Weird 2 round burst issues with AR 80% lower.

[TheGaut]

I have that polymer lower I sorta practiced on last summer. Decided to put a lower parts kits in it and try it out. I know it has been milled deeper than spec by error but tought it would still work fine, at least did when "dry".

Well result, weird 2 or 3 rounds bursts.

Other thing is even when uncocked, you still can flip the safety switch which means the trigger bottom has enough play to allow it..


... anyways was surprised about the burst and kinda questioned how can this happen without an auto-sear, pocket too deep? Now don't get your panties in a bunch and go all legal reminder mode....

Thanks.

[edgerly779]

Disconnector spring upside down maybe.

[Wes C Addle]

not so much a legal reminder as a safety issue. you wouldn't want a round exploding out of battery

[protohyp]

check the sear angle and where it contacts the hammer. if either of those two are rounded or out of spec the trigger will release on reset letting the hammer fall again. try changing just the hammer out and see what happens, then the trigger and troubleshoot from there.

[Spyder]

I net edgerly is right. Upside down, or missing.

[russ69]

...I know it has been milled deeper than spec...

Probably your problem if the trigger parts are installed correctly.

[Bainter1212]

I had this problem yesterday with my new build. Using a milspec Stag LPK. Hammer/sear not in spec, hammer would fall when I reset the trigger.

You should be able to duplicate it by holding the trigger down and cycling the action.

I just went ahead and ordered an RRA two stage trigger. Should fix the issue.

[1911su16b870]

AR lower parts post assembly safety check:

1. Run/lock hammer back, verify selector will move freely from safe to fire and back.
2. With hammer back, rotate to fire, press trigger (catch hammer with other hand) and keep trigger pressed back. Hammer should fall, reset hammer with trigger pressed back and disconnector should catch hammer.
3. Slowly release trigger, hammer should be caught on sear.
4. Repeat 1 and 2. Rotate selector from fire to safe and the hammer should release from disconnector and catch on sear as selector moves to safe.

This was taught in M16 armorer school. Should be a sticky somewhere.

I have seen miss-milled trigger slots that can bind the disconnector and cause a hammer fall on release of the trigger and safety engagement/failure of the disconnector to catch the hammer.

If you've inspected your fire control components and they check OK but fail any of the above safety checks, the lower could have been damaged and out of spec. causing the unsafe conditions. (I have not yet seen a duty M16 lower so messed up that would do that, but the armorer instructor did say it can happen).

[Fantasma]

AR lower parts post assembly safety check:

1. Run/lock hammer back, verify selector will move freely from safe to fire and back.
2. With hammer back, rotate to fire, press trigger (catch hammer with other hand) and keep trigger pressed back. Hammer should fall, reset hammer with trigger pressed back and disconnector should catch hammer.
3. Slowly release trigger, hammer should be caught on sear.
4. Repeat 1 and 2. Rotate selector from fire to safe and the hammer should release from disconnector and catch on sear as selector moves to safe.

This was taught in M16 armorer school. Should be a sticky somewhere.

I have seen miss-milled trigger slots that can bind the disconnector and cause a hammer fall on release of the trigger/failure of the disconnector to catch the hammer.

Thanks

[Librarian]

Now don't get your panties in a bunch and go all legal reminder mode....

Thanks.

However, we are all confident that, now that you know it is malfunctioning, you of course have disassembled the unsafe weapon and therefore do not have an illegal full-auto gun.

[wireless]

I have that polymer lower I sorta practiced on last summer. Decided to put a lower parts kits on it and try it out. I know it has been milled deeper than spec by error but tought it would still work fine, at least did when "dry".

Well result, weird 2 or 3 rounds bursts.

Other thing is even when uncorked, you still can flip the safety switch which means the trigger bottom has enough play to allow it..


... anyways was surprised about the burst and kinda questioned how can this happen without an auto-sear, pocket too deep? Now don't get your panties in a bunch and go all legal reminder mode....

Thanks.

The rear milled "m16 style" shelf just provides room for the auto-sear to fit in the receiver. It does slightly reduce the weight as well. An "Ar15 style" shelf won't prevent a malfunction like the one you currently have.

[b1gdave32]

Like edgerly n spyder said, I had a buddy having same issues recently n the disconnecter spring was missing.

[TheGaut]

AR lower parts post assembly safety check:

1. Run/lock hammer back, verify selector will move freely from safe to fire and back.
2. With hammer back, rotate to fire, press trigger (catch hammer with other hand) and keep trigger pressed back. Hammer should fall, reset hammer with trigger pressed back and disconnector should catch hammer.
3. Slowly release trigger, hammer should be caught on sear.
4. Repeat 1 and 2. Rotate selector from fire to safe and the hammer should release from disconnector and catch on sear as selector moves to safe.

Fails 8/10.

Thanks guys, great info.

[1911su16b870]

Verify disconnector spring is installed. If yes, then I would replace trigger and try again. Inspect trigger pocket for debris, un-uniform machining etc. If still no good, replace disconnector.

[golfish]

Disconnector spring upside down maybe.

^^^ been there done that