6cm and the bullet unseating

[Watch_this71]

I shot Altus' AI classic this weekend. I used my better half's 6mm Creedmoor. It's an Impact action with a Proof prethreaded competition profile barrel. The rifle has maybe 100 rounds through it until Saturday. Hornady 108gr ELD-M ammo was being used. The problem I had through out the match was when I seated a round and time was called, more than once (SEVEN times actually), I would go to clear the rifle and the unfired round would come apart with the bullet stuck in the barrel and the case and unfired powder ejecting from the action. A couple people suggested that the ammo is crappy, another couple more said carbon build up. I've never had a problem with Hornady match ammo before and I run it in my 6.5cm with no problems...

 

[OREGUN]

The bullet is jammed into the lands when you close the bolt. Opening the bolt pulls the bullet. Usually factory ammo has enough “neck tension” that this doesn’t happen. Also, usually factory ammo is seated short enough that the bullet is nowhere near the lands. It’s a lawyer’s nightmare to have a customer call with a complaint that the bullets are jammed into a factory barrel so they tend to seat them on the short end of the scale. In your case, I’m guessing the prefit has a really short throat or is headspaced incorrectly such that the bullet, even at short factory seated length, is much farther forward in the chamber than is normal. It is possible, but unlikely in my opinion, that a lot of carbon build up in the throat could be causing this. Are there any other signs of irregularity? Pressure, hard bolt close, hard open, pierced primers, etc?

 

[Watch_this71]

The bullet is jammed into the lands when you close the bolt. Opening the bolt pulls the bullet. Usually factory ammo has enough “neck tension” that this doesn’t happen. Also, usually factory ammo is seated short enough that the bullet is nowhere near the lands. It’s a lawyer’s nightmare to have a customer call with a complaint that the bullets are jammed into a factory barrel so they tend to seat them on the short end of the scale. In your case, I’m guessing the prefit has a really short throat or is headspaced incorrectly such that the bullet, even at short factory seated length, is much farther forward in the chamber than is normal. It is possible, but unlikely in my opinion, that a lot of carbon build up in the throat could be causing this. Are there any other signs of irregularity? Pressure, hard bolt close, hard open, pierced primers, etc?

I had a couple times where it was hard to close the bolt, yes. As far as pierced primers, no.

 

[JerkyFreak]

Definitely jammed the bullet into the lands. What chamber was cut in the barrel; SAAMI spec or custom chamber?

 

[OREGUN]

Your better half may be trying to blow your face off. Clean the rifle well and then measure the headspace and the “distance to the lands” and the base to ogive length of the loaded ammo you are trying to use. If you don’t know how or have the tools to do that, go to a gunsmith and tell them the story. The fact that you didn’t pierce primers or have hard bolt open is good. The “hard to close” is the camming force of the bolt jamming the bullet into the rifling. That’s not normal in most cases. The fact that it’s happening with factory, ammo means that either something is not right or the gun was designed for hand loads that don’t meet standard dimensions.

 

[Watch_this71]

Definitely jammed the bullet into the lands. What chamber was cut in the barrel; SAAMI spec or custom chamber?

It came precut from Proof, so your guess is as good as mine.

 

[Watch_this71]

Your better half may be trying to blow your face off. Clean the rifle well and then measure the headspace and the “distance to the lands” and the base to ogive length of the loaded ammo you are trying to use. If you don’t know how or have the tools to do that, go to a gunsmith and tell them the story. The fact that you didn’t pierce primers or have hard bolt open is good. The “hard to close” is the camming force of the bolt jamming the bullet into the rifling. That’s not normal in most cases. The fact that it’s happening with factory, ammo means that either something is not right or the gun was designed for hand loads that don’t meet standard dimensions.

Gotcha, thanks

 

[Baron23]

If it is a SAAMI spec chamber, I’d be shocked if factory ammo wasn’t well off the lands.

As for headspace…I defer to those more expert than I but I have a difficult time thinking there could be enough variation to jam a bullet that should be well off the lands.

I’d be very interested in exactly what free bore is in that chamber.

 

[Rob01]

That sounds like a chamber free bore issue more so than an ammo issue. With a SAAMI .183 freebore the factory ammo is about .040” off the lands, if I remember correctly. It’s definitely plenty far enough off to not be jammed into the lands and pull the bullet.

You either have a hell of a carbon ring built up or that change is short in freebore. How has it been cleaned? You know anyone who has an OAL gauge to check freebore?

And how did it perform on the first 100 rounds? Anything similar?

