Well , I am an "old timer" when it comes to firearms, but I am brand new to this forum. I do however need some assistance. I have recently purchased a H&R 45-70 Trapdoor Carbine. It is in unfired condition and I think it was built in 1973. I understand that there is a safety issue with these rifles as relates to the breechblock locking cam and the way it attaches to the thumb lever shaft. It seems that unlike the original trapdoors, the H&R locking cam is held in place, on the round thumb lever shaft ,by a single set screw. If the set screw ever loosens or looses purchase on the round shaft, even a little, it allows the shaft to turn inside the cam thereby messing up the "timing" of the locking cam with the lever and allowing the breechblock to possibly fly open and the fired case to fly back at the shooter's face. That don't sound like any fun at all! I have also been told that there are a couple of easy fixes for the problem. If any of you guys are familiar with this problem or better yet maby have even done a fix for the problem, please let me know. Even if you have ever dissasembled the H&R locking cam and thumb lever mechanism, I would like to ask you a few questions. All responses will be greatly appreciated. Thanks, RonW