[Snaps]

Now bear with me cause I don't have the first hand experience.

A friend just called me trying to figure out what is going on. He bought a Bushmaster (don't know about all the parts but the lower is bushmaster) at a gunshow this spring and shot it for the first time today. Said he took it out and it was working fine. He gave it to his younger brother to shoot and the thing just went full auto on it's own for an entire mag. Said all he did was took the Bolt carrier out, and put it back in and it was good. Towards the end of the last mag did it again, not him to his little brother again. Kid's like 15 I think, said it scared the hell out of him

Details is something I don't have but does anybody have an idea what would cause that to happen only sometimes? I could see if just started and stayed until something was changed, cleaned whatever but not just in and out.

I did a little search but I can't come up with anything. Now I'm confused... Anybody?

Thanks... Cheap fixes are best BTW :)

[Snaps]

oh yeah... if anything doesn't make much sense don't laugh at me too much. I dont' know what's going on, just stealing other people's problems:)

[Sir Galahad]

Replace fire control group. You could try to isolate exactly whch part is unserviceable, but why waste time? Just call Bushmaster and order all the fire control parts except for the safety selector. That'll be a disconnector and trigger. I don't think you'll need to replace the hammer. Bear with me, I haven't repaired a M-16A1 for over ten years. Anyway, you might as well replace the springs while you're in there. So, replace everything in there besides the hammer and safety selector. It is usually the disconnector that causes this problem. But, the best advice is to get this weapon to a GOOD gunsmith and let HIM repair it. That way, his work will be warranted.

[Snaps]

That's pretty much his plan - take it to get fixed since my theory of try something else till it works thing could get expensive after a bit.

I'm just trying ot figure out if maybe since it's probably new mix N match pieces if maybe just one thing needs fixed....

Ah well, I'll probably go look tomorrow and look for anything that just jumps out. If not take it to get fixed.

THanks for the input.

[Sir Galahad]

No, the upper receiver and bolt and carrier assy have nothing to do with this failure. The fire control parts will probably show no visible signs of the wear involved in this kind of failure. There is a function test the army uses to check these things, but I have already forgotten it. Anyway, just take the weapon to a good gunsmith who is familiar with the AR-15 and have him replace the appropriate parts. If you knew the AR, this is a repair you could do. But you're better off getting this weapon to a gunsmith for legal reasons, too. See, if you replace a part and it still fires full auto, BATFE could technically screw you for making a machine gun because you couldn't prove your repair DIDN'T cause the full auto and that it wasn't intentional. But with a receipt from a gunsmith in your hand assy group, it shows you had this failure and recognized it and took action to correct it.

[BusMaster007]

Could be the little brother secretly knows how to bump-fire...:D

Or, he found out accidentally.

Then again, having the firearm examined, and repaired if need be, would be a good idea.

[Snaps]

damn.. I never even thought of the legal part.......Since I'd probably be the one trying to monkey around with it :(

Marine Corps uses the same function test so I dunno. I really should have been an armor :mad:

[Snaps]

Bump Fire ? I doubt he actually knows how to do anything.


So maybe something that isn't going ot have to cost money to fix maybe?

[BDM]

check your fire control parts and bolt carrier to make sure the parts are not full auto ones,the notched out hammer should have caught the bottom of the carrier and prevented that,could be the surface of the hammer that makes contact with he disconector is worn or the disconector itself worn.:D

[444]

My unprofessional opinion on the function test. Run the bolt, put weapon on safe. Weapon should not fire. Switch to semi, the rifle should fire. After firing, hold the trigger to the rear while you run the bolt. Release trigger and attempt to fire. The weapon should fire. If it is full auto, it won't because the hammer will fall because the trigger is depressed. In semi, the trigger will simply reset and fire.

