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Started By
Message
AR question- failure to lock back the bolt- mechanical, not gassing.
Posted on 4/14/23 at 9:52 am
Posted on 4/14/23 at 9:52 am
Curious about what to troubleshoot=
I have recently put together a rifle that shoots fine, but the bolt hold-back seems loose... it doesn't tend to lock the bolt back on last round. That, I understand, usually is a gassing issue, but this isn't the case.
If I cycle the handle dry, with an empty mag, or with no mag and I hold the release down to lock it-
it will catch, but not hold tightly. Sometimes it will hold and then release, and sometimes it will hold, but if I slap the buttstock, the bolt will slam forward.
So, this was built from a stripped lower. What do I need to do and look at? Bolt release and spring? Do I just need a new/better one, or is this something I might be able to reseat?
I have recently put together a rifle that shoots fine, but the bolt hold-back seems loose... it doesn't tend to lock the bolt back on last round. That, I understand, usually is a gassing issue, but this isn't the case.
If I cycle the handle dry, with an empty mag, or with no mag and I hold the release down to lock it-
it will catch, but not hold tightly. Sometimes it will hold and then release, and sometimes it will hold, but if I slap the buttstock, the bolt will slam forward.
So, this was built from a stripped lower. What do I need to do and look at? Bolt release and spring? Do I just need a new/better one, or is this something I might be able to reseat?
5
Posted on 4/14/23 at 10:09 am to Scoob
Did you put the spring and plunger in your bolt catch?
Posted on 4/14/23 at 10:11 am to Scoob
quote:
if I slap the buttstock, the bolt will slam forward.
that will happen with pretty much any "lower tier" AR. my Anderson does that, but my Daniel Defense doesn't.
eta: correction, my DD does do it.
where were your casings ejecting? reference the image below:
This post was edited on 4/14/23 at 10:23 am
Posted on 4/14/23 at 11:14 am to Scoob
quote:
I have recently put together a rifle
Disclaimer; I am Not a Gunsmith. These are just suggestions from a highly unqualified source (me)
Make sure your Buffer Spring isnt too long, which could keep the carrier from being able to slide back far enough to properly clear the catch.
I may sound like a dumbass here, but when I got into assembling, I acquired a few different weight buffers and a pile of different size springs just for such issues.
Posted on 4/14/23 at 11:15 am to Scoob
I wouldn't worry too much about the bolt coming forward when held by the bolt catch with no magazine inserted. At that point, the only thing keeping the bolt catch out of its natural position (i.e. out of the way) is the buffer spring tension on the bolt. It makes sense that if you knock the rear of the stock (compressing the buffer spring), the bolt catch will revert to its natural position and the bolt will slam forward.
What's odd is that it's doing the same thing on an empty mag. When an empty mag is in, the follower should be firmly engaged with the bolt catch tab (see photo below), and the bolt thus shouldn't be able to go into battery.
To me this is likely either a magazine issue or a bolt catch spec issue. Try this:
1. Use a different magazine and do the same test. If the mag you're using has a weak or out of spec follower, it may not be reliably engaging the bolt catch. If that's the case, just ditch that mag.
2. If it's not a magazine issue (i.e. there's not enough surface area on the bolt catch tab to reliably hold onto the follower), you may have an out-of-spec bolt catch that needs replacing.
What's odd is that it's doing the same thing on an empty mag. When an empty mag is in, the follower should be firmly engaged with the bolt catch tab (see photo below), and the bolt thus shouldn't be able to go into battery.
To me this is likely either a magazine issue or a bolt catch spec issue. Try this:
1. Use a different magazine and do the same test. If the mag you're using has a weak or out of spec follower, it may not be reliably engaging the bolt catch. If that's the case, just ditch that mag.
2. If it's not a magazine issue (i.e. there's not enough surface area on the bolt catch tab to reliably hold onto the follower), you may have an out-of-spec bolt catch that needs replacing.
Posted on 4/14/23 at 11:37 am to finchmeister08
quote:Pretty sure I did
Did you put the spring and plunger in your bolt catch?
I might pull that and recheck.
quote:Well, it's a GGP lower, with a Sabre Defence upper. I wouldn't call that a 'lower tier'. And there's zero play between upper and lower.
that will happen with pretty much any "lower tier" AR. my Anderson does that, but my Daniel Defense doesn't.
eta: correction, my DD does do it.
quote:I think gas is fine, sitting around 4 o'clock. And depending on ammo, that could change. But what I'm talking about is doing it manually, with me pulling the charging handle, and either catching the mag or holding the bolt catch down.
where were your casings ejecting? reference the image below:
My first thought was=
I had a Nickel Boron BCG, maybe with it oiled, it was too slick and just wouldn't hold. But I swapped in a spare nitride BCG, and again it wants to slam forward.
Looking online, it seems the areas I want to troubleshoot would be
1 bolt catch lever
2 spring for that
3 buffer spring (might be too stiff, pushing too hard).
