I've looked for questions relating to this, but not to my specific question (and can't look through all the hundreds of threads here).

I've shot probably 1,000 rds or so through my 15-22 with no problem using mainly CCI standard velocity (1,070 fps). Only recently it has failed to cycle. The last couple shots before it quits you can hear and feel the shots lose velocity.

I haven't modified anything on it, except for cosmetic accessories like grips and such.

I was using a 6 in barrel extension tube (looks like a fake suppressor) to cut down on the noise, not sure if it's had any effect on the action or not. I've stopped using it since the problem.

I've also noticed that the velocity fluctuates using the same ammo. Some shots are much louder than others, some seem to come out with a whimper. Maybe the firing pin is making inconsistent contact with the primer?

Long story short, it's been cycling SV just fine, but now it's not. Just wondering if you guys have any ideas. Many of you are much more knowledgeable than me, I basically like to plink around in the back yard.