Brass remains in chamber, bolt locks back. Am I over gassed?
- Thread starter Jason3270
- Start date
I'm not sure what they are supposed to look like but the look and feel fine to me.
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It's really difficult to extract the fired round that's left in the chamber. I can move the extractor with a finger but it isn't moving easy, it's pretty tight
Unfired, meaning manually? Yes.
Have you tried any other brands of ammo? That's where I would start. Hornady, federal, honestly any major brand. S&B isn't super great quality, so could be the problem
Is this a new build?
What was your process set your gas block?
What buffer weight?
Did that fired case roll around on the concrete or did it look that rough going in?
What was your process set your gas block?
What buffer weight?
Did that fired case roll around on the concrete or did it look that rough going in?
95% likelihood of being overgassed. Reduce gas via your AGB. If you have the detent version of the Odin AGB, start by reducing gas from the setting you have it on now by 4 or 5 clicks. You want to close gas until the point where on more click fails to lock the bolt back in an empty mag. Do this one round at a time. Once you get lock back, load a full magazine. If it won't cycle from a full magazine, open 1 click.
Edit - on my phone but the primer looks a tiny bit flat in some of the pics. Pics loading slightly blurry though.
Edit - on my phone but the primer looks a tiny bit flat in some of the pics. Pics loading slightly blurry though.
This sounds like a tight chamber. By all means, check gas issues before replacing the barrel or having it reamed again but I’d bet some money it’s your chamber.
S&B ammo tends to be a bit hot. I've never seen a fired case that didn't have a flattened primer
I've had this happen on two brand new barrels. Both had tight chambers that required 2 seconds of turning a reamer by hand to get them perfect. I've had it happen on well used barrels/bolts, but it was relatively easy to get the case out running the charging handle after firing. Once this was caused by a weak extractor spring, once by a worn extractor.
I don't have any reamers, so I had a gunsmith do it. After watching him and getting an explanation of his process I'm pretty confident I could do it. This was on a bare stainless barrel, I had a different smith do a nitrided barrel and he needed a lathe and carbide reamer to do it.
I'm confident that I would have considered that, if i knew what that was. That's a definite negativo on that one. AR10 rookie here. Those AR15s we're so easy to build, and everything worked perfectly. I figured how much more complicated could an AR10 be?
I'm learning, the hard way. I mean, it's a beautiful rifle, and it fires that one shot like a dream, then the wheels fall off the bus, and it becomes a worthless paperweight.
Which is awesome, if you're into paperweights.
In it's defense, that paper isn't going anywhere.
Headspace is measured from the base to the datum line on the shoulder of the cartridge case, i.e., your chamber is formed by a reamer cutting these dimensions. There's probably a wikipedia article that can explain it better than me.
9 times out of 10 you can put together a gun without using the gauges which is a "go", "no-go" and "field". The gauges look like a cartridge or at least a piece of brass.
In your case since it looks like there might be something wrong with the chamber or how the bolt works with it, I'd probably order a go gauge from Midway, Brownells, somebody. It's easier to explain on a bolt action rifle. You put the go gauge into the chamber and the bolt should close easily. It shouldn't close on the no go, but might. It definitely shouldn't close on a field.
If your bolt doesn't close easily on the go it might be short chambered in which case, then you'd need to have somebody give a couple turns of a reamer as Tony suggested. I would remove the extractor to check this if you buy a gauge. I think I've read that with the AR15 it shouldn't take more than 16 lb. of pressure to close on a go gauge.
When I've done it with the extractor in place you can feel it snapping over it and it never even gets close to closing on the no-go. .308 ARs sometimes get cut with a 7.62x51 chamber which is larger so it might close on a .308 no-go but not on the field.
Wilson makes good stuff but I'm not sure whose bolt they use to check headspace. So without a gauge it's impossible to tell if it will really work with your bolt.
If you gun is over gassed it's trying to open the action while the brass is still obturated to the chamber walls and might not extract. But since it does lock back I'm not certain I'd say that's it.
Hope you get it sorted out. Troubleshooting with ammo isn't cheap these days. At least if you buy some tools you have them for future builds.
Thanks, this was really informative (I knew exactly none of this). Going shopping tonight.
If you have calipers (0.001" resolution min), you can measure various parts of the empty brass (body above the web, body below the shoulder, case neck mouth diameter, case neck diameter, case length) to get an idea of what the chamber looks like while you wait for other tools to come in.
Before you start spending money try closing off the gas block as suggested up thread.
