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 Bushmaster XM15 failure to lock open after last round
topgun44  [Member]
1/17/2012 6:37:49 PM EDT
I purchased a new BM XM15 E2S. When the gun heats up after about 75 rounds I have some double feeds and eventually the bolt fails to lock open after the last round every time. This happens with the factory mags as well as with all 6 of my magpul mags using winchester factory ammo. The gun has been back to BM under warranty and they replaced the upper saying that the gas port tollerences were off. Once I received the gun back with the new upper (original bolt carrier group) does the same thing once it is heated up. The gun is sent back again to BM. BM has been great to deal with and say they will replace the gun if it is not corrected. Any suggestions, A friend of mine has the same gun and it is having the same problem....just seems a little too much of a coincidence........are there issues with BM right now??

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wildearp  [Team Member]
1/17/2012 6:46:49 PM EDT
What specific type of Winchester factory ammo? Try different milspec ammo before wasting a minute more of your time on this.

My bushwackers ran fine on everything, even Wolf, until they started seizing in the chamber. Lesson learned.
topgun44  [Member]
1/17/2012 6:49:10 PM EDT
Winchester 55 gr white box
topgun44  [Member]
1/18/2012 1:05:53 PM EDT
I hope it is as simple as using cheap winchester ammo. Just a bit skeptical because it works fine when the gun is cold. Once it is heated up the bolt fails to lock open on last round.......on both uppers from BM.
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Dano523  [Moderator]
1/19/2012 6:14:05 AM EDT
Check the key allen bolts to make sure that they are 37in lbs tight.

If you get any allen bolt movements before that amount of torque, get the manufacturer on the phone for a B/C replacement.

As for if you find the the allen bolts are not correctly torqued and you want to fix the problem yourself, then throw the old bolts away, lap the key to the carrier, then install new bolts, then stake the key metal to the side spines of the new bolts.

Also, Not sure if this is your first rodeo with the platform, but Hoppes solvent and #9 oil is not the correct solvents to use. Bore gets cleaned with something like sweets that does not leave a residue behind, chamber gets cleaned with a chamber brush by hand and CLP, the rest of the rifle cleaned with CLP, then the upper bearings areas (including inside the B/C as well) lubed with CLP on the wetter side for break in.

I guess that the Key has some problems and as the steel heats up, your getting a gas leak, but if you are using Hoppes products, as the cleaning solvent residue heats up, it can cause some problem as well in the chamber. And #9 oil, has no cleaning agents in it, so does not prevent fouling from building up either.

Bottom line, CLP (BreakfreeCLP if you need a civilian source) has a cleaning agent in it, and regards to lube, the teflon in it does such long after any liquid lube portion of the mix has long burnt off

topgun44  [Member]
1/19/2012 9:33:14 AM EDT
This is my first AR. I use breakfree CLP and I keep the bolt wet.
The gun is with BM now.

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