Rounds not chambering

[Darkside-Six]

Ok, so this has got me a little perplexed. Received my new 6GT barrel yesterday. Loaded up some rounds to heat out and zero today and many of them wouldn’t chamber unless forced very hard.

the brass is from my last GT barrel. It’s been full length sized and before I loaded the ammo I verified that they would chamber and they did no problem. It appears that somehow after I throw powder and seat billet they won’t chamber.

I’ve verified several times where my lands are (1.882) and bunkers were loaded to 60 thou off at 1.822. Literally every round is doing this. I verify that the resized piece of brass with fully chamber. I drop powder and seat bullet and the bolt won’t cam over. I have to basically put some heavy force. Once it does then that would will chamber every time. At first I suspected maybe the base was too big but I’d think that if that was the case the brass itself wouldn’t chamber. If bumped shoulders back another 3 thou on some, I’ve seated the bullet down to 1.800 for additional 20 thou even further and still won’t chamber. Ran a scope down in the chamber and everything looks fine. Now grooves or anything else. My first though is it’s something with the brass but even after I force them in I don’t really see any marks. I’ve measured everything before and after to see if something changed but nothing. And unfortunately I don’t have any new pieces of brass to use it against. It’s driving me nuts. Any ideas or help would be very appreciated.

 

[KnowNothing256]

Perhaps the neck of the chamber is too tight? That would explain why resized brass fits but loaded rounds don’t, the neck OD of the round will grow by whatever value you have for your neck tension.

There may be other explanations, but that would do it.

 

[iceng]

If possible, get your 'smith to measure the neck on the reamer, then you measure the diameter of the neck of a loaded round.

Also check your neck mouth chamfer. A tiny burr can upset things, which is why we chamfer cases.

 

[Darkside-Six]

If possible, get your 'smith to measure the neck on the reamer, then you measure the diameter of the neck of a loaded round.

Also check your neck mouth chamfer. A tiny burr can upset things, which is why we chamfer cases.

Spoke with him for about 30 min today and he’s just as confused. Verified all kinds of measurements. Same reamer he uses for his and has no issues. Are loads are almost identical. We both kept coming back to the brass being fired in a different rifle but that doesn’t explain why it will chamber the empty piece of brass but not the loaded round. I fired about 35 rounds today. Took 2 of the pieces that were just fired and reloaded then and they chamber fine.

I also chamfer and deburr every time so not sure that’s it.

 

[918v]

Where on the case is it binding? Paint it with a sharpee and see

 

[2aBaC̶a̶]

Color a round with black sharpie and then gently try to chamber it a few times. You should see wear marks where its jamming.

 

[KnowNothing256]

Two questions:

1) Are your primers at or below flush? If they’re sitting proud of the case head, this would also do it, as your headspace would be artificially increased until you seat the primer flush using force on the bolt. This also wouldn’t show up on fired brass from the new barrel since fire-forming will press it flush.

2) Do your fired necks from this new barrel let you freely push a bullet into them by hand?

 

[spife7980]

Seat the bullet all the way into the neck and see. If the bullet can’t touch the lands but still expands the neck that’s a clue.

bullet puller helps with these experiments

 

[Ironman308]

Try measuring the brass along the body of the case. I have heard of issues when brass is fired in another rifle that the bottom of the body being a clearance issue. Once fired it will form to the new chamber.

 

[Darkside-Six]

Two questions:

1) Are your primers at or below flush? If they’re sitting proud of the case head, this would also do it, as your headspace would be artificially increased until you seat the primer flush using force on the bolt. This also wouldn’t show up on fired brass from the new barrel since fire-forming will press it flush.

2) Do your fired necks from this new barrel let you freely push a bullet into them by hand?

Yes primers are below flush. No I cannot freely push round o to fired necks.

 

[Darkside-Six]

Seat the bullet all the way into the neck and see. If the bullet can’t touch the lands but still expands the neck that’s a clue.

bullet puller helps with these experiments

Tried that. Still wouldn’t chamber.

 

[spife7980]

Tried that. Still wouldn’t chamber.

I’d assume it’s gotta be neck diameter. The diameter and lengths measurements of everything before and after

 

[Darkside-Six]

Colored a few rounds. Seems to be the base. I measured that compared to what my friend said the base of a virgin case is. Problem is when I measure the base of a facade that I just fired in this barrel today it measures the same. .

