AR only fires every other shot?

[sraiford]

My wifes friend built a gun way back when she was in the Army. She asked me to sight it in and give it a run. The rifle fires about every other round, due to light strike. I used Monarch and Remington ammo, thermold, and metal mags. It really only fired when I charged it. I checked the hammer spring and it's on right. I can't figure it out.

Ideas????

 

[Jguid54]

hammer spring might be shot, try a new hammer spring, or a 5.45 hammer spring.

 

[mickey]

hammer spring might be shot, try a new hammer spring, or a 5.45 hammer spring.

or spring may be in backwards.

 

[kengel2]

Make sure the spring rest on the pin also not on the lower.

 

[sraiford]

The hammer spring is in correctly. The rubber tip on her recoil plunger was shot. I put my spare stock, spring, and plunger on it, same problem.

I should have switched uppers at the range to help troubleshoot, but didn't think about it til now.

 

[JLouv]

I'd try swapping the bolt with another rifle.

If you had the same problem, then the problem is in your lower. I'd start by changing out the hammer spring. They're cheap enough and even though it's "on right" doesn't mean it's gonna work right. Right?

If it worked with a new bolt, I'd assume it was a problem with the original bolt. I'd start by changing the firing pin.