We sell the best Ruger 77/50 209 conversion. Seals the breech, stops the firing pin from being shot rearward (which frequently breaks the sear) and allows one to use Black Horn 209 powder. http://www.badgerridgeind.com/the-badgers-den/category/ruger-7750
We also have the original manual hosted on our website: http://www.badgerridgeind.com/ruger7750.html
Bolt disassembly is detailed in the manual but is really easy, twist the bolt plug clockwise (like you were trying to tighten a screw), it will pop out of the cocked notch, then place a 3/32 pin (or a drill bit if that is all you have) in the hole on the cocking piece, then twist counter clockwise (like you are unscrewing it) and you can remove the firing pin assembly.
If you are having miss fires, I'd strip the firing pin assembly all the way down (but you really need a bolt tool for that). I have examples on how to make one if you have a welder and some stock, and some skills. I'm working on selling those too. http://www.badgerridgeind.com/firing-pin-tool.html
If you don't want to tear it down, I can do it for you too: http://www.badgerridgeind.com/store/p51/MainspringReplacement
Hope to help.
Tom