So I got a short upper for my m16 its 11" I think, currently using a 14.4 colt upper. I put this no name upper on my m16 and it worked fine but the recoil was way harder than the 14" is this normal . I'd say the recoil was double or more with the short upper.
I'm using a carbine stock with a h2 buffer?

Shorter upper usually means shorter gas system and quicker/harsher recoil, with rougher extraction.

Usual fix is a heavier buffer to tame the overpressure, or taming the gas port on shorter uppers to prevent overgassing.

FWIW, I run a 7.5" DPMS Kitty-Kat upper with a standard carbine buffer and it's rock solid.  Lots of muzzle blast and slightly harsh recoil from the short gas system, but very reliable.

SBRs are best paired with suppressor a with will reduce the felt recoil.