Anyone else have this issues with their kit? So I was completely siked when I got my lefty 22 conversion kit from my dealer couple of days ago and after about 800 flawless rounds through it, I had a serious issue. I took out my kit to clean it and the receiver plate assembly had cracked when I took it out of my rifle! The part of the conversion that sits up against the buffer and spring had cracked and the kit fell apart. I noticed that the back of the kit had a seam that was welded(the plate that sits up against the buffer and spring had been welded to the rest of the kit). I’m kinda pissed as this kit has been running flawlessly and now my H buffer has some small damage on the face and my kit is useless. I have contacted CMMG and am awaiting a response. Pics included below. I am in no way complaining/bashing on cmmg, i am very pleased with this kit and will get another one regardless. Just seeing if this is a common issue when it comes to this kind of issue or if this is an isolated incident.
Right, I was referring to below the weld area, it doesn’t look like a factory cut…
I only ask because on my CMMG, the back plate is completely round and not flat on the bottom, the area on the piece lined up with the edge on your glass table is what I referring to.
I may just have an older model tho…
Nope just got mine a few days ago , only have about 100 rounds on it Now I’ll be watching that area for cracks! You say it broke right at the weld? CMMG says life time warrenty so that should be covered!
Yeah, on the backplate, if there is a weld, keep an eye one it. I think that I got one of the older kits that was welded together. The newer ones are a solid piece of steel. I got ahold of Stag Arms where I got the kit from and they just sent me a new one out right as I was talking with them. Stag Arms has just earned a customer for life. So pleased, they just had me give the broken kit to my dealer and he will send it out when I get the new one in
Same exact thing happened to me probably around 3000 rounds. I contacted CMMG and they shipped a new one out immediately. I was able to easily epoxy the old one back together. Since it rests against the buffer and is locked in by the back of the receiver, it will function just fine with the crack. It only becomes an issue when you take it apart. I’m still running my old part.
I am planning on trying to find a heavier recoil spring (I think it is the same as a 10-22 spring but not 100% sure) to do away with the unit sometimes failing to go all the way into battery. This might also be a way to prevent the end plate from cracking off.
The weld failed. First I’ve seen but a weld can fail.
If the bolt is not going fully into battery, it’s either dragging too much on the hammer or bolt catch. You can file a 45 degree angle on the rear, bottom lug to help. If it’s the bolt catch, a little off the top of the bolt catch will fix it.
A stronger spring is not necessary.
Dave N
The failure to go into battery is just recent (last 500 rounds or so). I have made the 45 cut on the bolt and have filed away the existing bolt catch, it is still happening. I’m thinking maybe the spring is worn out at 4000 rounds.
Are you using the BHOA? Also, is this an older unit?
The Evolution kits I have been testing, one with over 12K on it, still functions like it did from day one.
I do not have experience with the older kits. But the Evolution kits have been outstanding for me.
Yes, and older dedicated upper. Problems started about the time I installed the Bold Hold Open Device but for the life of me, I can’t find any other part where it is catching. I figure a stronger spring might be an easy fix.
The adjustment screw on the BHOA needs to be all the way down to start. I install the BHOA, turn the rifle to where I can look into the mag well. Insert the allen wrench into the hex screw on the BHOA. While moving the bolt back anf forth, turn the screw clockwise. You will reach a point where the bolt starts to drag. This is also the point where the bolt will not close all the way. Back the screw out 1/2 turn. Operate the bolt. if there is no drag, you should be good.
The biggest problem I have run into with the BHOA is spring tension from the bolt catch spring. The mag spring is not able to overcome the BC spring on 3 out of 5 of my lowers.
I cut 1.5 coils off the BC spring. The bolt locks back every time now, and it has caused no malfunction with my 5.56.
Another thing to look for is if the BHOA is tight when the upper is closed. Symptoms would be when the upper is opened up, the BHOA is squeezed into it.
Sand the frame of the BHOA so it does not stick in the upper. This will cause it to malfunction.
Dave
All that has been done, the BHO frame has been sanded, the set screw has been set, etc. I will look at it again and tinker with it to see if there is something I’m missing.
Yeah, i called to confirm it was one of the older kits and the new one im getting is the piece is one cnc piece of steel. Cant wait and hope it functions just as kick ass as the first. Damn thing ate everything.
CMMG is sending me a replacement, but I figured I’d try and repair my cracked one for use as a back-up.
Here’s the weld area ground down to see the extent of the crack…
