Put this in the pcc forum but didn't get a response. Figured I'd try here

I'm in the market for a pistol caliber carbine to use in uspsa and for general fun. I have looked at a bunch of different options and I really like the Colt a lot. I have a Cz EVO pistol and have thought about the carbine, but I may try something different. Also the sig mpx is interesting but it's a lot more expensive for not much gain (although a non blowback mechanism is pretty cool). Mp5's are too expensive, otherwise I'd probably go that route. The Colt is only about $900 so it's not too much more than comparable 9mm Ar's. With an ar type rifle, I can use a lot of stuff I already have for ar's like triggers, etc.

What can anyone with a 6951 tell me about them?

They've been around a long time, work well, lifetime warranty. I doubt you'll find anyone speaking bad about them, though folks might offer alternatives.

If the 9mm Colt SBR's were around last year before I registered my SBR, I'd have gotten one of them.

I have one. Love it. Wouldn't trade it.

I've had both the 6450 & 6951's over the years & I love them!
I was lucky enough to get a true lower that had never been anything ,but a receiver & SBR's it!
Got my stamp back & it is headed to engraver to be forever a Family heirloom!
Very happy with all of them & have never really had any issues except crappy re-loads.
Get one & enjoy it forever!

I have one, it works fine and it's fun.

I put a Trijicon SRS on it and it's pretty fast on steel targets.

If you get one, keep looking on Palmetto State Armory for magazines.

Every once in a great while they put their metalform mags on sale for about $12.

The Colt for $900.00 will always going to be a safe buy. They are extremely reliable using Metal Form or PSA (Metal Form made for PSA).

But, if it was me I would just build one using a dedicated 9mm Colt mag lower from QC10, PSA, Black Creek Precision. In this day and age having an adapter block pinned to a standard lower is so old school and just looks plain ugly. Don't get me wrong I've used a mag block for over a decade and it worked well.

Also, it will make for having a more comfortable mag well grip.

True, except if you're SBRing it and have limited funds.  In that case, you may be better off with a regular receiver and mag block; that way you can have more than one short barreled upper on the same registered lower; 5.56, 9X19, 300BLK, for example.

If all you want is a 9X19 carbine, and don't want to spend the coin on an MP5, then I'd look for a used IMI Uzi.

That would be good if you got a regular AR lower and bought a removable adapter, but the Colt adapter is pinned in, so not removable.

It IS very nice to have a Colt roll mark specific to the 9mm, rather than a generic roll mark, but then any other makers would also have a 9mm only rollmark, so meh.

The 6951s seem to only have 1, maybe 2, production runs a year which can make them difficult to find depending on when you look.