Issue with semi-auto function (M10)

[Homemadeammo42]

Finally got to take out my new-to-me M10. Had a fantastic experience. However, my semi-auto function did not work properly. I function checked prior to the range and it seemed fine. At the range with semi-auto selected, it would fire a burst, then the disconnector would trip and it would revert to semi auto for a bit. I just wanted to zero my optic on my Lage. In full auto, it functioned as it should. Brought it home and cleaned it. Function check now shows semi-auto not working at all. I also noticed the selector switch is backing out a little.

Are there any quick fixes? Any parts the commonly wear down that I can replace? Any advice is welcome. This is my first experience with a M10 so any knowledge is welcome.

 

[xdamagedx]

easiest fix is to put 1 bullet in a mag. Next might be the trigger spring (which also pushes the semi disconnector).

 

[Homemadeammo42]

I ended up doing one round per mag to zero. I still would like full function of my MAC.

 

[Manthony]

I ended up doing one round per mag to zero. I still would like full function of my MAC.

Is your MAC missing the retaining wire? If not, is it seated correctly in the channel of the selector? This is not my photo, but it shows the silver colored wire.

 

[A&S Conversions]

I ended up doing one round per mag to zero. I still would like full function of my MAC.

Certainly, your gun, your choice, but for me I installed the Practical Solutions "Eliminator" sear shaft to eliminate the semi auto function. Personally, I bought my machineguns to shoot as a machinegun. YMMV.

Scott

 

[m11stuff@hotmail.com]

Finally got to take out my new-to-me M10. Had a fantastic experience. However, my semi-auto function did not work properly. I function checked prior to the range and it seemed fine. At the range with semi-auto selected, it would fire a burst, then the disconnector would trip and it would revert to semi auto for a bit. I just wanted to zero my optic on my Lage. In full auto, it functioned as it should. Brought it home and cleaned it. Function check now shows semi-auto not working at all. I also noticed the selector switch is backing out a little.

Are there any quick fixes? Any parts the commonly wear down that I can replace? Any advice is welcome. This is my first experience with a M10 so any knowledge is welcome.

What ammo are you using? An under powered round can cause the gun to short stroke and not catch the sear. We recommend 230 gr full metal jacket ammunition for the MAX-10/45.

 

[Homemadeammo42]

Is your MAC missing the retaining wire? If not, is it seated correctly in the channel of the selector? This is not my photo, but it shows the silver colored wire.

I have the retaining wire and its seated correctly compared to the photo.

I think the issue is this piece that I circled. The piece below it slips off when I push down on the nub that the bolt would hit. https://imgur.com/a/djQFGUm

 

[Homemadeammo42]

What ammo are you using? An under powered round can cause the gun to short stroke and not catch the sear. We recommend 230 gr full metal jacket ammunition for the MAX-10/45.

Thanks for the reply Richard. I dont think this is an issue with your upper at all since its not passing a function check even with the stock upper. I was shooting Wolf 115. On full auto, both uppers functioned flawlessly. I think the culprit is whatever part I circled in red is. The arm under it keeps slipping off instead of pushing up, resetting the trigger. https://imgur.com/a/djQFGUm

 

[DINK]

There's a "leg" on the right side of the trigger spring that sticks straight up and it's supposed to be behind the disconnector (the part you circled), pushing the disconnector forward so it engages the sear. If that leg on the spring is weak, bent to the rear, or missing, the disconnector will fall off the sear and you will get unscheduled semi-auto. The disconnector is supposed to stay on the sear unless it is pushed to the rear by the trip, which is either raised up to contact the underside of the bolt (with selector set to "semi") or lowered down to not contact the bolt as it goes back and forth ("full auto").

Check the disconnector to see if it's being pushed forward properly. You might be able to bend the spring forward to put more pressure on it or you may wind up with a new spring. I have also fixed functioning of these parts by replacing the pin that the disconnector is held by. It was undersized and the disconnector was able to flop around. Under recoil, it would disconnect when it wasn't supposed to.

 

[Manthony]

I have the retaining wire and its seated correctly compared to the photo.

I think the issue is this piece that I circled. The piece below it slips off when I push down on the nub that the bolt would hit. https://imgur.com/a/djQFGUm

I agree with DINK. From what you describe it sounds like an issue with either the trigger spring or a loose selector. You mentioned earlier that the selector was walking out, check to make sure the hole on the receiver is not egged out or the selector is not out of spec.

 

[Homemadeammo42]

I agree with DINK. From what you describe it sounds like an issue with either the trigger spring or a loose selector. You mentioned earlier that the selector was walking out, check to make sure the hole on the receiver is not egged out or the selector is not out of spec.

I think either the selector is out of spec or the spring that holds the pins in is weak. I bought a new spring since thats the cheaper fix. If that doesnt work, Id wager the selector is out of spec. I dont think it has anything specifically to do with the disconnector. Sounds like if that was an issue, Id be getting semi auto when I want full. I have the opposite issue.

 

[DINK]

Your selector has two flats on it and the pressure from the retainer spring is the only thing that holds it in either the "semi" or "full" positions. If the retainer spring is weak, not only will the selector start walking out of the gun, but it will rotate when you are firing, so you will get unreliable selection of fire modes. Also lube the selector where the sear rides on it so there's less friction to cause it to rotate along with the sear.

The selector functions as a way to raise and lower the trip so it either contacts the underside of the bolt or does not. You will note that the part of the selector that the trip rides on is cut as an eccentric cam and that's what raises or lowers the trip. Sometimes the trip is a bit too short or long and it contacts (or fails to contact) the underside of the bolt when it's supposed to and it needs to be adjusted a bit. The selector itself is probably just fine.