Quote Originally Posted by One More Time View Post
My 9mm upper was an 8", I used Endo mags.

I used a KVP BCG with a Rifle (Green) spring.
You pretty much want the reciprocating mass around 21 - 23oz.
I was using a Law folder and had to cut the carrier's internal weight off a bit to fit the adapter for the folder, with an A5H4 buffer I was at 22oz.
Ran like a champ and didn't trash the brass on the way out.
Vltor has dedicated 9mm buffers now up to 10oz I believe.

My 5.56 upper is using an A5 action.
To use The 9mm upper I used a 5/8" nylon spacer for the A5 tube with the A5H4 and green spring.
A regular carbine tube doesn't need a spacer.
Also very useful information. Thanks.

I may run an a5 in this, I have one in the parts bin.