9mm AR using a standard CAR buffer?

[Nordschleife]

Well, I've just completed my 9mm OLL build, however I'm still missing two critical parts; a magazine and a buffer. RRA said the magazines are back-ordered for an "uncertain amount of time" and the buffers are BO'd for another two weeks. I ordered a buffer from adco that's supposed to be in stock so now I'm waiting for confirmation.

While waiting for the 9mm buffer to arrive, I was wondering what my AR will act like if I were to chamber and fire a 9mm round with the carbine buffer. I've looked up previous threads, and granted the carbine buffer is almost half the weight as compared to the 9mm buffer (84 grams vs. 155 grams respectively).

Has anyone in here did this before? I'm kind of weary about trying this but if it works without damaging anyone/anything then I'm going to zoom over to the range for an AR breach loading session!

[WolfMansDad]

9mm uppers are recoil operated, not gas operated, aren't they? I can't imagine that you could damage your rifle with a heavy buffer. The worst thing that would probably happen is the rifle would have trouble cycling. What if the breech never unlocked? Well, then you'd just have a single shot, then have to operate the bolt manually.

This is all based on what I've read and on experience with pistols, but I doubt you could damage your rifle this way.

[idk]

I have a colt 9mm ar, I have never used any other buffer than the came with it. You are rite it is twice the weight of a standard buffer an H4 buffer doesn't even get close. The 9mm uses a blow back system and I think you could damage somthing or it might FTE like an over gased ar15 (.556). I've also heard the plastic mags that RRA sells have problems and to stick with the steal ones.
Roger

[twl]

Wait for the 9mm buffer.
The blowback system requires the extra mass of the heavy buffer to operate properly.
It will cycle too fast and possibly batter the gun from violent cycling if the buffer is too light.

[Solidsnake87]

I just finished a 9mm rifle. Get the buffer or risk damage to your rifle. Direct blowback is very hard on your rifle unless the heavier buffer is used. If you have a friend in NV, buy some Promag 32 round mags and mod them to 10. I just made a bunch of 10 rounders out of those.

[bwiese]

Make sure you're using the right recoil spring too - those *may* well be different btwn 223 and 9mm carbines.

Do beware that light/anemic 9mm rounds may not cycle your 9mm AR carbine properly. This is not the fault of the gun, but of the ammo. These guns were designed for subgun ammo, esp 147gr stuff. Anemic PMC 115gr ammo (and possibly Fiocchi, etc.) may not run the carbine that well. Don't try to fix the carbine for this ammo.

[REDHORSE]

I've shot many CAR-9s with various buffer weights.

I have the three carbine buffers: Standard, H buffer, and the RRA 9mm buffer. I've used them all with my 9mm upper with out any issues.

All the buffers will function fine with the 9mm upper. But, generally you want the heaviest buffer or/and spring combo you have to reduce the recoil & stress to your lower.

I generally bring the other buffers in my range cleaning kit, if I run into ammo problems. If I find that the ammo I'm shooting is too weak, putting the lighter buffer will often resolve the short stroking with weaker ammo.

Also using a chrome silicon recoil spring with the standard or "H" buffer (preferred) should work fine for a while if you don't have a 9mm buffer. I fired several thousand rounds this way, without any issues.

Recoil (the little you get with a 9mm) is just smoother with the 9mm buffer. Heavier the buffer the slower the bolt will cycles, therefore you get less powder fouling from the blowback, as the powder will burn in the barrel just micro seconds longer.

The slower cycling will also put less stress on your hammer pin, not really a big issue with a semi-auto.

The slower cycling will also probably make your 9mm dedicated bolt catch (if you have one, depends on your setup ie dedicated 9mm lower w/ pinned mag block and with Colt mags, etc..) last longer. The 9mm dedicated bolt catch tend to break more frequently than their .223 counterparts. I just replaced a Colt 9mm bolt catch in a friends dedicated 9mm Colt carbine earlier this month.

[REDHORSE]

The Q buffer from Slash @ AR15.com is probably the best 9mm buffer out there, from all the reviews I've read. It should help with eliminating broken Colt 9mm bolt catches.

http://ar15.com/forums/topic.html?b=7&f=25&t=263131

[Hitman]

The 9mm dedicated bolt catch tend to break more frequently than their .223 counterparts. I just replaced a Colt 9mm bolt catch in a friends dedicated 9mm Colt carbine earlier this month.

This is true. I had replaced my bolt catch twice already. But then I shoot alot of 9mm too.

[Nordschleife]

Hey all,

Thanks a lot for all your responses. I'm going to wait for the correct buffer to come in before firing the rifle....good points made about the stress and pressure being put on the rifle without the correct buffer and this build being blowback operated.

Well, I'll try and get some pictures posted up sometime soon.