lmt bolt lock problems

AR/M4 AR Technical Discussion
1

Ok i just got a new in box lmt mrp piston rifle with 16in barrel. I installed my ready-mag and phase 5 tactical EBRvs2 from my colt 6920. Went shooting today and all 12 of my GI mags failed to lock back the bolt on the last shot but my 2 P-mags would lock the bolt just fine. I did a search on this sight and on the web seems others have had this problem. Has anybody been able to resolve this problem? I have heard about the weight of the EBR being the issue what gets me is the P-mags work fine and when I maunuly work the bolt it locks back on the GI mags.

btw the other mags ar Bravo company,D&H Industries & the LMT mag.

thanks for any help or suggestions.

2

Are you using magpul followers in the GI mags?
My LMT would not lock the bolt back with the standard GI followers swapped to magpul followers and it fixed all 10 GI mags that I am using.

3

No. I am not they are the standerd green followers. I thought that might help too but I have to order them. I will try that thanks.

4

You are describing the exact problem I had but I don’t run the phase 5 tactical EBRvs2 I would try the magpul followers if that doesn’t fix it then I would remove the phase 5 tactical EBRvs2 and retry it again.

5

My thoughts also. I wish I had brought my Colt with me so I could swap lowers to see if the problem persists. I am leaning towards the followers as the problem with the P-mags working fine.

6

MY bolt wouldnt lcok back when I was running a BAD. Once I removed the BAD the bolt started locking back. I would start with removing the EBR.

7

Did you have the same problem with P-mags?

8

If it is the EBRvs.2 & B.A.D. are the problem. What is the solution? I really want this setup to work.

My thinking is maybe the the spring for the bolt catch might not be strong enough. When swithing the EBR from the Colt to the LMT it did seem like the Colt mag catch spring was stiffer.

I’m not sure if that would be an issue or not.

9

I was running it on a 5.45 upper so I dont know. I do know others had issues with the bad doing the same thing. However my dad runs a BAD and pmags without any issues. Colt lower.

I am going to tweak with my mag catch and springs. I want my bad to work :(.

10

So I went shooting again this time I brought my Colt. I swapped the LMT upper on the colt lower ran fine and bolt locked back.and the colt upper bolt locked back with the lmt lower with the EBR. So I thought mybe it was the buffer lmt has H2 and colt has an H buffer. Swapped buffer and still would not lock back with GI mags.
So I got a hold of a C-Products mag with there magpull knock-off follower and bolt locked back fine.
So I guess I will be buying magpul followers.
Thanks for all the help.

11

youll be solving two problems with that: your lock back and possible follower tilt. I bought some USGI with green followers, first thing I did was buy magpul followers to go with it and change them out. The follower engages the bolt catch to lock back on empty, not sure how much different the greenie is vs the magpul follower with respect to the part of the follower that engages the catch. Maybe the magpul one is a little higher who knows