M&P 15 troubles

Killer66 · Jan 31, 2012

Hey fellas~
I have just moved back up here from Texas and I bought an AR15 while I was down there. It was used and I was really excited to fire it when I got here. I went out to fire it and it would not fire the Federal .223 rounds I put in it. It would just dimple the primer. I put a new spring in it and now it will fire a couple rounds and after about three rounds it will not extract the shells from the barrel. Have any of you had troubles like this before? My buddy in Texas thought maybe the fella before me had used steel Wolf ammo and the lacquer on the outside of the shells had transferred to my barrel and then when I heated the barrel up the brass shells would stick??? does that sound at all reasonable? Give me some ideas, thanks!

doubletap007 · Jan 31, 2012

dirty gas block?if the hole is plugged it wont cycle properly and may be why it wont eject the casings.
as for weak firing pin dent,did you clean the bolt real good?maybe plugged f/p hole also?
you mentioned changing the spring....a firing pin spring?because i dont know of an ar15 with a spring on the firing pin.
maybe the spring is not supposed to be there at all?i dont know the m&p rifle at all but i have never seen a spring on the firing pin of an ar15....an ar10 yes but not ar15.

iamme · Jan 31, 2012

I'd try replacing the extractor spring and hammer springs. While at it grab a new FP as well just to make sure that one's not messed up.

mkwerx · Jan 31, 2012

Been a while since Wolf was lacquer cased, for years it's been coated in polymer that doesn't melt like the old red, gooey lacquer did. It's *possible* they shot the old stuff. Scrub the crap out of the chamber with a brass brush and good solvent. Scrub the crap out of the whole gun, honestly.

One problem you can run into shooting the modern Wolf ammo, is that steel doesn't expand the same way that brass does when fired. You get a bit more gas blowback into the chamber. If you switch from the Wolf steel cased ammo to brass ammo, its possible the brass can get stuck if there's a lot of carbon build up. Easy fix - just swab out the chamber, or run your bore snake down it once before shooting brass after shooting steel case ammo.

have you tried other rounds than the Federal stuff?

Buddhalux · Jan 31, 2012

Check your gas key on top of your bolt and make sure that it's staked properly (tight and in the correct position).

coop44 · Jan 31, 2012

.223 is a "reduced load" for a gun built for .556. try military type loads,
check chamber- may be rough if brass is frosted,
check entire gas system for fouling, get some long pipe cleaners for the gas tube. blow it out with compressed air, both ways.
hammer spring- change it out- make sure it is correctly installed!!
extractor spring-change it out

I'll think of some more but that's a start

Eric911 · Feb 4, 2012

I went out to fire it and it would not fire the Federal .223 rounds I put in it. It would just dimple the primer.

Light primer strikes are often cause by an improperly installed hammer spring. Refer to the photo below. Note how the spring legs come from underneath and rest on the top of the trigger pin. If the hammer spring is installed backwards, minimal spring pressure is applied to the hammer, resulting in light strikes. Correctly manufactured hammer springs don't wear out very often.

after about three rounds it will not extract the shells from the barrel.

Good info posted already on this. Soak the chamber/barrel extension with solvent and scrub the heck out of it with a chamber brush. Field strip the bolt. Clean and inspect the extractor. Be sure that the extractor lip isn't rounded off or chipped. Be sure that your running a decent extractor spring with adequate tension, especially if used in a carbine. Some additional info here.

biggie24420 · Feb 5, 2012

What is the best way to clean out the gas block and the gas tube on a DI AR? I figured maybe spray cleaner and use a pipe cleaner?

TX.

Eric911 · Feb 5, 2012

Even though I despise the term, the gas tube and gas port are essentially self cleaning. Running at about 50K psi, it does not easily clog. More problems are created by stuffing things in the tube and getting them stuck. Some folks like to blast non-chlorinated brake cleaner down the tube, but there isn't any prescribed PM. If the tube does become clogged, the part is just swapped out.

madcratebuilder · Feb 5, 2012

biggie24420 said:
What is the best way to clean out the gas block and the gas tube on a DI AR? I figured maybe spray cleaner and use a pipe cleaner?

TX.

Just say no to the pipe cleaner. Spray it out with some carb clean. Don't get the carb clean on any plastic parts. Only time I've seen a gas tube that needed cleaning was after a few thousand rounds of .22lr. With 5.56 it's self cleaning.

To the OP. The Fed .223 is low power ammo. Get some XM193 to test this weapon. First fire one or two rounds from the rifle and see if the bolt locks back after the last round. If it does then the gas system is working. If it still has FTE then a extractor cleaning, new spring, insert and even add a O ring or D ring.

99% or all AR problems can be fixed with MEAL.

Mags
Extractor
Ammo
Lube

Buddhalux · Feb 5, 2012

They do have pipe cleaners that were made for the AR gas system.

joeroket · Feb 7, 2012

Eric911 said:
Light primer strikes are often cause by an improperly installed hammer spring. Refer to the photo below. Note how the spring legs come from underneath and rest on the top of the trigger pin. If the hammer spring is installed backwards, minimal spring pressure is applied to the hammer, resulting in light strikes. Correctly manufactured hammer springs don't wear out very often.

Good info posted already on this. Soak the chamber/barrel extension with solvent and scrub the heck out of it with a chamber brush. Field strip the bolt. Clean and inspect the extractor. Be sure that the extractor lip isn't rounded off or chipped. Be sure that your running a decent extractor spring with adequate tension, especially if used in a carbine. Some additional info here.