AR9 bolt hitting bolt catch lever

[LT1MCSS]

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.

 

[71montess]

A bad spring in the bolt catch ? For it to be in play it might be hanging up.

 

[LT1MCSS]

A bad spring in the bolt catch ? For it to be in play it might be hanging up.

It doesn't seem broken. I have extra springs but when I replace it, it seems to operate normally.

One thing that kept confusing me though is how can I function test this as many times as I want and not have a problem but when I fire the gun break it in ~25rds or so. The nne thing I wasn't doing with the snap caps though though was dry firing the gun. I assumed it was the bolt hitting the bolt catch so I was only testing cycling and the gun always cycled fine. I started to think maybe I wasn't looking in the right place.

I literally just finished checking this now and I'm still not 100% sure this is my problem but here is my theory. I grabbed one of my other rifles I have a Geissele trigger in to check it's function vs my AR9. The Geissele hammer has a higher cut out in it to prevent the hammer from hitting the bolt catch. The standard trigger in the AR9 does not. It can actually impact the bolt catch. Because it's kind of a rainy day I decided to take the trigger out of my other rifle and put it in the AR9. Below are the pics. When the hammer comes forward with the standard trigger it actually impact the bolt catch forcing it in the direction it bends. Actually when it jams up it's in the same position that it is when the hammer is at rest up against the catch.

Standard Trigger

Geissele Trigger

 

[71montess]

Triggers should be ok with a ramped bolt.

 

[reveille]

Mine broke the other day too. I took all the precautions. I used a 9oz buffer and wolf heavy spring. But it still broke. It was a delton lpk. The heavy weight is supposed to slow down the bolt and prevent it from breaking bolt catches. I need a better bolt catch and I'll go from there.

 

[LT1MCSS]

Mine broke the other day too. I took all the precautions. I used a 9oz buffer and wolf heavy spring. But it still broke. It was a delton lpk. The heavy weight is supposed to slow down the bolt and prevent it from breaking bolt catches. I need a better bolt catch and I'll go from there.

It had the basic one you'd get in any lower parts kit from NFA and that's what I replaced it with. I had a spare Seekins on. The only reason I didn't put that in is because I didn't want to ruin it without knowing what the issue was. The 2nd pics I put up were with the Seekins bolt catch because that's all I got left.

 

[peterthefish]

No experience with Glock 9mm lowers (I have a few Colt style lowers) but a heavier buffer designed for 9mm seems to be recommended.

 

[LT1MCSS]

No experience with Glock 9mm lowers (I have a few Colt style lowers) but a heavier buffer designed for 9mm seems to be recommended.

I had been doing some looking into the heavier buffers too and found this over on AR15.com.
Standard CMT carbine buffer - 2.9 oz.
CMT H buffer - 3.8 oz.
CMT H2 buffer - 4.1 oz.
Armalite H3 buffer - 4.7 oz.
RRA 9mm buffer - 5.5 oz.
ST-X SS 9mm buffer - 6.0 oz.
ST-9X SS Extended 9mm buffer - 8.5 oz.
ST-SST - 7.0 oz
HeavyBuffers.com.....ie Slash
9Q 8.5 oz.
9Q-T extra heavy.....suppressor use, 12 ounces


I really don't care if I have to buy a hardened bolt catch, heavier buffer, different trigger, whatever it may be. It's more I just don't want to throw money blindly at the problem. It sounds like a ST-9X SS (8.5oz) buffer may be worth a shot or the 9mm-Q Buffer (also 8.5oz) where even on the website it says it was designed specifically to solve the issue of broken bolt catches.

 

[LT1MCSS]

Update: I sent an email off to heavybuffers.com but it's looking like that is going to be the next next is to try an 8.5oz buffer over the 3oz NFA gave me.

 

[peterthefish]

Let us know how it works out. My PSA 9mm buffers are about 5.3 oz. If the 8 oz buffer doesn't cause short stroking I bet it'll be a real soft shooter.

 

[LT1MCSS]

Clint at HeavyBuffers got back to me last night which I was surprised at being Sunday. I told him my setup and asked if he recommended the Q buffer and he said it should work very well with the Wolf XP spring. I could have went with Spikes since it was a little cheaper but Clint seems like he was on the ball and the little guy. I decided to try him out. He even replied back Aat 11PM Thanking me for my business. I can't say it will work yet but I will update this post when I get back to the range. It won't be this week me since I'm away but probably the week after.

