I need help, what's wrong with my chamber?

[ElkPRC]

I just had a new Bartlein Carbon Barrel that was chambered in 6.5 PRC, I will leave the gunsmith unnamed. Barrel was fit onto a Bergara Premier long action.

I took the gun to the range and shot just a handful of factory Hornady 147 match ammo and every round came out with this bulge. Th base of the case webbing area is .529in and on the bulge it is .5335. The bulge also only goes 180 degrees around the case.

Kicker, this is the second barrel this has happened with. It happened on the first one, I sent the barrel back we both thought the chamber was cut incorrectly and the barrel was redone. Second barrel comes and there is the same exact issue and brass looks identical. Let's assume the gunsmith did cut a new barrel and not just send me back the previous barrel, what would cause the brass to do this and present the same exact way with both barrels. The gunsmith says he is positive he cut the chamber correctly this time as he put special attention to it after the first.

The smith also says this was cut with the .535 wider bodied Wheeler 6.5 PRC reamer to fix a lot of the early issues that were happening with chambering 6.5 PRC.

Lastly, this action has held and fired other barrels in the past with no issue, misalignment or mis-formed brass. I would think this would eliminate that as a variable, but I don't know. I've thought of the extractor possibly holding the case improperly, but wouldn't that have done the same with previous barrels?

Welcome any and all feedback you may have I need to know if this is the gun smith or possibly something else.

 

[huntnful]

The case is just swelling to meet the new chamber dimensions. The swelling stops right that in area normally because that’s where the brass starts to thicken. It probably looks so prominent because that brass is junk. Normally it shows up as more of a gradual faint line on a piece of Lapua brass.

That wider chamber is only necessary if you’re going to be reloading fired cases,
not just shooting factory ammo. And I definitely wouldn’t recommend reloading the Hornady brass.

 

[huntnful]

Here’s a case fired in an intentionally oversized chamber. The Lapua sized cases need to be able to be squeezed down quite a bit to avoid clickers on subsequent firings. So the oversized chamber helps let them grow outward a little, so that the sizing die can then squeeze them down much more, for the following firing.



Basically your chamber is just big, so you can avoid issues while reloading. And after 2-3 firings the brass would be mostly formed all the way outwards, and that line wouldn’t be so prominent.

 

[ElkPRC]

I agree with all of that completely, my counter is this.

I have shot plenty of Hornady ammo before and while I agree on their quality of brass I have never seen anything more than you discuss which is a faint line. this is a 4-5 thousand bump(and a crooked uneven one at that) I have also never seen where the swelling is only happening on 1 side of the case and not the other.

I can take a dental pick and feel the center part of the line on the inside of the case. This is nearing case head separation as the case stretches on just one side and not the other. It's this that seems very unnatural and concerning to me.

 

[ElkPRC]

Here’s a case fired in an intentionally oversized chamber. The Lapua sized cases need to be able to be squeezed down quite a bit to avoid clickers on subsequent firings. So the oversized chamber helps let them grow outward a little, so that the sizing die can then squeeze them down much more, for the following firing.

View attachment 685715

Basically your chamber is just big, so you can avoid issues while reloading. And after 2-3 firings the brass would be mostly formed all the way outwards, and that line wouldn’t be so prominent.

Thank you for the photo and explanation. All makes complete sense and while I can get over how prominent the bump is i can't get over why it only half way around the case and curved at the bump end point. To me this means either the round is held off center or its expanding to an off-center camber.

Am I wrong in my thoughts or concerns with this?

 

[ckleeves]

Is your ejector plunger hung up some how and not depressing flush with the bolt face? That could put pressure more to one side than the other possible causing the 180 vs 360 line?

 

[huntnful]

I agree with all of that completely, my counter is this.

I have shot plenty of Hornady ammo before and while I agree on their quality of brass I have never seen anything more than you discuss which is a faint line. this is a 4-5 thousand bump(and a crooked uneven one at that) I have also never seen where the swelling is only happening on 1 side of the case and not the other.

I can take a dental pick and feel the center part of the line on the inside of the case. This is nearing case head separation as the case stretches on just one side and not the other. It's this that seems very unnatural and concerning to me.

Have you check how much to shoulder has grown forward? It would take a while (several firings) to get case head separation I would think. Even if it was chambered extremely long.

And my theory with the bump being more prominent on one side (it does it slightly in my oversized Lapua chambers also) is that the case is basically floating, in the now larger than normal chamber. When it’s fired, pressure forces it to one side of the chamber and it grows more on one side of the case to fill the opposing gap. I don’t believe the case stays perfectly centered, and grows perfectly centered in the large chamber. That’s totally a theory though. But I’ve had 6 oversized Lapua chambers, and they all form brass the same way. With more firings, everything seems to smooth out more and more though

 

[ElkPRC]

Is your ejector plunger hung up some how and not depressing flush with the bolt face? That could put pressure more to one side than the other possible causing the 180 vs 360 line?

