I think first we should find out why it comes open. In my case it was because the ammo was too long. My MGM 12 inch 44 mag. barrel started doing it. My friend who is very smart when it comes to Contenders told me to check that first. I was loading 240 gr cast truncated cone bullets and didn't realize a little bit of extra effort was needed to close the gun. The shoulder of the bullet was being slightly engraved by the end of the chamber. After a while, the interlock failed to prevent it from firing, thus causing it to come open. My solution was to buy a bolt from MGM, which is the same as the TC bolts. I chose to order from MGM only because I wanted to get it back in action, and didn't want to take a chance of S & W taking their time sending a new one.
This same thing happened back in my handgun silhouette days with a TC 10 inch 30-30 barrel. Back then TC replaced the 1 piece bolt with the newer 2 piece bolt.
To check for ammo fitting, use the barrel off the frame as a gauge. The cartridge must be at least flush with the end of the barrel (pretty much gravity drop).
