AR9 beating the shit out of itself

[slap shot]

having trouble keeping this AR9 running. This happened twice so looking for recommendation. The buffer is smashing into the retaining pin and destroying it to the point of the buffer not being retained. Last time it just stopped running. This time the pin lodged itself in the bolt, completely locking everything up. Is this simply a case of needing a heavier buffer when running 9mm?

 

[Golddiggie]

What weight buffer are you using now. From what I recall during my PCC build investigation, they used heavier/different buffers than you would use for 5.56/223/300blk.

 

[jayhitek]

AR9 require a special buffer and spring.

 

[milktree]

If the buffer is smashing into the spring, it makes me think the bolt is too short. The limiting factor for the buffer should be the bolt, which is limited by the barrel. If there's slop between the back of the bolt and the front of the buffer, each shot will slam the front of the buffer into the retaining pin.

 

[slap shot]

Just weighed it. 3 ounces. Any recommendations or should I just use the google?

 

[slap shot]

I think i need something like this. Oh well, live and learn. 9mm Buffer (5.5oz) and Premium Mil Spec Buffer Tube Kit

 

[fmyspray]

I think i need something like this. Oh well, live and learn. 9mm Buffer (5.5oz) and Premium Mil Spec Buffer Tube Kit

Go see Slash @ heavybuffers.com and never have to worry about it again. 9mm AR's will also break the bolt release. Been there. down that.

 

[exo]

Not sure what the spec is, but consider checking the location of the buffer retainer. I had a lower once (one of those G3 AR frankenrifle things) where the hole for it was in the wrong spot, causing much damage to the face of the buffer (I think the bolt carrier was smashing into it).

 

[slap shot]

Thanks guys, I’ll report back once I get some parts in and get to the range

 

[Uzi2]

Your pictures don't show very much at all.

A 9mm AR upper requires a heavier buffer and spring than .223/5.56. If you haven't changed them both out you need to do so.

 

[slap shot]

Your pictures don't show very much at all.

A 9mm AR upper requires a heavier buffer and spring than .223/5.56. If you haven't changed them both out you need to do so.

I was really only showing the buffer retaining pin jammed into the bolt and the damaged pin and spring.

 

[wmass]

Mine did the same. The retainer pin was so beat up and bent that it ate up the face of the buffer. The burs it created would make the buffer stick in the tube. It’s usually two things. Either the carrier is too short or the hole for the retainer was drilled incorrectly. There’s a couple fixes I’ve seen. An offset retainer, a steel retainer, and some companies will bevel the buffer face allowing less contact with the pin and more with the carrier.
Slowing the carrier will help but eventually it will still fail from the contact.

 

[Fixxah]

The buffer shouldn't touch the pin unless the upper is flipped open or renoved. BCG not correct us my guess.

 

[slap shot]

The upper was purchased complete with BCG installed, so I don’t think it’s the wrong length. I don’t understand the buffer not touching the retaining pin. On all my ARs the buffer rests on the retaining pin.

 

[slap shot]

Not sure what the spec is, but consider checking the location of the buffer retainer. I had a lower once (one of those G3 AR frankenrifle things) where the hole for it was in the wrong spot, causing much damage to the face of the buffer (I think the bolt carrier was smashing into it).

The thing is I’ve run lots of rounds through this lower in 5.56. Hoping the heavier buffer and correct spring solves the issue.

 

[jayhitek]

The upper was purchased complete with BCG installed, so I don’t think it’s the wrong length. I don’t understand the buffer not touching the retaining pin. On all my ARs the buffer rests on the retaining pin.

I agree with you on this one. It's a hunk of metal sitting in front of a large spring and held in place with a pin... How can it not touch the pin?? The pins job is to lock the buffer at an exact spot.. And when you close the upper the bcg is sitting face to face with the buffer. Not pushing the buffer back.

 

[jayhitek]

The thing is I’ve run lots of rounds through this lower in 5.56. Hoping the heavier buffer and correct spring solves the issue.

You have the right game plan. I think you problems will go away once You replace the pin and get the correct buffer and spring combo.
It's a whole different product. My AR9 buffer spring came with the very heavy buffer, shorter spring, and a cap plug thing that goes all the way at the end of the buffer tube on the other side of the spring.
(some people use this same trick of putting a few quarters inside their tube to compress the spring a little more).

 

[bfm]

JP - Buffer Springs and Silent Captured Springs

Get one made for 9mm. Go heavy if worried.

 

[Fixxah]

The upper was purchased complete with BCG installed, so I don’t think it’s the wrong length. I don’t understand the buffer not touching the retaining pin. On all my ARs the buffer rests on the retaining pin.

No it doesn't. Only when you open the rifle. It is only to keep the buffer from popping out when you are srevicing the rifle.

Look at your other ARs and you can see the buffer move when you close the upper to lock in the pin.

Post some pics. It isn't rocket washing.

 

[slap shot]

One

No it doesn't. Only when you open the rifle. It is only to keep the buffer from popping out when you are srevicing the rifle.

Look at your other ARs and you can see the buffer move when you close the upper to lock in the pin.

Post some pics. It isn't rocket washing.

Understand you now but I’m not using the right buffer and spring so I’ll look at other possible causes once I get that sorted.

 

[bfm]

 

[slap shot]

These are great but $$$.

 

[Coyote33]

What is an AR9? I know the AR7 is the "survival rifle," or something like that.

 

[slap shot]

What is an AR9? I know the AR7 is the "survival rifle," or something like that.

AR in 9mm. This happens to be a pistol but it can also be a carbine.

 

[milktree]

You have the right game plan. I think you problems will go away once You replace the pin and get the correct buffer and spring combo.
It's a whole different product. My AR9 buffer spring came with the very heavy buffer, shorter spring, and a cap plug thing that goes all the way at the end of the buffer tube on the other side of the spring.
(some people use this same trick of putting a few quarters inside their tube to compress the spring a little more).

This fixes the "bolt smashing the bolt stop" problem, it does *not* stop the OP's problem.

 

[bfm]

These are great but $$$.

Yeah. I have not moved to them myself either for that reason but will probably buy them for any future builds.

Same with the Geissele products. I have moved most of my ARs to SSA-E triggers, but only a few to their charging handles. Anything in the future will probably have both.

 

[slap shot]

This fixes the "bolt smashing the bolt stop" problem, it does *not* stop the OP's problem.

We shall see. Riley’s actually had a heavy buffer on the shelf. Gonna load up a few mags and report back.

Honey badger don’t give a shit. Lol.

Ok: ran 75 rounds without issue. Feels better but I’m not calling success yet. Time will tell

 

[shootymacshootface]

Fixxah got it right about the pin. I removed mine to make removing the buffer and spring easier. You just have to remember to grab it as you open the two halfs of the ar.
Also put spacers behind the spring to only allow the bolt to go 1/8" or so beyond the catch. I found that heavy reciprocating components and a weak spring work very well. Mine feels almost like a 22lr.