reading too much into the small rifle primers.....having said that though, the have nice big fat radii.

Donovan-
Bolt timing is good. Issue happens on the upstroke. No carbon ring.
bolt is like new. Brass is new. No carbon.

Thanks,


Michael

 

[rlandrum]

I have a 6BR that does this with factory Lapua loads (about 2 out of 20). It's the bolt and extractor rubbing the bottom of the cartridge. This is because the necks are just a hair too thick in some dimension, usually because of how the round was seated which slightly distorted the brass, which prevents the cartridge from turning inside the chamber as the bolt presses against it. Turn the necks, or just use some fine sandpaper to smooth them back to round.

If you cover the round with permanent marker (let it dry), you can see clearly where it rubs on your barrel, camber, and bolt.

Rob

 

[dansig]

I haven't yet found a good way to sort brass during the
rapid fire strings with a bolt gun.

I can do it ok, with a semi-auto, but that is a different story.
: )

Michael

since you are only shooting 5 rounds at a time mark your cases 1-5 and shoot in that order, when all 5 rounds have been shot pick up your cases and put aside those that aren't ok.

only shooting 5 shots you can't forget if it was case 3 or 4 that wasn't right..

 

[matorre]

Rob-
I have .003 neck clearance. My issue is that this would
even happen with brand new out of the box brass.

Putting the cartridge on the concentricity gauge
would always assure me of a round cartridge.

Michael

 

[LongRanger]

From what I read thus far I don't suspect anything wrong with the chamber. Honing it out big enough to eliminate the issue could poss work since extra space is being given for the case to shrink back so that it clears......but just may be masking the real issue.

Before going that route, check these things.

Does bolt reclose easily on a just fired sticky case while hot? After cooling without stripping bolt?

At home, with the bolt stripped, I rechamber every fired case and segregate any which enter chamber with more than minimal amount of resistance to sliding past the extractor. They go into the "foulers only" pile

Check new and fired brass for case head and body not being on same axis (means checking to see if case leans when base is flat on horizontal flat surface...not same as checking for case roundness). I use a NECO measuring set to do this. New brass and fired brass sized down to the web mask the problem that off-axis can cause since they often go into the chamber freely if only minimally misaligned. But upon firing the bottom of the cartridge closest/touching the chamber above the web swells and can bind against chamber wall. This problem never goes away with repeated firings.

I toss all cases over .003 (over .004 will bind going into my chambers...smithed by Greg Tannel) for this issue.....which has amounted to as much as 60% rejects on some US made brass. (Less than 1% with Norma). Don't know about Lapua, but I would still check.

Frank B.

 

[matorre]

i noticed a very few pieces of brass that are not "square" with its base, also has a thin spot running up the side. makes good sence. explains the odd banana cases.

Not all "stickies" are bent.

Bolt timing is perfect.

I find it odd this issue is in a precision biult bolt gun in 6BR,
since this issue is in no other bolt gun of my collection.

Especially those guns that shoot a lot of trash,(odd brass, hastily prepared)
in thier day to day work cycle.

But.....................

I am having troube getting my head around the "expansion" issue.

1) if the chamber is HUGE, the brass expands till it fills the chamber, then it contracts, and extracts. ( provided it doesn't burst or split)

2) if the chamber is SMALL then the brass expands till it hits the chamber walls, but doesn't contract enough, and therfore won't extract.

In my ignorance, what am I failing to understand ?

Michael