It's a carbine with 6 position tube, and the spring is supposed to be a carbine buffer spring. I know I have several of those in other guns that work fine, I guess that would be a quick first check.
I'm otherwise very satisfied with this. It has zero issue feeding, even crappy Tula. And it's accurate enough for my needs.
My son took it to the range to zero the (cheapo) 1-4x24 LPVO, here's what he got at 25 yards, standing:
(ignore the Aluminum Black, we have that in case of any scratches
) 
Posted on 4/14/23 at 11:43 am to TideCPA
quote:I'm starting to lean to #2...
To me this is likely either a magazine issue or a bolt catch spec issue. Try this:
1. Use a different magazine and do the same test. If the mag you're using has a weak or out of spec follower, it may not be reliably engaging the bolt catch. If that's the case, just ditch that mag.
2. If it's not a magazine issue (i.e. there's not enough surface area on the bolt catch tab to reliably hold onto the follower), you may have an out-of-spec bolt catch that needs replacing.
I've tried a few mags, Pmags, steel and aluminum. It's a gun issue, not mag specific.
Posted on 4/14/23 at 12:38 pm to Scoob
Your gun is just dirty. Clean it and see if that fixes the problem. If it doesnt work....come clean mine and see if that works.
Posted on 4/14/23 at 12:38 pm to Scoob
well, damn it
I just tried, and couldn't duplicate it. Not firing, but just taking the gun out of the safe...
pulled the lower off, and looked at that with a magazine. Plenty of material catching the follower.
Spring definitely present, normal tension and resistance.
Reassembled, put the mag back in, pulled the handle. Locked back. Couple of slaps with the mag, no release. Stayed locked back.
Dropped the mag, started slapping the butt. Soft at first, increasing until the last couple stung the heel of my palm... stayed locked back.
Pulled the handle back, and it slammed home tight.
Mag inserted again, locked back. Slapped the frick out of it, stayed locked. Removed the mag, stayed back... a couple firm slaps and it did release.
Mag back in, stays locked, even with slaps.
Mag lock spring tension too low (need a stronger spring)?
I just tried, and couldn't duplicate it. Not firing, but just taking the gun out of the safe...
pulled the lower off, and looked at that with a magazine. Plenty of material catching the follower.
Spring definitely present, normal tension and resistance.
Reassembled, put the mag back in, pulled the handle. Locked back. Couple of slaps with the mag, no release. Stayed locked back.
Dropped the mag, started slapping the butt. Soft at first, increasing until the last couple stung the heel of my palm... stayed locked back.
Pulled the handle back, and it slammed home tight.
Mag inserted again, locked back. Slapped the frick out of it, stayed locked. Removed the mag, stayed back... a couple firm slaps and it did release.
Mag back in, stays locked, even with slaps.
Mag lock spring tension too low (need a stronger spring)?
Posted on 4/14/23 at 12:42 pm to TideHater
quote:Ha, so I get that's probably a joke... but maybe?
Your gun is just dirty. Clean it and see if that fixes the problem.
He did clean the guns afterwards, but where exactly do you clean to address this? In and around the mag catch?
Could maybe too much oil make it too slick?
Edit= not the mag release, the bolt catch.
This post was edited on 4/14/23 at 12:45 pm
Posted on 4/14/23 at 2:31 pm to Scoob
Put a Vitor A5 buffer system on it and see instant improvement.
Posted on 4/14/23 at 9:11 pm to Scoob
Generally you don’t want a lot of CLP, and only want to strategically apply it, but this does not sound like you’re having a CLP problem.
With that said, you’ve lost me regarding your AR. Good luck figuring it out.
I highly recommend going to a local gunsmith. You may be smart enough to figure it out but it sounds like a big ole headache until then.
With that said, you’ve lost me regarding your AR. Good luck figuring it out.
I highly recommend going to a local gunsmith. You may be smart enough to figure it out but it sounds like a big ole headache until then.
Posted on 4/15/23 at 11:43 am to Bosethus68
quote:
Make sure your Buffer Spring isnt too long
I too have had this issue. I received the wrong spring in a large order of parts. Take your buffer spring out and compare it to a spring in a rifle that functions properly.
Posted on 4/15/23 at 7:40 pm to PaperPaintball92
quote:We have a winner= the buffer spring was too long.quote:
Make sure your Buffer Spring isnt too long
I too have had this issue. I received the wrong spring in a large order of parts. Take your buffer spring out and compare it to a spring in a rifle that functions properly.
Now, curious how that will affect ejection, as it was spitting around 4 o'clock with that. Guess we'll see...
so, I'm going to check some other rifles, and see if it's the buffer spring for an A2, or for the AR 10. My guess is the A2... or maybe the A1 kit I had.
Posted on 4/15/23 at 8:45 pm to Scoob
quote:
We have a winner= the buffer spring was too long
Good deal, I assume it’s an easily overlooked part because I fought with a similar issue for a while.
Posted on 4/16/23 at 7:38 am to Scoob
quote:
We have a winner= the buffer spring was too long.
Outdoors board is undefeated.
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