I bet there’s a bur in the bolt carrier. I had a similar issue before and that was the issue.
Remove the BCG from the upper and see if loaded and fired cases can be put in and removed without much force. If the rounds are getting stuck in the chamber, that could be part of it. If you can insert the casing into the chamber and a light tap removes it, then chamber a round and see if you can remove it with BCG installed.
If it’s difficult to remove, the carrier is the culprit. I had a JP carrier that had to be replaced. The JP tech himself said there was a bur, so it’s not me making it up. JP just sent me a new carrier.
Remove the BCG from the upper and see if loaded and fired cases can be put in and removed without much force. If the rounds are getting stuck in the chamber, that could be part of it. If you can insert the casing into the chamber and a light tap removes it, then chamber a round and see if you can remove it with BCG installed.
If it’s difficult to remove, the carrier is the culprit. I had a JP carrier that had to be replaced. The JP tech himself said there was a bur, so it’s not me making it up. JP just sent me a new carrier.
S&B brass is also much harder or more brittle than other brass. I don't think they anneal properly. Also the primer hole tends to be a little more shallow and the diameter is tighter if you dont use their primers. I throw all of it in the scrap bucket
Follow up:
So I dropped a round in the barrel and couldn't manually eject it. Kept at it and eventually the bcg pulled the brass apart from the round, which remained lodged in the barrel... gun powder everywhere. At that point I called Wilson Combat to discuss solutions and they had a couple interesting things to say:
1) The round staying lodged in the barrel upon manual ejection is common and normal, if not outright predictable. They said the barrel has very tight tolerances, and this came as no surprise.
2) They headspace barrels only to their BCG, and buying their BCG (.308) will likely resolve the issue. Any other BCG will be a crap shoot.
So it appears I'm neither under or over gassed, not anything else at the moment other than mismatched.
Anyone want to buy a barely used toolcraft 6.5 CM BCG?
Did you mean the bullet stayed in the barrel?
If so that’s a really short throat for a gas gun. I’d say it might be typical with a tight chamber/short throated bolt gun and hand loads but a gas gun shooting factory ammo shouldn’t be in the lands at mag length.
If so that’s a really short throat for a gas gun. I’d say it might be typical with a tight chamber/short throated bolt gun and hand loads but a gas gun shooting factory ammo shouldn’t be in the lands at mag length.
Not sure if it's mentioned, but disassemble the bolt completely when checking HS.
Remove the bolt from the carrier, remove the ejectors and the extractor. You can try it with the extractor in afterwards if you want.
If you aren't comfortable removing the barrel to do this then put a piece of tubing on the tail of the bolt to extend it out where it's reachable. The bolt should close easily on the "GO" gage but not the "NoGo" Do not force anything!
Remove the bolt from the carrier, remove the ejectors and the extractor. You can try it with the extractor in afterwards if you want.
If you aren't comfortable removing the barrel to do this then put a piece of tubing on the tail of the bolt to extend it out where it's reachable. The bolt should close easily on the "GO" gage but not the "NoGo" Do not force anything!
It could headspace properly and still end up having a short freebore and you'd get a bullet jammed up in the lands way too early.
No standards for ar 10 ?
I've swapped ar 15 parts to hell and back. Over the years one bolt was out of speck but functioned.
( 0.002 thousands too tight)
So now we put bench rest barrels in our ar ?
WTF
I've swapped ar 15 parts to hell and back. Over the years one bolt was out of speck but functioned.
( 0.002 thousands too tight)
So now we put bench rest barrels in our ar ?
WTF
Had I known this issue would arise, I would've happily built a bolt action. But alas I had no idea. The gun is built, so if the right BCG will get it running well, then that seems to be the wise move. I'm familiar with the AR platform, so I built an AR thinking it would point shoot and go bang with consistency and accuracy I'm open to suggestions.
I am not judging any particular brand. I prefer things that work without proprietary constraints.
Possibly the chamber is so tight that it needs a (looser bolt) ?
And on the other hand tool craft bcg being Daniel Defense (complient) ?
Proprietary non interchangeable parts on an ar suck, like being held hostage.
I like the term mil spec, it implies parts will match / swap to a reasonable degree.
Possibly the chamber is so tight that it needs a (looser bolt) ?
And on the other hand tool craft bcg being Daniel Defense (complient) ?
Proprietary non interchangeable parts on an ar suck, like being held hostage.
I like the term mil spec, it implies parts will match / swap to a reasonable degree.
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