Which Holes To Plug?

[jnagy]

When plugging the holes on a Hatsan AT44 valve , which ones do you plug and which one do you leave open? Does it matter or do you just pick one to leave open and plug the rest? Thanks.

[Bwalton]

In Bobs mod he has one hole that lines up, in myAT44-10 it does not line up, So I plug the two bottom holes and left the rest open, then tune with the chrono and the hammer spring.

[rsterne]

Ideally, leave the top hole, 2 holes, or 3 holes open, plugging at least the bottom 3 holes.... If you have a single top hole that lines up (or make it line up with a bit of machining or shimming) then you will have to enlarge that single hole if you want maximum performance.... Plugging the bottom three holes will increase the efficiency, but you have to increase the hammer spring preload to get back the slight performance loss.... The very best combination of power and efficiency occurs with a single large hole that lines up vertically under the transfer port....

Bob