Bradd D wrote: "Some of the early prebans had a design flaw that was eventually corrected by Bushmaster. The correction came in the form of an upgrade in which you sent in your rifle and the necessary parts were exchanged. Bushmaster will do this for about $100. To quickly tell if the rifle you are considering has had the upgrade look to see if it has AR15 style pushpins to disassemble the upper and lower receivers. If so, then the rifle has had the new parts installed. If not, it's worth the $100 to have it done."
I have a pre-ban M17S that has push-pins (both front and rear). It had not had the "upgrade" (bought it new prior to any bans). I have been thinking about sending it back for the "upgrade" even though I have not experiencing any problems. In addition to the push-pins I know there are some other changes (ie. lower reciever mag well extended, etc.). My question is: Prior to push pins connecting the upper to lower, how was it done (screws?)? Other than the lower receiver mod, perhaps mine already has the internal changes and the $100 would be for nothing?