AR help.

[Deadeye 325]

I am not an AR guy. My friend has a ar that has a problem. It fires in random burst sometimes. and then ftfs sometimes the shells that dont fire have a light dimple in the primer please help me help him.

[ShadowFire 220]

It's Slamfire

 

First, check your firing pin. Original firing pins for civilian ARs were first made of steel. It was free float, same as the M16s of their time. It created slam fires because the extra mass the steel had, ignited commercial primers. Later, they went to titanium firing pins to solve the problem. Now, even M16s and M4s have titanium firing pins. Less mass = less energy to dispurse on contact.

 

If it's the firing pin, a Titanium firing pin will likely solve it. You'll still have a dimple sometimes but it should never be anything to worry about. If you still have issues, it might be a bolt out of spec. Too deep, it might aid in it igniting the primer, causing slamfires. Too shallow, it won't punch the primer at all. You need it just right.

 

Your FTF might means that your friend prolly runs a standard civilian buffer made for semi auto ARs. It was not designed to provide your rifle with enough force to load each round that fast. That is why the M4s use the H2 buffer. So far as I know, there is nothing wrong with using an H2 buffer in a Semi-Auto only AR, it just provides a lil more force to each round being loaded, that's it. I just don't use one, personal preference.

Edited January 15, 2012 by ShadowFire

[JoshAston 39]

AR15/M16 firing pins are not titanium. Yes there are titanium ones available, but they're not standard issue. Competition thing only, titanium is too brittle to be used in a combat gun.

 

The light dimple on the primer is normal on any gun that has a floating firing pin, which includes the AR.

 

The bursts and failures to fire are both being caused by hammer follow. The fire control group either needs to be installed correctly or replaced if it's defective. Do a function check. Pull the charging handle back, release. Pull the trigger and hold to the rear. Charge the weapon again. Release the trigger, you should hear a click. If you don't, the disconnector is defective. First thing to check with the disconnector is to see if it's properly installed. The large end of the spring should be down, seated in the trigger. If it's not, it will cause the problems your friend's having. Flip it over and make sure the large end is fully seated in the trigger, that will solve the problems. If that's not it, replace the fire control group, because one of the parts is defective.

 

ETA: Hammer follow means that the disconnector isn't catching the hammer and holding it back so that the sear can grab it when you release the trigger. Sometimes the hammer will drop at just the right moment so that it has enough force to pop the primer. Other times it will literally follow the bolt carrier, not having enough momentum to pop the primer. This will give you bursts and failures to fire. I'd be willing to bet that the disconnector spring is either broken or upside down. If one of the parts was actually defective, the bursts/failures would be more consistent.

Edited January 15, 2012 by JoshAston

[Deadeye 325]

thanks for the info I will look at it and try to fet pictures

[kevin.rose0@gmail.com 62]

BTW, people have GONE TO JAIL over this. Do not screw around with it. It needs to be fixed right now.

 

http://en.wikipedia.org/wiki/David_Olofson

[Scott Kenny 144]

It doesn't help Mr. Olofson's case that the other dude said in testimony that

Kiernicki testified that Olofson had told Kiernicki that the third position of the rifle's firing selector was for automatic firing, but it jammed, court records indicate. He also testified Olofson told him he had fired the weapon on the automatic setting at that same range without a problem.^[3] According to Len Savage, a weaponry expert who runs Historic Arms LLC, BATFE paid Kiernicki an undisclosed amount of money for his testimony.^[4]

 

Pardon the wiki copy/paste. The nasty point there is that according to the other guy, Mr. Olofson had an automatic weapon and HADN'T FIXED IT.

 

I will bet you large dollars and my personal firearms collection (and further purchasing ability) that if Mr. Olofson had stopped as soon as the thing doubled, and went looking for parts to fix it, there wouldn't have been a problem from ATF.

 

If he had told Kiernicki "that weapon is having a dangerous malfunction and needs to be fixed. NOW," then even if Kiernicki had gone to the ATF, it would not have gotten as far (especially if there was a gunsmith's testimony involved that this was a malfunction, not a modification)

 

But your friend needs to fix this ASAP.

[kevin.rose0@gmail.com 62]

The ATF has also had people testify that a 14" shoelace is a machinegun. The difference is that the ATF didn't get away with the shoelace. It's just not worth screwing with it. A successful defense will likely ruin you financially, otherwise you are financially ruined, in jail, can never posses a gun again and will have a hell of a hard time getting a decent job again when you get out.

[redfish28 50]

I had this same problem. Replace fcg. Also make sure the trigger pins are not walking out. This was the cause of my problem.