Fire Selector Switch Help

[Ross9632]

hi there, I'm needing some help with my G&P M4 Sentry. The fire sector switch moves freely between safe/semi/auto. 

 

Safe works fine

Semi works fine

 

When switching to auto the trigger seems to only pull 3/4 of the way back and has no firing action.

 

Does anyone know what this could be and how to fix? 

 

Thanks 

[Sitting Duck]

first guess is a cracked selector plate, right at the arch...

 

 

if it is cracked then when selector switch attempts to move to Auto

it will not pull the plate to shift it properly to full Auto position

(basically fully lifting the Cut Off Lever upwards 101%)

 

Sounds like the COL is not raised fully so trigger trolley is hitting the COL

than slip under/over it

Though I would have thought the trigger would only pull say 30% of travel before hitting the trolley/COL

 

Could be trigger contacts impeding the trolley, but initial thoughts are selector plate

 

Did you remove box recently, usually plates can break when refitting box into receiver

than break on there own

Though a stiff selector or stiff plate, catching rather than moving freely can wear/break if forced

or also if gun is abused or dropped - stuff happens

 

but broken/cracked selector plate is my first guess

If you do replace a faulty plate, ensure you make close comparisons between old/new

some plates, the arch appears in a slightly different place which if not checked can also create issues

where the COL is not fully raised/lowered or safety doesn't fully operate properly in all 3 positions

Usually they are fairly compatible, but they can/do vary if you replace genuine parts with aftermarket ones

 

if semi is working correctly, then trigger trolley and trolley stop pin is all intact

so this would likely point to cracked selector not fully raising the COL for AUTO to function correctly

reckon cracked at arch, then it doesn't shift the whole plate as it moves back so COL not raised on Auto...

 

 

It isn't an ambi fire switch is it ???

don't think so, but just checking in case other selector switch has gone tits up on other side

and impeding the movement  on other side/plate shifting selector plate to auto properly

(doubt it, but there is some reason why plate isn't operating properly to move to Auto)