Update:

Fired the pistol down in Texas to the tune of about three hundred rounds.

Between the new bolt carrier (not bolt carrier group, just bolt carrier), the spring-loaded firing pin, and removing the black rubber stud from underneath the extractor, it works...til about the three hundred round mark.

At the three hundred round mark, I had one or two of a similar failure to eject - the rounds make it out of the chamber, but not out of the receiver.

She'll get another detailed cleaning and probably another two hundred rounds. I don't want to strip all the accessories off and send her back to the mothership but I might have to at this point. The gun's definitely a keeper and I'm probably going to add a spare to the list, it's that much fun - but this FTE stuff isn't gonna fly.

Another update -

Took it to the range and had about five FTEs out of 300 rounds fired. Breaking in the pistol does seem to have cleared up the issue of the pistol not going into battery, but that's about five times too many FTEs on a clean weapon using quality commercial ammo (Win NATO 9mm). Hell, I had an FTE on THE VERY FIRST ROUND FIRED of the day.

This little piggy is going back to SIG. I may - MAY - number my magazines and take it out for one more rodeo after a cleaning, but I'm having a hard time imagining a scenario where the FTE was caused by a magazine (FTF jams would be a different story).

Ya' my money is that the mags are irrelevant. Back to the glue factory if it were mine.

I was having failures to eject with my gen 2 MPX as well. It eventually broke the tip of the firing pin off indicating that the firing pin was sticking our of the bolt face while the the cartridge was trying to be ejected out.

I called SIG and told them what happened and they sent me a package of replacement parts. Basically the same parts as with the MCX recall. I received a new bolt carrier, firing pin with a firing pin spring. After moving the bolt and whatever that part that part is called that's like the bolt carrier key on an AR to the new parts it has ran like a champ ever since.

So,instead of the firing pin free floating it now has some spring pressure pushing it back into the bolt.

quote:

Originally posted by John3200:
I was having failures to eject with my gen 2 MPX as well. It eventually broke the tip of the firing pin off indicating that the firing pin was sticking our of the bolt face while the the cartridge was trying to be ejected out.

I called SIG and told them what happened and they sent me a package of replacement parts. Basically the same parts as with the MCX recall. I received a new bolt carrier, firing pin with a firing pin spring. After moving the bolt and whatever that part that part is called that's like the bolt carrier key on an AR to the new parts it has ran like a champ ever since.

So,instead of the firing pin free floating it now has some spring pressure pushing it back into the bolt.

SIG sent me the same parts...this, combined with playing with the extractor spring, fixed the failures to go into battery. Sadly, it seems to have reduced, not eliminated, my FTEs.

SIG sent me an RMA so I will have the gun boxed up and out the door via Fedex by Friday.

Not much to add here except that mine did take several hundred rounds to break in. But I didn't have near the trouble you are during break in.

I have a Franklin binary trigger in it now, runs perfect.

My unmodified MPX had a tendency to go full auto. I replaced the trigger and it’s been fine. Have to say it’s a little scary when it would let go. It wasn’t that I couldn’t handle the gun (I have a transferable smg) I was just always worried the wrong guy would see it shoot like that and take me in for having an unlicensed machine gun.