went to the range today, took my buddy.  he has one of the piston conversions on his rifle.

every other round or so, the piston would get hung up on the return stroke.  I'm pretty sure the knurled deal on the piston was getting hung up on one of the holes in the heat shield on the upper handguard, as when it happened I was able to get it to return to battery with the slightest pressure from a spend case applied through one of the holes to the knurled deal on the piston rod.  the area on the heat shield was buggered pretty good where I suspect the hang up is occurring.

although I'm nearly 100% positive this is where the hangups are occurring, he wouldn't let me fix it because he "was in a bad mood".

when this started happening, I had him remove the upper handguard and fire a few times.  worked fine like that.  but when I put the upper handguard back on, it hung up again, and he threw the rifle down, started yelling and cussing and generally acting like a spoiled little girl.

currently, the rifle in question has about 300 rounds through it.  today was the first time the hangups occurred.

any help or advice would be appreciated.

Want kind of handguards was he running?  Switch those out with a rail system and the clearance issue should be resolved.

running the handguards that came with the conversion.

I doubt he is gonna want to buy a rail system.  he is one of those guys that thinks an 80 leapers scope is a kick ass item and is as good as anything else.  (I tried to tell him that its crap and not worth it, but he bought it anyway)  he is also of the persuasion that he knows everything and he won't listen to folks who know better.  apparently he thinks that he is an expert on the platform even though this is his first EBR/centerfire rifle.

I could have fixed the issue myself by relieving the area in question, but he wants a 3rd opinion.

Offer to buy the rifle from him for cheap.

Hand guards are possibly upside down. There is a top and bottom on the conversions usually.

Is it posible that your barrel clamp is not properly placed where it will not interfere with the piston's action? Look closely, if the clamp is contacting the piston it will hold it in place rather than allow it to cycle rearward.  If so then loosen it up and move it a bit forward until it touches nothing but the housing.

ha ha, what a tool.  thats what he gets for buying a leapers scope.

but seriously, i hate folks like that.  if its the handguard then swap it.