scrub the hell outta the chamber, sometimes on a 22 the slightest bit of dirt in there will throw off the headspacin, i got a rem 22pump that' ll do them same, if i go too long (500) it;ll back the cartridges outta the chameber and the casings will rupture

Did you ever think that the spring is weak and the firing pin may be just a little to short?

Sounds like nice warm box and trip back to Marlin for your 39.

Good Shooting