You can buy a complete lower reciever parts kit from Bushmaster for $64.95. Instead of trying to diagnose the problem, I would just buy and install the complete set of lower reciever parts. It is simple and can easily be done in a half hour. He will then know that everything is new, of top quality, and good to go.

http://www.bushmaster.com/shopping/lowers/alowkit.asp

Bushmaster's catalog also shows clear pictures of the difference between M16 parts and AR15 parts. ATF has ruled that any M16 parts used in your rifle, even if the rifle is not full auto, constitute a violation of the NFA. By replacing all the lower parts, you also eliminate this possiblility (other than the bolt carrier).

[Redlg155]

To be on the safe side, scrap the fire control group with a brand new one that can be trusted. A good quality Bushmaster, DPMS or Rock River lower parts kit can be obtained easily for around $60 or so from most any supplier. You will have some extra parts from the kit besides the fire control group, but spares of anything are always good to have. Installation instructions can be found over at AR15.com.

As for function checking, try this.

1. Remove the magazine and pull the charging handle back. Visually inspect the chamber and make sure it is empty.

2. Place the selector on SAFE. ( Note* The selector will not go on safe unless the hammer is cocked.)

3. With the weapon pointed in a safe direction, pull the trigger. The hammer should NOT fall.

4. Place the selector in the FIRE position. Pull the trigger. The hammer should fall.

5. Hold the trigger in the rearward position and manually pull the charging handle to the rear and release the charging handle. Release the trigger. You should hear and feel the reset (click) of the disconnector. The hammer should NOT fall.

6. Pull the trigger again. The hammer should fall.


More than likely your weapon will fail step#5 when you release the trigger from holding it back while charging it.

Good Shooting
Red

[Snaps]

I'm going to have to try and remember all this for tomorrow:uhoh:

[gun-fucious]

it sounds like someone was filing a custom trigger job and went a bit to far

[444]

Snaps, if you have never assembled or replaced the parts in an AR15 lower reciever, here is everything you need to know. http://www.ar15.com/content/docs/assembly/lower/
The first time I did it, I sat my laptop on the bench and followed the instructions. It is so easy, that the next however many I built didn't require instruction.

This description of the function check might be more clear than the dribble I pass out: http://www.ar15.com/content/docs/functionCheck/


In reality, there is nothing to remember, tell him to buy a new lower parts kit and install it. If it was mine, I would immediately remove all the parts from the lower reciever and toss them in the lake. Who knows what the last owner did, and he doesn't want to get busted for something that he didn't even have knowlege of.

By the way, that first link about assembly of the lower reciever also clearly shows what the parts are supposed to look like for a legal, non-NFA rifle.

[Steve in PA]

A few weeks ago I attended an NRA LEO Patrol Rifle Instructor Course and we were zeroing our rifles. I was teamed up with another shooter who was using a Rock River AR and while shooting single rounds from the prone he had his rifle go full-auto. We thought perhaps he flipped the selector switch, however......he did not have full-auto on his rifle!!!

We broke the weapon down, thinking that maybe the sear and other parts were worn, but they didn't look like they were. And the rifle never went full-auto again during the week. My guess is the parts were worn just enough for it to happen and I would, like he will be doing, replace the parts.

[JShirley]

Not discounting other good advice here, but it's interesting this only happened to the son. Check to be sure he isn't holding the weapon loosely, and his finger stiffly (if that makes sense).

John

[AR-15Nutt]

there is a parts ID section at ARFCOM..., check your parts for possible M16 parts..., i once bought an AR-15, it had the habit of going full auto on occasion, i checked out the fire control parts & lo & behold the only legal part in that rifle was the selector !!!! i imediately took every illegal part out & threw them away !! spent over $250 to make that gun legal......

one more reason to know what to look for & thuroghly check out what you are buying........:D

[Chipperman]

Isn't it hard to bump-fire an AR, even intentionally?

[Snaps]

Well thanks for the advice folks. I checked it out today. Took it to the range and it worked fine.:confused: Anyway under fear of getting picked up for it he's gonna get on the net today at some point and order the whole setup from the lower adn I'l lswitch it out for him when it comes in.


Thanks again y'all.

[Bart Noir]

Galahad, Sir, you have been reading too many Field Manuals.

Bart Noir