 

[Texasflyer]

Will it chamber a factory round?

 

[Tokay444]

Yes primers are below flush. No I cannot freely push round o to fired necks.

If you can't push a bullet into a fired case, you don't have enough neck clearance.
Hope you have a lathe.

 

[Darkside-Six]

Will it chamber a factory round?

Don’t know. Don’t have factory rounds or virgin brass

 

[KnowNothing256]

If you can't push a bullet into a fired case, you don't have enough neck clearance.
Hope you have a lathe.

Yep, that’s it, insufficient neck clearance in the chamber.

 

[Darkside-Six]

If you can't push a bullet into a fired case, you don't have enough neck clearance.
Hope you have a lathe.

No. I don’t have a lath. I didn’t try a whole lot of pressure but I tried pushing it in a fired case by hand and didn’t really go. As I said, I took 5 rounds that were fired today, resized then and loaded then and had no issues. It’s obviously something with my brass. I just can’t figure why an empty case will chamber fine (which should rule out base and shoulder) but a loaded round will not. I verified my neck diameter with the smith who cut it. He shoots with me regularly. Same dimensions as his loaded rounds and his work fine in his chamber. (Same reamer).
Once a force the bolt to close.......which sometimes takes more pressure than I’d like, that round will then chamber. So it looks like I’ll be doing this about 400 more times and then should be fine

 

[stello1001]

Can we get the darn picture already of your entire case painted with sharpie. We want to see where it binds.

 

[KnowNothing256]

Can we get the darn picture already of your entire case painted with sharpie. We want to see where it binds.

We know where it binds, at the neck. That’s the only dimension that changes when you load up the ammo vs resized+primed brass. Plus, OP verified that he can’t hand-push a bullet into a fired neck, which he should be able to do no problem.

It’s a too-tight chamber neck.

 

[Darkside-Six]

We know where it binds, at the neck. That’s the only dimension that changes when you load up the ammo vs resized+primed brass. Plus, OP verified that he can’t hand-push a bullet into a fired neck, which he should be able to do no problem.

It’s a too-tight chamber neck.

No. I just tried again and can push a billet into them. Guess I didn’t really try hard enough last time. I’ll attach a picture of the painted round below. As menstioned above it seems like it’s rubbing along the base but that still doesn’t explain why a empty round chambers and a loaded one doesn’t.

 

[Darkside-Six]

 

[KnowNothing256]

Am I right in seeing that there’s a little lip poking out at the neck rim? You’d be able to feel it snag a fingernail if it’s really there

 

[Tchitcherine]

Are you chamfering & deburring your case mouths?

 

[2aBaC̶a̶]

Wow, debur and chamfer much? I would say something is peening your case mouth. Maybe even your seating die.

 

[eschafer]

verify your chambers' trim length... is brass requiring a trim?

 

[TheOfficeT-Rex]

Doesn't look like a chamfer issue - The case looks too long for the chamber, the neck is hitting the end of the chamber and squishing back. Try trimming one shorter.

 

[Tchitcherine]

If the mouth looks nice and chamfered before attempt to chamber, then yeah, trim length.
If it's already mangled before attempt to chamber, then something earlier in the process.

 

[Darkside-Six]

Wow, debur and chamfer much? I would say something is peening your case mouth. Maybe even your seating die.

right is a prepped case. Chamfered and deburred. Left is one just fired in it today.
Probably some of the marker your seeing. I always chamfer and debur

 

[Darkside-Six]

Doesn't look like a chamfer issue - The case looks too long for the chamber, the neck is hitting the end of the chamber and squishing back. Try trimming one shorter.

If that’s the case wouldn’t it NOT chamber on an empty case?
These do chamber when cars is empty. Only after loading billet do they not chamber.

 

[KnowNothing256]

If that’s the case wouldn’t it NOT chamber on an empty case?
These do chamber when cars is empty. Only after loading billet do they not chamber.

It might chamber a just-barely-too-long case with no bullet as the throat forces the lip of the case inward. If there’s a bullet there, I could envision the case mouth brass having nowhere to go.

