M305 problem - Hammer intermittently fails to #### after firing

[Tengoo]

I have an M305 that I haven't shot much, and has been sitting in my lockup for a long time. In the last few days I remember why... On firing, the action cycles well enough to load a new round, but the hammer doesn't stay cocked after every few rounds...two or three shots are okay, then nothing. It seems to cycle properly by hand. Different ammo, same result.

I swapped the trigger group with another M305 and the problem followed the trigger, so I'm ruling out anything to do with the receiver or stock.

I'm going to disassemble the trigger group and make sure there's nothing in there gumming things up. Can't think of anything else to do at the moment. Perhaps there's a part that's out of spec...


Advice? Ideas? Thanks in advance...

 

[Pop]

It sounds like you're getting hammer-follow, where it's not pushing the hammer down far enough to engage the seer and so the hammer follows the bolt forward. This is a dangerous situation that could lead to the unintended discharge of the next-loaded round. It's caused by slightly too much space between the trigger group and the receiver, a.k.a. it's a stock fitment issue. The test to verify and the fix for this problem (it's very easy) is in the FAQ; essentially you shave a very (very) minute portion of the stock near the back of the trigger group cutout to fix the seating and snug it up true.

Edited to add: the hammer follow test is to cycle the action, squeeze the trigger and keep holding it down, then cycle the action vigorously five more times in quick succession, then release the trigger and squeeze it again. If the hammer doesn't fall on the second trigger pull, you've got hammer-follow. This test should be done every single time you re-assemble your rifle, or if it's ever been sitting stored for an extended length of time (especially if it's a wooden stock that can swell and contract with humidity and temperature changes).

 

[45ACPKING]

Ya Pop nailed it
probably need to gently adjust those trigger bearing points.
the only thing I could add is that it is wise to remove the material from all 3 pads so the trigger group locks in level with the action.
before you modify anything, have a good look at the areas the trigger group locks into on the stock for any proud spots or other burrs or debris that could be jammed in the trigger recess.
Also check your receiver leg that has the keyway slot that mates with the trigger group. Debris, old cosmoline , bits of stock material ect can be packed in there and not let the trigger group slide all the way in.