[9097]

It sounds like the magazine latch plunger (Part B-36) is binding. You might check it by removing the magazine and then looking into the magazine well to observe its movement while operating the magazine release. If it's not moving freely, it probably just needs a good cleaning. Try using dry lube when reassembling. Oil tends to catch and hold any blowback residue and will eventually gum up the works.

Yes, that is why I run my plunger clean and dry, no lube except on the outer surface away from the cylinder that the plunger runs in.