I bought a "converted by bill fleming" Colt Sp1 Reg Receiver recently.  Form 4 came through and I took possession on Sunday evening.

It has a Tapco 4 position FCG in it.

I took it out today to test it out.  Mated it with the upper from my Factory LMT MRP Piston 12" SBR.

Fired great in Semi.  Safe works too :)

Auto fires a single shot, and then the trigger doesn't reset.  If I put the selector on Safe (I can hear the trigger reset) and then back to Auto, and pull the trigger again, it fires another single shot.  Rinse and Repeat.

Same with Burst.

It had the same problem with or without the suppressor on it.

Possible solutions?

1)  How do I tell that my LMT 12" upper has a full auto bolt?  I was told that it does when I bought it but never verified as this is my first M16 out of the Corp... and it is a piston upper to boot so I am even less experienced there.

2)  What could be wrong with the lower, if anything?

3)  the upper and lower are an EXTREMELY tight fit.  I have to put in the front take down pin and then push the lower down in the back hard and then push the rea take down pin in.

I have no other uppers with full auto bolts.

The Upper works fine for several hundred rounds through it on the Factory SBR lower from LMT.

Thanks in advance for your assistance.

Semper Fidelis,

Kent

Notice the cutaway on left side of the top carrier?  That one is a semi carrier.  The bottom is auto.

PossumKing... thanks.

What about one that seems to be in the middle of the two? :)



There is the actual BCG... uncleaned from the one mag I put through it trying to get it to function (only semi).

Semper Fidelis,

Kent

The pic you provided is a semi-auto bolt carrier. It is shrouded in the firing pin area like an M16 carrier, but the portion at that rear that trips the auto sear has been milled back to semi-auto configuration.

I'd imagine that could effect its ability to go full auto :)

I swear it was supposed to be a full-auto carrier when I bought the gun.

Anybody got a full auto carrier that will work in the LMT MRP Piston guns they want to sell for cheap? :)  or even a fair price if not cheap? :)  Or maybe wants a lightly used semi carrier :)

Semper Fidelis,

Kent

Funny you should ask.  The carrier in the middle is an SP1 carrier.

I hope you get a bolt soon, I have a Fleming SP1 also and it runs great.

  Because it's a one piece bolt carrier I would suggest you get on the horn to LMT and arrange for a swap.   short of that

I did call LMT, and have already sent the semi bolt carrier back.  They verified my Form 4 and are swapping it for a full auto one.

Thanks :)

Semper Fidelis,

Kent

Make sure you don't have the selector in the auto position when assembling the upper & lower or the sear will be in the way. I assume you're using an offset front pin to mate the large hole lower to a small hole upper. I find it easier to engage the rear pin first then work/rotate the front pin into place.