Change 9mm AR15 buffer for use with suppressor?

[Bret]

I have a 9mm factory SBR Rock River Arms AR15 that runs like a champ. I've removed the flash hider so that I could thread my TiRant 9 suppressor on. I then got to thinking that I need to install a heavier buffer. Then I got to thinking more and realized that the rifle is straight blowback and there is no gas system, so I don't need to change the buffer. Then I got to thinking even more and remembered that I sometimes have to change to lighter recoil springs when shooting my suppressor on my handguns. Finally, I decided that it would be best to simply ask. So do I need to change to a heavier or lighter buffer when running a suppressor on a 9mm AR15?

[Clint]

Straight blowback is a form of gas system acting directly on the case.

The suppressor will increase gas impulse slightly, but probably not enough to worry about if the buffer is already heavy enough.

[hk_shootr]

The RRA 9mm ships with a Colt style 5.5oz buffer

[hk_shootr]

Oops......double tap

[Bret]

The suppressor will increase gas impulse slightly, but probably not enough to worry about if the buffer is already heavy enough.

Good to know. I'll run it with and without the suppressor to see if there's a difference in the ejection distance.

The RRA 9mm ships with a Colt style 5.5oz buffer

Though I don't know about the weight, they do not look the same. The RRA is on the left and the one from my Colt SBR is on the right.


The RRA has a roll pin through it that allows the rear of the buffer assembly to slide front to rear relative to the rest of the buffer assembly.


I can't figure out what the thought is behind the different design.

[Clint]

Here are some good threads that discuss the issues around 9mm buffers.

Short version of the hot setup: Longer & heavier buffer with stronger action spring.


https://www.m4carbine.net/showthread...AY-HAVE-EXTRAS

https://www.m4carbine.net/showthread...ring-questions

https://www.m4carbine.net/showthread...s-for-Colt-9mm

[Bret]

Here are some good threads that discuss the issues around 9mm buffers.
Short version of the hot setup: Longer & heavier buffer with stronger action spring.

I read through most of the threads. They seem to discuss how to setup a 9mm, but are not oriented around taking a well functioning 9mm and getting it to run with a suppressor. Given that my RRA is running reliably, do you agree with hk_shootr that I'll probably be ok leaving things as is? Or, is it your experience that most of the time the spring or buffer needs to be changed when running a suppressor on a 9mm AR15?

[Clint]

Proper setup with a heavy buffer should allow function either way.

Go ahead and try what you have now, but don't be surprised to have similar experience as below:

https://www.m4carbine.net/showthread...pressed-9mm-ar

https://www.m4carbine.net/showthread...ks-9mm-and-you

https://www.m4carbine.net/showthread...pressed-9mm-AR

I read through most of the threads. They seem to discuss how to setup a 9mm, but are not oriented around taking a well functioning 9mm and getting it to run with a suppressor. Given that my RRA is running reliably, do you agree with hk_shootr that I'll probably be ok leaving things as is? Or, is it your experience that most of the time the spring or buffer needs to be changed when running a suppressor on a 9mm AR15?

[6mmAR15]

Give Rudy a call and Macon Armory and ask him...…...he usually answers the phone and more than happy to answer your questions...…..I consider him a Guru when it comes to PCC...……

[hk_shootr]

Though I don't know about the weight, they do not look the same. The RRA is on the left and the one from my Colt SBR is on the right.

Interesting. My 9mm Colt carbine that I bought new about 15 years ago has a buffer that looks exactly like the RRA you pictured. Is your Colt a newer model? Searching Colt 9mm buffers show the design to be just like I have.

I would suspect Macon Armory will recommend changing to a buffer that weighs 8-12oz

You might think about getting a buffer tube spacer for your RRA as well.