AR-10 Bolt head issue

[Winkfish]

I spent a little time digging into the lower last night. The bolt catch is from Aero as well, it does have the correct spring in there. What I did find interesting is that the hammer when fired or in the vertical position does press against the bolt catch as shown in the picture. I took a look at a DPMS lower I had with a Timney trigger in it and it does not touch the bolt catch.


With the hammer back the bolt catch moves freely and operates as one would expect. Manipulating the lower alone with the upper removed, and the hammer up the bolt catch does stick and not move freely. One would not think this would be an issue as this is not a normal position during the firing and locking back of the bolt, so I am going to ignore that.


I have fully disassembled the bolt carrier, lubed it all up and I will get it back out to the range here soon. I am starting to wonder if part of the problem is user error and that the system really has only 100 rounds through it and it need a little more break in time. There does not appear to be any uneven wear on any of the components at this time.

 

[Darryle]

Most do that, especially drop in triggers, my CMC and TT both do.

That is not the issue, hammer is down when the bolt is back anyhow.

Look at the sides of the bolt catch for shiny spots

 

[Darryle]

Your previous picture shows the hammer down for reference

 

[cohunt]

Couple other things

So there are no issues when firing-- just when hand cycling-- right?

The mag follower pushes up on the bolt catch when empty-- what mags have you tried? Have you tried more than 1 brand?

Are you sure the buffer and spring are for dpms/lr308 compatible receiver sets and not ar-10 sets?

What charging handle are you using?

 

[rpol98]

Good Morning to all your AR-10 folks.

My buddy just got a new AR-10 and we were shooting it this weekend and noticed that the bolt head was staying forward in some instances and then when the bolt locked back on the last round it was in the forward position. So when he would insert a new magazine it would fail to feed correctly.
...

All the ammo has been the same factory Hornady 147gr ELDM.
The gun runs the ammo well, and yes there is a supurlative arms gas block.

so you're not getting Last-Round-Bolt-Hold-Open, i.e. when you shot the last round in the mag, and the bolt didn't lock back on empty (bolt face behind the bolt catch).

also, you have an adjustable gas block. sounds like you need to open it up a click or two.

now that you've ruled out mechanical incompatibilities.

 

[ARlife4me]

Does/did the bolt catch have the spring or pin missing? I have several AP's I've built myself and 1 had the wrong bolt catch in it. My mistake on it being 1 for an ar15 and it caused issues like you're having. It would bind up between the bc and the back of the bolt.

 

[Winkfish]

Based on what I am tried over the weekend it appears you really need to be deliberate about pushing the bolt catch button. If you don't really press it into the frame it will not travel up far enough to catch it correctly.

It is catching it just fine on last round lock back so I am thinking that most of his problems are related to how he is manipulating the rifle.

I will have to see if there are any other bolt catches out there that may have a larger paddle or are a little more offset to make it easier to operate.

 

[rpol98]

earlier versions of Aero M5 bolt catch had a straight-sided lower half, current versions of the Aero M5 bolt catch now have a raised "button" with serrations that make it easier to depress. If your friend has the earlier version, then swapping out to the newer version is the easy fix.

early version:

current version:

 

[itchytriggerfinger]

Have you considered putting a BAD lever on? I have one on every AR platform I've built. I would not build one without it.
The best thing about the BAD lever is it can be manipulated from either side of the gun.

 

[Darryle]

Have you considered putting a BAD lever on? I have one on every AR platform I've built. I would not build one without it.
The best thing about the BAD lever is it can be manipulated from either side of the gun.View attachment 394941

How does that solve his issue?

 

[itchytriggerfinger]

How does that solve his issue?

In response to the OP post #21

 

[ARlife4me]

Have you considered putting a BAD lever on? I have one on every AR platform I've built. I would not build one without it.
The best thing about the BAD lever is it can be manipulated from either side of the gun.View attachment 394941

That's a phase5 ambi bolt release, not a BAD lever (which is an ambi also).

 

[Darryle]

I'd be willing to bet that an ambi-bolt release won't correct the issue.

If the owner is having trouble manipulating a common Mil-Spec style bolt release, an ambi will make the situation worse. The owner simply needs time behind the trigger, and a lot of it.

 

[ARlife4me]

I'd be willing to bet that an ambi-bolt release won't correct the issue.

If the owner is having trouble manipulating a common Mil-Spec style bolt release, an ambi will make the situation worse. The owner simply needs time behind the trigger, and a lot of it.

I'm still not sure what the problem is? Is the catch not all the way down so the bcg doesn't ride against the catch causing it to bounce and holding it between the bolt and the carrier? Is the catch machined incorrectly so it doesn't move freely? I might be missing something?