M16 with light primer strikes. need help

I have this posted on my HTF forum as well.

First..I'm an 07/02 so please no, "IT'S ILLEGAL!" in the thread please.

I need some guidance as I am at my wits end. I milled a Spikes AR-15 to accept the M-16 FCG. Used Bowers jig for auto sear pin hole. Once complete, I took it outside to test fire and was rewarded with flawless semi auto performance. Flipped to full and fired 3-4 rounds then misfire. I cycled the action and the round pops out with a light primer strike. Fired another 3-4 rounds and jammed. Over and over.

I though bolt bounce...

Remedies tried:

Colt 9mm two piece buffer.
Colt standard carbine buffer.
Spikes H2 buffer....works best, may get 6-9 rounds before misfire.
Spikes H3 buffer....fires one round, click, cycle...fires one round then click, cycle then two round then click...

Operates best with H2 buffer. Sucks with H3.

Set up is a factory 10.5" LMT upper, M-16 carrier, Spikes lower. I'm shooting suppressed with an AAC 7.62SD to keep the neighbors happy.

Ideas????

What kind of ammo were you running?
Have you tried it with any other upper or just the 10.5"?

When it jambs....is there a live round in the chamber and hammer forward as if it tried to fire? You then eject the chambered round with the light primer strike?

Trying to picture the failure.

Your answer on timing the sear may be here:
http://www.ar15.com/archive/topic.html?b=6&f=23&t=318446

Maybe a Wolff extra power hammer spring would help. Without knowing much else about the malfunction I would try that in combination with different buffer springs and buffer weights.

He has tried different buffers in hopes it may have been a bolt bounce issue.

I vote that the auto sear is not timed correct and is releasing the hammer too soon. Hammer is falling prior to bolt being locked up in barrel.

Also check your autosear engagement with the hammer. When mine was doing this the sear wasn't engaging the hammer enough causing it to follow with the recoil of the gun. Mine was a out of spec hammer. I could use my finger and pull the hammer off the sear.

Make sure you milled the LH side of the receiver back far enough and low enough for autosear clearance. If not, the leg on the autosear will stick rearward and won't reset to catch the hammer. Because the selector is in "auto" while trigger is pulled, the disconnector will also not catch the hammer. The hammer then follows the bolt closed and won't hit the primer hard enough to make it go bang.

I had this exact same problem with two separate lowers I did last week. A few more minutes in the milling machine and they ran like a sewing machine.

Make sure the receiver is milled wide enough that the sear doesn't bind. (pinch)

Also... and this isn't a common problem... make sure the sear doesn't contact the upper when closed. Some uppers don't have the sear cut in them and the sear will get pinched when you close it up.

Do you have the autosear spring in front of the selector lever ?

Dragracer_Art had the answer. Additional lower material needed to be removed to allow the auto sear to catch the hammer.

Runs flawless now.

Thanks for the update! Its good to know.

Outstanding !

Now go build some more before the Zombies attack !

Light hammer strike?

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