 

[Watch_this71]

And how did it perform on the first 100 rounds? Anything similar?

Not a single problem. BUT... she didn't have to lock and clear with a round in the pipe. So the problem might have been there and we didn't know about it.

 

[Watch_this71]

If it is a SAAMI spec chamber, I’d be shocked if factory ammo wasn’t well off the lands.

As for headspace…I defer to those more expert than I but I have a difficult time thinking there could be enough variation to jam a bullet that should be well off the lands.

I’d be very interested in exactly what free bore is in that chamber.

Calling Altus in a bit about getting it to them.

 

[Watch_this71]

Proof sent me an RMA, I'll follow up when I get word from them.

 

[Tperry]

Also throwing this out there. I've had Hornady 6CM 108eldm ammo that was loaded long from the factory. It would do exactly what you're describing. So it's either a short Freebore or long ammo. I'd be more inclined to expect the ammo is loaded long.

 

[Rob01]

Also throwing this out there. I've had Hornady 6CM 108eldm ammo that was loaded long from the factory. It would do exactly what you're describing. So it's either a short Freebore or long ammo. I'd be more inclined to expect the ammo is loaded long.

How long was it loaded?

 

[Tperry]

It was quite a while ago so I don't remember the numbers. It was longer than any of the other factory ammo. It was the only one that would jam. I'm glad I had only bought a few boxes so it didn't take much to bump them a touch deeper with a seating die.

 

[Rob01]

It was quite a while ago so I don't remember the numbers. It was longer than any of the other factory ammo. It was the only one that would jam. I'm glad I had only bought a few boxes so it didn't take much to bump them a touch deeper with a seating die.

Just wondering as I never heard of it happening or had it happen in thousands of rounds over multiple lots. It wouldn’t take much as the 108 to lands in a SAAMI chamber is only at about 2.825”. I highly doubt that’s his issue and would bet more on a short freebore.

 

[DeathBeforeDismount]

Proof sent me an RMA, I'll follow up when I get word from them.

Proof prefits strike again.

 

[Tperry]

Just wondering as I never heard of it happening or had it happen in thousands of rounds over multiple lots. It wouldn’t take much as the 108 to lands in a SAAMI chamber is only at about 2.825”. I highly doubt that’s his issue and would bet more on a short freebore.

I know @AF_TT had the same issue a few months back with factory 108eldms also. It was just his lot because I had a box of another lot that wouldn't stick. Now that you bring it up I wish we'd measured his ammo.

 

[AF_TT]

I know @AF_TT had the same issue a few months back with factory 108eldms also. It was just his lot because I had a box of another lot that wouldn't stick. Now that you bring it up I wish we'd measured his ammo.

I think I have some I will measure the ogive tonight.

 

[Rob01]

I think I have some I will measure the ogive tonight.

Measure oal to tip also.

 

[OREGUN]

I’ve shot several thousand (probably 4000) Horndy 6CM 108eldm usually purchased in lots of 200-400. I’ve never noticed any seated long but then I’m not measuring it either. Probably have a couple hundred on the shelf. I could measure one or two if it informs the discussion at all.

My bet is on a short throat.

 

[BenE]

In a 6CM proof, my money is on a carbon ring with a near-to-spec or undersized free bore diameter. This can easily happen with an over-used worn reamer. Clean the carbon ring and see if the bullets will still stick.

Edit - with only 100 round on the barrel…. Was it ever cleaned before the match?

 

[Watch_this71]

Edit - with only 100 round on the barrel…. Was it ever cleaned before the match?

It was.

 

[BenE]

It was.

That hurts my odds but still give it a good cleaning and see if they still stick

 

[4O6shootist]

I had a proof prefit 6cm, whole chamber was undersized. Cleaned it very well, and hand reamed with a jgs saami reamer and all was well. Proof makes a decent prefit when a reamer is new, but I think they run them for way too long.

 

[Abey669]

Had this exact same thing happen with a savage rifle a couple of years back. I was running the hornady 103eldx. Also a 6 creed. Wrote it off as a pos rifle and sold it. Had a local gunsmith run a reamer in it and it seemed to fix the issue, but it pissed me off and I wanted nothing more to do with it.

 

[Watch_this71]

Had this exact same thing happen with a savage rifle a couple of years back. I was running the hornady 103eldx. Also a 6 creed. Wrote it off as a pos rifle and sold it. Had a local gunsmith run a reamer in it and it seemed to fix the issue, but it pissed me off and I wanted nothing more to do with it.

That was my 1st gen Bergara. Never went back...