I noticed during some chrony strings that occasionally I would fire a “dud”, or one that was much less than the others. Cranking along at 950 fps, and all of a sudden, 500! WTFO?!? I think the problem was the bushing under the bolt handle binding on the frame cutout.
I had already made a new bolt handle since the factory fuzzy padded one wasn’t to my liking. Mine’s black delrin. I started out machining the “extension” piece on the same delrin. When I tightened the screw, it squished out a lot. I cut that part off and reused the factory plastic bushing which was a much harder plastic (glass filled?). Turns out, this factory bushing left a lot to be desired (sucked) as well.
I’m pretty sure it was allowing it to bind. See picture below. This picture is through the bottle fitting, looking at the back end of the breech plug. The breech plug is installed backwards to get a feel for how much slop was present and to allow me to photograph the handle interference.
And evidence of the binding.
If the handle was forced over to full left or right it would feel like it wanted to hang up a little. Sometimes this wouldn’t affect the shot, sometimes it would.
Since delrin wouldn’t cut the mustard, I made a new bushing out of brass. It’s longer than OEM, but still 0.250″ diameter (the slot is 0.260 on mine). The flange is 3/8″ diameter since that’s the rod stock I was making it from. #10 clearance hole through the middle (#11 drill bit?).
Below is a shot of the two different parts.
Here is the finished product. It is shown at the full-left engagement point. I lightly lubed the slot and shot a nice string afterward. No more duds!