Ar10 bcg not locking all the way back, solution found post #8

[cpl_dan]

the bolt catch isn't catching the face of the ar10 bolt. I dremeled down the bolt catch which helped but still not engaging. I have the correct ar10 buffer not sure on the spring though. What could cause this issue?

[Kmai24]

I had a similar problem like you as well with my Lr308 build. I was runnnig a rifle length gas system with rifle length buffer tube and a JP silent buffer. For some reason the bolt would not clear the bolt catch, even when I pulled the charging handle all the way back. I ended up take a bit of material off on the back end of the bolt catch. I did a little at a time, just enough for the bolt to clear. Works just fine now.

[Kmai24]

I had a similar problem like you as well with my Lr308 build. I was runnnig a rifle length gas system with rifle length buffer tube and a JP silent buffer. For some reason the bolt would not clear the bolt catch, even when I pulled the charging handle all the way back. I ended up take a bit of material off on the back end of the bolt catch. I did a little at a time, just enough for the bolt to clear. Works just fine now.

I would first double check to make sure you got the right spring and buffer combo, check to see nothing is inside the buffer tube to restrict it from going all the way back. If all else fails, you can do what I did.

** sorry didn’t meant to quote myself, replying on my phone and thought I hit the “edit” button.

[kcstott]

the bolt catch isn't catching the face of the ar10 bolt. I dremeled down the bolt catch which helped but still not engaging. I have the correct ar10 buffer not sure on the spring though. What could cause this issue?

How many rounds through the gun?? Has it ever worked right??

[ar15barrels]

the bolt catch isn't catching the face of the ar10 bolt.
I dremeled down the bolt catch which helped but still not engaging.
I have the correct ar10 buffer not sure on the spring though.
What could cause this issue?

1. Upper receiver blocking the bolt catch travel.
Remove the bolt carrier group and reinstall the upper on the lower and check the total amount of bolt stop travel WITHOUT the bolt carrier.
Make note of how much travel the bolt catch has without the bolt carrier in the way and compare that to the travel with the bolt carrier in place.
If there is notably more travel without the bolt carrier in place, your upper/lower/bolt catch are fine.
If the travel is the same, you have a problem with your upper/lower/bolt-catch.

2. Too long of a stock screw.
Remove the stock screw and see if the problem goes away.

3. Buffer spring too long.
Try removing the buffer spring all together, reinstall the buffer and see if the bolt carrier travels farther rearward.
If the spring makes a difference, the spring was wrong.

If the lack of spring does not change anything, you have a buffer tube/screw/carrier mismatch problem or the bolt catch is not clearing the upper receiver.

[baih777]

Do you have rifle length or carbine buffer length tube?

[ar15barrels]

I had a similar problem like you as well with my Lr308 build. I was runnnig a rifle length gas system with rifle length buffer tube and a JP silent buffer. For some reason the bolt would not clear the bolt catch, even when I pulled the charging handle all the way back. I ended up take a bit of material off on the back end of the bolt catch. I did a little at a time, just enough for the bolt to clear. Works just fine now.

The buffer should have an extra 3/16" to 1/4" of travel BEHIND the engaged bolt catch.
This is the length that you need for the magazine's follower to get the bolt catch to pop up while the gun is cycling.
If you have too little over-travel, the bolt will ride over the bolt catch before the magazine can get the bolt catch in front of it.
If you have too much over-travel, the bolt carrier gets going faster and hits the bolt catch with a lot more energy and will eventually break the catch or damage the receiver.

[cpl_dan]

its a never fired build, currently using an ar15 carbine length buffer tube. I read in another forum that you can place a small dot of grease at end of buffer and pull charging handle back and see if it bottoms at the end of the buffer tube if it doesn't then issue could be "spring binding" as they said. So I purchased another ar10 carbine buffer spring and is now working properly. It could have been a bad spring I guess?




for anyone running into this issue my suggestion is check the following:

1) correct 308 buffer not ar15
2) correct size ar10 buffer spring , rifle/carbine
3) check bolt catch is not hitting upper receiver, if so grind some material off the bolt catch not the stripped upper.

[kcstott]

its a never fired build, currently using an ar15 carbine length buffer tube. I read in another forum that you can place a small dot of grease at end of buffer and pull charging handle back and see if it bottoms at the end of the buffer tube if it doesn't then issue could be "spring binding" as they said. So I purchased another ar10 carbine buffer spring and is now working properly. It could have been a bad spring I guess?




for anyone running into this issue my suggestion is check the following:

1) correct 308 buffer not ar15
2) correct size ar10 buffer spring , rifle/carbine
3) check bolt catch is not hitting upper receiver, if so grind some material off the bolt catch not the stripped upper.

You never said if the original buffer was a carbine buffer or not.

Bad spring. another guess that is so far off the mark.

Lets see you bought a carbine buffer and it worked, I wonder why???

[Sailormilan2]

I had a similar problem with my PA10 build. I used a no name spring, which would not allow the bolt carrier to lock back. It turns out that while the spring was the proper length, it had too many coils, and couldn't compress to the proper length. Changing the spring fixed the problem.