How would I test for this?

 

[wind gypsy]

Spitballin here but I could imagine how a case would get pushed into a chamber and be resting on the bottom of chamber with most chamber to brass clearance being on top of chamber. Upon firing the case head is pushed back hard against the bolt face so it is less likely to be perfectly centered when case expands to fit chamber?

 

[ckleeves]

Just push in on the ejector plunger and make sure it moves freely. If there is any ejector marks on your brass you could see how they index vs the line you’re seeing on the brass to see if there is any relationship between the two. Normally a stuck plunger will mark brass a little even on low pressure loads so if there isn’t any ejector marks it’s probably not that.

 

[huntnful]

Spitballin here but I could imagine how a case would get pushed into a chamber and be resting on the bottom of chamber with most chamber to brass clearance being on top of chamber. Upon firing the case head is pushed back hard against the bolt face so it is less likely to be perfectly centered when case expands to fit chamber?

Another great theory on the offset case growth. I don’t know exactly why it happens, but it for sure happens hahaha.

 

[BULLBLASTER]

The ejector is always pushing on one side of the case head, even if the bolt is closed. The case is being pushed down toward the bottom of the chamber when it is closed. Then rotates so that pressure can eject it out of the action once opened. The cartridge doesnt just rest in the chamber.

 

[ElkPRC]

The ejector is always pushing on one side of the case head, even if the bolt is closed. The case is being pushed down toward the bottom of the chamber when it is closed. Then rotates so that pressure can eject it out of the action once opened. The cartridge doesnt just rest in the chamber.

That would be my thoughts as well. I understand there are clearances in chambers but not that much and if you just place a loaded round in a chamber with the barrel off and try and wiggle it or even pull it back out with just finger nails it's pretty snug (In general not speaking to this barrel I haven't tried that yet).

So @BULLBLASTER with what you are saying and the case head being held in place, what do you see as a potential issue here?

I am not a pro or an expert but I have fired more rounds than I can count on almost as many guns and never seen uneven case marking like this or as severe of case markings like this., with the exception of a M249 post case head separation, hence where my worries in this are founded from.

I mean it's almost ,005in of a bump that is very uneven, am I crazy to think that's out of the norma and something to be worried about.

 

[ElkPRC]

Just push in on the ejector plunger and make sure it moves freely. If there is any ejector marks on your brass you could see how they index vs the line you’re seeing on the brass to see if there is any relationship between the two. Normally a stuck plunger will mark brass a little even on low pressure loads so if there isn’t any ejector marks it’s probably not that.

I will check this later and report back. Thanks for the info

 

[BULLBLASTER]

It almost looks like there is an imperfection in the chamber at that point to me and brass is flowing into it. Can the brass be sized and reloaded? How does it shoot?

It looks much closer to the case head than the example huntnful posted, and looks like it would still be in tue thick case head to me.

Can you post more pictures?

 

[wind gypsy]

That would be my thoughts as well. I understand there are clearances in chambers but not that much and if you just place a loaded round in a chamber with the barrel off and try and wiggle it or even pull it back out with just finger nails it's pretty snug (In general not speaking to this barrel I haven't tried that yet).

What's a AW2 chamber spec at the 0.200" line, 0.534" or 0.535"? Your brass is measuring less than that.

No idea on the "is it safe" front but interested to hear what others say. I wouldn't be very happy with that result either.

Do you have a bore scope?

 

[ElkPRC]

It almost looks like there is an imperfection in the chamber at that point to me. Can the brass be sized and reloaded? How does it shoot?
It looks much closer to the case head than the example huntnful posted, and looks like it would still be in tue thick case head to me.

Can you post more pictures?

I can post more picture later. I figured it is a chamber thing as well but want to be sure as the gunsmith has already replaced the barrel once for this and thinks it’s not the chamber.

It shoots like shit 2 inch groups, but take that with a grain of salt it’s only the first 8 rounds fired on the gun and then I stopped.

Have not tried reloading or sizing the brass, frankly was just going to throw the Hornady brass away I just use a few boxes of factory to get the round count up a little before bringing out the Lapua brass and hand loads.

 

[ElkPRC]

What's a AW2 chamber spec at the 0.200" line, 0.534" or 0.535"? Your brass is measuring less than that.

No idea on the "is it safe" front but interested to hear what others say. I wouldn't be very happy with that result either.

Do you have a bore scope?

I do at home but I am traveling currently so can’t look.

What would you like to see under scope?

 

[wind gypsy]

I do at home but I am traveling currently so can’t look.

What would you like to see under scope?

It sounds like something that could very well happen in a standard AW2 spec chamber if the brass expands easily there. It's always nice to be able to look at it and see if everything looks good.

 

[BBob]

Brass case wall and web thickness is almost never uniform no matter how good your brass is. The bulge initially appears on the thin side. Does anyone really think a little spring can overcome 50K psi or more of chamber pressure to influence how the case expands?