Nice that the fabricator is trying to get the maximum diameter so he can get the bigger hole inside.... Compare that to the flow through bolt on a QB and it's a LOT bigger, the QB isn't even close to bore size.... I notice that the center hole in the flow through is so deep that it nearly cut through to the O-ring groove, that's why the bolt failed....

I replaced the flow through on a QB (one that I had drilled out for more flow) with an extended probe instead and picked up 30 fps on a 900 fps gun.... Other than the flow through style seating all pellets to the same depth and square I can't see any reason for using one....

Bob