 

[DrBurnsides]

Quick question.. This bolt catch looks a little different from the bolt catch on my AR9..

This is for a colt magwel AR9 though...


https://thebuffalo.us/shop/9mm-builders-kit/

 

[bigblue]

Actually the problem is the length of a 9mm bolt vs the M16 bolt with carrier and that the buffer tube was designed to use the M16 BCG.

 

[LT1MCSS]

I got back out to the range today with the rifle. The good news is i didn't bent the bolt catch with the Heavy Buffer I got. The bad news is the hammer wasn't getting pushed back when firing so the trigger wouldn't reset but it would chamber the round. It looks like another range trip. The bolt catch is also extremely hard to activate simply by hand now. I did get the Wolf XP Spring too so another thing I can try is the Heavy Buffer with a regular spring. The Wolf is about an inch longer. It looks like another range trip to test.

 

[peterthefish]

I got back out to the range today with the rifle. The good news is i didn't bent the bolt catch with the Heavy Buffer I got. The bad news is the hammer wasn't getting pushed back when firing so the trigger wouldn't reset but it would chamber the round. It looks like another range trip. The bolt catch is also extremely hard to activate simply by hand now. I did get the Wolf XP Spring too so another thing I can try is the Heavy Buffer with a regular spring. The Wolf is about an inch longer. It looks like another range trip to test.

Are you using the Geiselle trigger / hammer?
Is your bolt ramped?
Does the bolt hold open on the last round?

 

[LT1MCSS]

Are you using the Geiselle trigger / hammer?
Is your bolt ramped?
Does the bolt hold open on the last round?

The bolt was holding open properly on the last round but the hammer wouldn't go back and reset. I didn't shoot it enough to see if the bolt catch would break though lol. At least the little I did shoot it, it didn't break yet


I had put in the Geissele G2S along with the Heavy Buffer. It is ramped, this is the bolt:
https://newfrontierarmory.com/shop/ar-9-9mm-bolt-carrier-group-bcg-glock-colt-compatible/

I read an article on AR15.com where someone had the same issue resetting the trigger and was told they didn't have enough hammer height to work with the bolt. I switched back to the original trigger and am going to try again.

 

[peterthefish]

The bolt was holding open properly on the last round but the hammer wouldn't go back and reset. I didn't shoot it enough to see if the bolt catch would break though lol. At least the little I did shoot it, it didn't break yet


I had put in the Geissele G2S along with the Heavy Buffer. It is ramped, this is the bolt:
https://newfrontierarmory.com/shop/ar-9-9mm-bolt-carrier-group-bcg-glock-colt-compatible/

I read an article on AR15.com where someone had the same issue resetting the trigger and was told they didn't have enough hammer height to work with the bolt. I switched back to the original trigger and am going to try again.

If the bolt holds open but the hammer doesn't reset it's an issue w your hammer / bolt combo. My S3G will not work with a ramped bolt. It works fine w an unramped bolt. Basically, the hammer doesn't get pushed down far enough to catch the disconnector.

You can function check without being at the range. Cock the gun, pull and hold the trigger, then cock again. The hammer should not catch / reset. However, if you cock without holding the trigger, the hammer will most likely catch.

A standard trigger group w/ a ramped bolt should function check fine.

Hope that helps, good luck.

 

[LT1MCSS]

Let us know how it works out. My PSA 9mm buffers are about 5.3 oz. If the 8 oz buffer doesn't cause short stroking I bet it'll be a real soft shooter.

Thanks for the info. After updating this thread and reading on AR15.com I removed the Geissele trigger and put the stock Mil-Spec trigger back in. I got back to the range today and was able to shoot 175 trouble free rounds so I'm happy with that. I only stopped because I only had Federal AE 124gr left and for whatever reason the rifle hates that ammo. It always shoots but I have serious bullet setback issues with that ammo. I'm willing to write that off as the ammo though as other 115gr and 124gr ammo works well. I don't have any 147gr.

Here is a pic from 2 weeks ago. I had a similar instance today.