At first I thought it might be the tight tolerances in the Larue Stealth Upper and the carrier, but that combo works just fine with a different lower that has a VLTOR stock. I Also tried the LBNM carrier in a a different upper (CMT) with that stock and it had problems. That CMT upper with an LMT carrier works fine with the PRS.

I then took the stock off and just left the buffer tube thinking that maybe the stock was binding the tube in a strange position, but the problem was still there. So it seems to be the combination of the LBNM carrier and the Buffer Tube I have for my Magpul PRS.



So here's what happens;

Pull the CH back and the carrier sticks in the buffer tube. It takes a lot of smacking to get it unstuck.

Anybody else have this problem?

I run a YNM with a VLTOR upper with a PRS with no problems of the such, have you shined a light down the extension to see where it is exactly rubbing/sticking?

ill have to try to put my y/m carrier in my 6.8 with the prs stock on it when i get home and ill see what mine does.  i had some tolerence issues with my y/m carrier and my stealth upper but after 300rds its smooth as hell.

Quoted: I run a YNM with a VLTOR upper with a PRS with no problems of the such, have you shined a light down the extension to see where it is exactly rubbing/sticking?

Yeah, there aren't any specific marks that are helpful.

Quoted: ill have to try to put my y/m carrier in my 6.8 with the prs stock on it when i get home and ill see what mine does.  i had some tolerence issues with my y/m carrier and my stealth upper but after 300rds its smooth as hell.

I thought at first it was the Stealth + LBNM tight tolerances causing the problem. but when I put a CMT upper on the lower with the LBNM I had the same problem.

So out of all the combinations of lowers, uppers, stock, and carriers, the only 2 things that where present when it sticks are the LBNM carrier and the buffer tube that I have for my PRS.

I guess I try to buy a new A1 buffer tube and see if it fixes anything.

Just thought of something else that was there every time it sticks. The RRA 2 stage trigger. I was just told that another friend had trouble with his RRA binding the bolt in his 6.8.

Quoted: At first I thought it might be the tight tolerances in the Larue Stealth Upper and the carrier, but that combo works just fine with a different lower that has a VLTOR stock. I Also tried the LBNM carrier in a a different upper (CMT) with that stock and it had problems. That CMT upper with an LMT carrier works fine with the PRS. I then took the stock off and just left the buffer tube thinking that maybe the stock was binding the tube in a strange position, but the problem was still there. So it seems to be the combination of the LBNM carrier and the Buffer Tube I have for my Magpul PRS. So here's what happens; Pull the CH back and the carrier sticks in the buffer tube. It takes a lot of smacking to get it unstuck. Anybody else have this problem?

If I am reading your post correctly, the problem only occurs with your one particular lower receiver/buffer tube.  On rare occaision, I have seen lower receivers where the threads for the buffer tube (receiver extension) have not been cut perfectly true to the bore.  This results in the the buffer tube (any buffer tube) sitting at a very slight angle to the bore of the upper receiver when installed on this lower receiver with the problem threads.  

When the bolt carrier reaches a certain point in its rearward travel where roughly half of it is in the buffer tube and half remains in the upper receiver, it can bind.  If the same bolt carrier and stock set-up work properly when installed on a different lower receiver, the odds are this is your problem.

Quoted: Quoted: At first I thought it might be the tight tolerances in the Larue Stealth Upper and the carrier, but that combo works just fine with a different lower that has a VLTOR stock. I Also tried the LBNM carrier in a a different upper (CMT) with that stock and it had problems. That CMT upper with an LMT carrier works fine with the PRS. I then took the stock off and just left the buffer tube thinking that maybe the stock was binding the tube in a strange position, but the problem was still there. So it seems to be the combination of the LBNM carrier and the Buffer Tube I have for my Magpul PRS. So here's what happens; Pull the CH back and the carrier sticks in the buffer tube. It takes a lot of smacking to get it unstuck. Anybody else have this problem? If I am reading your post correctly, the problem only occurs with your one particular lower receiver/buffer tube.  On rare occaision, I have seen lower receivers where the threads for the buffer tube (receiver extension) have not been cut perfectly true to the bore.  This results in the the buffer tube (any buffer tube) sitting at a very slight angle to the bore of the upper receiver when installed on this lower receiver with the problem threads.   When the bolt carrier reaches a certain point in its rearward travel where roughly half of it is in the buffer tube and half remains in the upper receiver, it can bind.  If the same bolt carrier and stock set-up work properly when installed on a different lower receiver, the odds are this is your problem.

Yup, that's pretty much it, but I should note that I have 2 uppers I use on that lower, a precision 6.5 grendel with the Stealth Upper + LBNM carrier and a precision 223 with a CMT upper and LMT carrier.

The 223 upper works fine on that lower unless I swap the carriers, then the 223 upper doesn't work and the Grendel upper does. So it seems the tighter tolerences of the LBNM carrier amplify the problem.

Fixed it.

I just swapped lowers with my back-up carbine, everything works fine on both rifles.

Thanks guys.