I just have my dad's Universal with a weaver 2.5X scope. It's unfortunately not very reliable, however it is surprisingly accurate. I've killed some big hogs, lots of varmints and a deer at 115 yards with it. I've got a lot of respect for those little. 30 caliber soft points. I wish I had a more reliable rifle.
It might be that the piston is grunged up and not hitting as quick as it should. The pistons in an M1 Carbine aren't as easy to remove as an AK or an SKS. They're only about an inch long and held in position by a nut that's staked into place. You need the wrench to remove the nut, and typically the nut is replaced with a new one anytime it's removed.
