I bought a pistol buffer and intended to use it for this build, but I didn't know jack about the colt 9mm setup when I started (note that these comments may or may not apply to the oly system - I just don't know).
Anyway, the pistol buffer uses an insert the fits INTO the hollow ass-end of the ar-15 bolt carrier. The recoil spring then fits into this insert. Also, the pistol buffer assembly includes a shaft that the recoil spring fits over to help ensure it doesn't kink under compression.
Now, the colt-style bolt (note that the colt system uses a single piece bolt + bolt carrier that I'm calling the "bolt") is SOLID in the rear due to the added weight. This creates two problems: there's no where to place the insert and there's no way this is going to be able to recoil over the shaft that contains the spring.
One solution might be to remove the added weight at the rear of the 9mm bolt, but I'm reluctant to take that step. With a pure blow-back system like this, the extra weight seems like a good idea.
Joe