I have used the prod trigger group on 2240 and 1322. It is a bolt-on - well mostly. On the 2240 and 1377 I used solid hammers by http://yeoleairgunshop.yolasite.com/. Excellent workmanship. I'm not going to get into light-hammer heavy-hammer and light-spring heavy-spring.On the 2240 it was 100% bolt-on - exact replacement - same grips. On the 1377 I had problems, and could not get it to cock, until I posted and read information on CAPOF. Seems the prod sear interferes with the air tube on some guns. The fix is enlarge the air tube sear slot toward the front about a 1/4" or so. An easier solution is to grind the top, forward portion of the prod sear about 1/4" so that it does not contact the air tube.I will try to find the CAPOF information.