I just switched to a 6 pos collapsible stock on my Colt SP1 and my 9mm RRA upper is now single shot. It seems to be short cycling. It cycles enough to strip a fresh round but not enough to cock. Do I need to go to a Colt style buffer? Or are there any other fixes?

Are you sure that you've got all carbine parts for your stock? (spring, buffer)

This is a pretty unusual problem.  I'm assuming that your stock really collapses and you have a real carbine buffer tube an not a notCollapsable fake telestock with a rifle length buffer tube, or worse yet a notTeleStock with a rifle length tube on the outside and carbine length on the inside.

Is it a bastard to retract the bolt the whole way?

Your lower being an SP1 lower should have nothing to do with anything assuming your upper is adapted properly.

FYI, a 9mm buffer is carbine length and heavier than a standard carbine buffer or H-buffer.  I've been running one in my M16 with a 11.5" 5.56 upper and it slowed the cyclic rate down over the H-Buffer that I had.  It's a good thing.

I have got everything that I am supposed to have (Carbine buffer and spring) and it cycles okay by hand. The stock I have is a Rock River 6 pos that I got from Brownells.

I don't know if this will have any bearing on your problem but I've got the RRA 9mm upper with the 9mm buffer and hammer but on a semi-auto lower and started have short cycle problems. Seems I decided to try a thin coat of grease on the bolt instead of the CLP because under rapid fire I would get a lot of vapor/smoke from the charging handle gap and it would get on my shooting glasses. I have 1500/2000 rounds throught the gun, nothing else was changed and the darn thing started short cycling to the point the fired cartridge would not eject fully and get jammed in the receiver. I cleaned all the grease out of the receiver and bolt, soaked the thing in CLP like I normally would do and and the rifle went right back to shooting like a champ. The point is The grease was slowing the bolt because it was stickey and thick. I was wondering if the new buffer tube might have enough drag to slow the buffer down and cause the short cycle. Are you using your first buffer and spring or a new buffer and spring from RRA? Try cleaning the buffer tube, spring and buffer with solvent and see if this helps. I didn't notice any difference in the operation when I pulled back on the charge handle either when I had my problem.
    By the way, I shoot only the cheap stuff from WalMart, the 100 rounds in a box for $11 stuff so this is not high power stuff.

Well, it seems like my problem was not short cycling after all. I went out in the backyard today and done some test firing and upon examining the unfired cartridges I noticed slight indentations on the primer face. Knowing that the 9mm firing pin is a "spring loaded" one I knew something was wrong. I took out the original fire control parts (early Colt SP1) and replaced them with new Bushmaster internals and the problem was remedied. Thanks to all who responded.