disclaimer: I heard this in conversation, I do not know the person, or weapon in question, so don't ask!

The other day, I heard a guy talking about his "AR" and how he built it from a DPMS lower and kit he bought, and how sometimes it shoots 2 shots in a row with only one trigger pull. He stated that it was a new DPMS kit and nothing was "worn" or "used".

WTF? How could this be?

Any input, thoughts, etc? I'm looking at building a DPMS lower and would like to order one of their kits, but I don't need the damn thing to shoot twice!

It's doubling & it's a dangerous situation. He or somebody more competant needs to re-examine the rifle.

Yes he needs to get it looked at.

He has a problem with the disconnector.  His disconnector either is not catching the hammer or is releasing it early before the trigger is in position to catch it.  I can be nothing else.

I've had that happen when shooting for accuracy with my FAL... the way I was holding the gun just lead to the occaisional bump firing of 2 rounds instead of one.  Nothing wrong with the gun, just the way I was shooting.

It's easily done ColtCarbine, "new" does not mean "proper".

Weird, must be a fluke.  I had a DPMS and the fire control parts were nicer than my RRA parts.

We don't know where he got the "kit" he bought, and we don't know whether hw assembled it properly either, so anything is possible here.

Suffice it to say that the man has an improperly functioning rifle.  To me, this is the down side of the "build it yourself" movement.  Too many people are building up ARs (and AKs too)without really understanding what they're doing, how to check for proper function before they get to the range, and what to look for in the parts they buy.

On the other side, too many distributors are buying parts and assemblies from subcontractors who do no inspection and guaging of what they're shipping, and it becomes the purchaser's job to be the parts inspector.

It's not just the marginal outfits either.  In the past couple of years I've gotten out of spec, and even broken parts from Rock River, DPMS, and Bushmaster.  It's gotten to the point where I'd rather buy used GI surplus parts at the gun show, than new commercial stuff.

All the big outfits are doing a fine job with uppers, lowers, and barrels these days. Just wish the small stuff was always of equal quality.

I agree with what was posted in that there really is two possibilities that are most likely...

1.  Bump Firing, especially if anything was done to lower the trigger weight or the trigger weight is pretty low.  

2.  The disconnect could be suspect but if this is a problem you would expect to get a few failure to fires as well from the hammer dropping out of battery.  Note, this is the scarrier of the two possibilities as without timing there is a risk of a KABOOM.

What I would do is cycle the weapon EMPTY with your finger keeping the trigger depressed and when the carrier is forward release the trigger and see if the disconect releases the trigger allowing you to dry fire...  If the hammer is dropped already, then it is a disconnect problem and it is not safe to shoot.

As for testing the bump fire, this is tougher as we have seen people claim it wasn't their fault inthe past because they have shot for "hundreds" of years and it must be the gun...  If this person has this attitude, well you may never be able to find the solution so replacing the disconect is a cheap and safer precaution.

I would have ZERO wories about this happening with a DPMS kit and putting your lower together is so easy that I think I could have my 6-year old do one [thinking] and unless you are quite mechanically un-inclinned I would build your own just for the knowledge you will gain!

Good Luck!
QB

[white]sssshhhhhhhhh, that's the new "burst" feature. Don't tell anybody. [/white]

I've always said that the greatest failing of the AR15 is that any chimp can screw one together. [:(]

If the rifle is doubling only occasionally the rear of the hammer may be hitting the top rear of the disco so hard that it keeps the disco from snapping forward fast enough to grab the hammer on the hammer's return stroke.

If it doubles predictably then usually there isn't enough disconnector engagement or the trigger is short. Could also be the synergy of many slightly wrong factors.

First check is to pull the trigger then cock the hammer onto the disconnector. Holding your finger so that the hammer can't hit the lower without touching the hammer, very slowly release the trigger. The hammer should not drop to its fully forward position. Repeat this check several times.

If the FCG passes that check then let the trigger go forward and slowly cock the hammer by hand . The hook of the disco should ALMOST touch the middle hammer hook.

If that looks good then pull the trigger and cock the hammer and push down on it as hard as you can. Does the hook of the disco rock completely out of engagement with the middle hammer hook or is there still a slight overlap?

If there is still a slight overlap get a no mar mallet, hold the trigger to the rear and cock the hammer onto the disco. Tap the face of the hammer with the mallet with a glancing front to back strike. Repeat several times, the hammer should not fall.

That’s not really that unusual if you’ve built an AR by yourself.

My first AR was a Pre-Ban Bushy.  It was bought 2nd hand.  I often got two shots with one trigger pull.  Sometimes I would get [b]Three![/b]
I took it to a [i]Good[/i] Gunsmith.  He replaced the trigger and I think the disconnecter as well.  He also tightened up the gas tube as well as a few other things.
He told me the previous owner had probably built the gun from scratch.  While he did an OK, job on it, it wasn’t as good as it Should have been.

If the trigger pull is under 4.5 lbs, it could cause the doubling.  Measure the pull weight.  Unfortunately, aside from measuring the trigger weight, there is no other way to determine if the trigger is too light other than firing it and letting the natural cycle determine if the trigger is too light.  Cycling it by hand does not have the same effect as the recoil / gas charging system.
In many cases, if the trigger is too light you will end up with a slam fire or light primer strike that will not pop the primer, leaving it in an un-charged state.