G39 Semi problem

[Ells]

Having a few issues with my g39, every so often if I hold the trigger down in semi it'll either fire full auto till I release or fire on semi then wait about half a second to a second and then fire again and do this until i release the trigger, like a really slow full auto, or if I am lucky about 60% of the time I'll get semi auto like it should be. Full auto works fine, I am experiencing the issue both when I use green gas or propane, I also have a npas in my system and use .3 blaster BB's at the equivalent of 350fps with .2g, I have also used .25g Blaster bbs and still have the problem. I imagine the problem to be something to do with something in the trigger mech, but really not certain at all and if someone can diagnose the problem and fix would be very helpful.

[Ells]

Re: G39 Semi problem

Right, to keep this updated to anyone who has the same problem. I fortunately had access to a working G39 trigger mech (box B) and my box (box A) so here are my results. (ISA) Intermittent semi auto, sometimes full, sometimes semi). Results are for functions in semi auto.

Box A = ISA
Box B = SA
Box A + B hammer = ISA
Box B + A Hammer = ISA
Box A + B trigger = ISA
Box B + A trigger = ISA
Box A + B trigger and hammer = SA (Success)
Box B + A trigger and hammer = ISA

I also tested the firing pin base and the other bit with the spring, and completely re did this test using opposite trigger boxes just to make sure that these weren't confounding my results ( oh the scientist in me)

These results suggest that the problem lies in both the trigger and the hammer, unusual as there is significant wear on the trigger, which i thought would be the only cause of the problem. No unexpected signs of wear on the hammer in box A, however when Box B trigger put in box A with hammer A, I did notice that there was some small metal filings from where the trigger had worn, possibly from the hammer A?

If anyone is interested (probably not) I can upload some pics of my internals, hopefully this will help someone fix the same problem anyways.