My dad has had a Nylon 66 in Seneca Green since new. Shot it all the time as a kid; coon, rabbit, squirrel. Been sitting in the closet for the last 30 years only to come out for the occasional coon in the barn. Receiver cover hasn't been off for at least this long.
His grandkids, including my daughter, are all getting to the age of learning to shoot. Pulled the nylon out, removed the receiver cover, cleaned the bore. Cover back on, ran a hundred rounds through it. Lots of spent shells caught in the closing bolt, probably 20~25. 9 or 10 rounds jammed feeding in, caught by the bolt half way into the bore.
to help with dis-reassemble. Took a while but everything seemed to go good. Took it out, one round in it, fire perfectly. Loaded another round, perfect. Filled the magazine, first round perfect, second round the trigger wouldn't pull. Racked the bolt to clear the round and load a new one. Tried it again and same thing. First round fired fine, second round dead trigger like it won't cycle the bolt and hammer back to reset the hammer on the sear.
I have tried it about thirty times now and it's the same thing every time. Have primarily used Winchester white box 36 grain, but have tried CCI mini-mags 40 grain as well.