I have a colt Ar-15 in 9mm with the Colt 9mm SMG 2 pc mechanical buffer. [ See http://www.biggerhammer.net/ar15/buffers/ ]

Question: is there and advantage to this buffer for the 9mm?  Any thoughts or recomendations would be apprecaited.  

Unless you are shooting a full auto RR gun I cant see any real benefit to it. The way I understand it is the SMG buffers are to help reduce the ROF in full auto guns.

[beer]

That is not really a 9mm buffer.  The two piece buffer you have was developed by Colt to be used in the Colt Commando with 11.5 inch barrel to slow the rate of fire.  Colt made a 9mm buffer that was solid and heavier than the regular buffer, but it did not have the two piece configuration.  As mentioned, the heavier buffer for 9mm and the two piece buffer for the Commando were used to slow down the rate of fire.  If you have a problem with bolt carrier bounce in your 9mm, then use the heavier 9mm buffer or the two piece Commando buffer you have.  Otherwise, it does not really serve any purpose in a semi-auto 9mm.

Charles Tatum
Alamo Professional Arms

I was having quite  a few stovepipe jams and double feeds.  It is a semi-auto.  
I was going to try a conventional AR buffer to see if this solves the problem.  The conventional buffer is much lighter than the two-piece and I wonder if this is the correct direction to go?

Might be worth a try.  If you do switch buffers and would like to sell your heavy one, please lemme know.  It would work great in a 7.62x25 project I'm putting together.