So a while back I decided to buy a 9mm carbine. I looked at models like the CX4, JRC, and a few other carbines as well as doing a build. I opted to go for a build since it was the only way to get what I wanted. The rifle came out nice but my first 2 trips to the range have not been without issues. Twice, the bolt has hit the bolt catch lever and caused it to bend making it stick in the activated position. Yesterday, it even cracked the bolt catch.
Here is a list of parts if anyone is curious. For the sake of typing it out NFA is (New Fronteir Armory)
NFA billet glock mag lower (assembled by them since a striped lower hasn't been in stock for a while)
Standard weight and length carbine buffer with their buffer plug (also provided by them with lower)
NFA LRBHO upper receiver
NFA 1:12 match grade 16" barrel
NFA AR9 one piece bolt
BCM Gun Fighter charging handle
Fortis Rev 14 rail
YHM 9mm muzzle brake
I won't say this has been a troubled build yet. NFA has been helpful so far but I'm waiting to see what they have to say on the issue. Originally I had their modular bolt and it wasn't machine properly not allowing the gun to cycle. They send me a one piece bolt as a replacement and that seems to be working well from what I can tell. Now that I can actually take the gun out and shoot it, I've had this issue.
This is my first 9mm AR so I'm not 100% sure what my problem might be. I'm thinking I could possibly have a buffer issue or it's an issue with the bolt hold open level, maybe the mags are putting too much pressure on it on the 2nd to last round where the bolt catch won't activate but it allows the bolt to hit it when it comes forward to chamber the last round.
I will say this, function checking the gun with snap caps the gun works flawlessly. You can sit there all day long with snap caps cycling the gun and every time the snap caps will feed, eject, and the bolt will lock back on the last round and it doesn't seem to hurt the bolt catch at all. If you take it to the range within 25rds or so the bolt catch will be bent.
I'm still waiting to here back from NFA but does anyone have any ideas or things to try? The first pic was from last weekend. You can visibly see where the bolt was hitting. The 2nd pic is from yesterday. It doesn't show as much impact damage but you can see the crack. The 3rd pic is the wear mark I'm starting to get in the lower. Literally that's from I'd say a combined 50rds.
Here is a list of parts if anyone is curious. For the sake of typing it out NFA is (New Fronteir Armory)
NFA billet glock mag lower (assembled by them since a striped lower hasn't been in stock for a while)
Standard weight and length carbine buffer with their buffer plug (also provided by them with lower)
NFA LRBHO upper receiver
NFA 1:12 match grade 16" barrel
NFA AR9 one piece bolt
BCM Gun Fighter charging handle
Fortis Rev 14 rail
YHM 9mm muzzle brake
I won't say this has been a troubled build yet. NFA has been helpful so far but I'm waiting to see what they have to say on the issue. Originally I had their modular bolt and it wasn't machine properly not allowing the gun to cycle. They send me a one piece bolt as a replacement and that seems to be working well from what I can tell. Now that I can actually take the gun out and shoot it, I've had this issue.
This is my first 9mm AR so I'm not 100% sure what my problem might be. I'm thinking I could possibly have a buffer issue or it's an issue with the bolt hold open level, maybe the mags are putting too much pressure on it on the 2nd to last round where the bolt catch won't activate but it allows the bolt to hit it when it comes forward to chamber the last round.
I will say this, function checking the gun with snap caps the gun works flawlessly. You can sit there all day long with snap caps cycling the gun and every time the snap caps will feed, eject, and the bolt will lock back on the last round and it doesn't seem to hurt the bolt catch at all. If you take it to the range within 25rds or so the bolt catch will be bent.
I'm still waiting to here back from NFA but does anyone have any ideas or things to try? The first pic was from last weekend. You can visibly see where the bolt was hitting. The 2nd pic is from yesterday. It doesn't show as much impact damage but you can see the crack. The 3rd pic is the wear mark I'm starting to get in the lower. Literally that's from I'd say a combined 50rds.
Last edited: