Do you have the stock? If so measure the length of the hole. Come on Rory, this ain't rocket science. To measure the length from where the head of the bolt sits to where it comes out of the stock. just run something with a bigger diameter than the bolt shank from the butt end to block the hole and run a cleaning rod from the action end. Mark the cleaning rod where the wood ends on the action end. Close enough to determine the length of the bolt. If that's too hard or you don't have the stock just ask and I'll send you one of each length. You can pay me for the one that works and send the other one back. If you don't presently have a stock I got all the time in the world to wait for you to get one and figure out which bolt works. I'll be retired for the rest of my life.
Go tell the Spartans,Travelers passing by,That here,Obedient to their laws we lie.
I'm older now but I'm still runnin' against the wind
To measure the length from where the head of the bolt sits to where it comes out of the stock. just run something with a bigger diameter than the bolt shank from the butt end to block the hole and run a cleaning rod from the action end. Mark the cleaning rod where the wood ends on the action end. Close enough to determine the length of the bolt. If that's too hard or you don't have the stock just ask and I'll send you one of each length. You can pay me for the one that works and send the other one back. 