 

[Tokay444]

When empty it’s easier for the mouth to collapse. Much harder when there’s a projectile in the way.
There is most definitely a prominent burr around the mouth of that markered case.

 

[Mauser06]

You shouldn't have to push to hard for a bullet to go into a case mouth fired from that chamber. You may have to neck turn.

What do your loaded rounds measure at the neck? What are the specs of the reamer?



The sharpie pic....there is clearly something going on to the mouth if that case was nice when it started. I agree that it looks like it's probably too long.

Do you have a bore scope to check out the chamber?

Try trimming a case that won't go and see if it goes. Even if you gotta trash a case and take it below spec. I'd go down in increments and see if/when it's short enough to go.

 

[Tokay444]

What do the case lengths measure?

 

[Darkside-Six]

Ok. So I just trimmed them down quite a bit and had no issues. So it seems like that is what is causing it.
The trim length for 6GT is supposed to be 1.720 according to George but even virgin Hornady cases are inky 1.716-1.717. So that is what I’ve been trimming too. I just trimmed down to 1.70 and they closed like butter so that seems to be the culprit. Now I need to adjust my trimmer a little better so they’re not so far and go from there.
Much appreciated fellas!

 

[Simonsza1]

That’s the worst looking case mouth I’ve ever seen for one that’s supposedly been prepped.

 

[Tchitcherine]

FWIW, there's this

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[Brux]

No you need to have your throat fixed in your barrel

 

[Mauser06]

No you need to have your throat fixed in your barrel

I was wondering if jamming and shooting rounds could have damaged the chamber or throat....I don't know enough to answer that one. Can't imagine it was good for it.

 

[Darkside-Six]

No you need to have your throat fixed in your barrel

I doubt it. Thinking my necks maybe too long from the shoulder The smith who did my barrel also shoots GT and so does a few guys I shoot club matches with. Same reamer for all of them. I’m the only one with an issue and I’m the only one using brass fired in a different chamber. I’d I have to trim them a little shorter for now I can live with that. New brass should be coming any day now apparently

 

[KnowNothing256]

Agreed that it's way easier to just trim an extra 15-20 thou than to re-ream the chamber, with likely no adverse accuracy effects. Go shoot.

 

[supercorndogs]

A chamber should have quite a bit of room for brass, past the maximum trim length. It looks like actual maximum trim length should be a 1.732
for a 6GT chamber.

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[Darkside-Six]

A chamber should have quite a bit of room for brass, past the maximum trim length. It looks like actual maximum trim length should be a 1.732
for a 6GT chamber.

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Yeah you’re correct. Bro g that the brass was fired in a different chamber I doubt it’s the reamer or my new chamber. Tried everything else. Bunking shoulders further back, seating billets deaper.
Trimming fixed it all. I didn’t think I needed to trim originally cause all my cases were on the 1.716 area which is under the trim length advised by GA of 1.720 but I settled on 1.710 and they close no problem now. Will have a little more carbon build up but should t affect anything else. Got rid of the headache.

 

[Tchitcherine]

If room for brass past the case length < 0, for example by loading factory ammo into a chamber shorter than spec, and you force the bolt closed, does that not create a potentially dangerous overpressure condition?

 

[iceng]

Measure brass length, compare to SAAMI length specs.

Something weird is going on with your case mouth, it has a burr.

Get a piece of brass, no primer or projectile. FL size it. Try it in your chamber, close the bolt fully. Put marker on case neck and mouth. I expect the case mouth to be rubbed clean or shiney spot.

You may need to open / close bolt handle 3 or 4 times to get the marker to remove properly.

I have seen this once before. Marginally short chamber with marginally long brass. Not a big deal.

 

[Tokay444]

Measure brass length, compare to SAAMI length specs.

Something weird is going on with your case mouth, it has a burr.

Get a piece of brass, no primer or projectile. FL size it. Try it in your chamber, close the bolt fully. Put marker on case neck and mouth. I expect the case mouth to be rubbed clean or shiney spot.

You may need to open / close bolt handle 3 or 4 times to get the marker to remove properly.

I have seen this once before. Marginally short chamber with marginally long brass. Not a big deal.

Read the whole thread.

 

[iceng]

Literally just read the end result, for some reason I scrolled past it. Glad it's fixed. Cheers for the heads up.