Walking hammer pin issue with Bushmaster AR.

[og556]

So far I have about 500 rounds through my Bushmaster M4A3 which I purchased about a month ago. Today I noticed something strange about the hammer pin. It seems as though it is sticking out a little bit on the right side (ejection port side). I pushed it back in and then dry fired a few times to see if it would happen again. Sure enough it started walking again. It does not fall out or go past the depth of 1.5 - 2mm.

I stripped the rifle and looked at lower receiver springs to make sure every thing was assembled correctly and it looks as though it was from the pictures I could find on here. I went ahead and took a small punch to see if I could move it a little bit with the hammer not cocked and it will move but not past 1.5-2mm.

What should I do from here ? Is it normal for the hammer pin to move a little bit out of the gun or is this something out of spec ?

When I cock the hammer the pin is locked in place and can not be moved at all.

[toddackerman]

This happens occaisionally. Those who have "Trigger Pins" walking many times don't have the trigger group assembled properly with the left leg of the hammer spring on top of the trigger pin in the groove that keeps the trigger pin from shifting.

But..as in your case, the Hammer pin has no such detent that a spring can engage to keep it in place. Get a pair of Knights anti walk pins. Many use these, but others say the're a solution to a non-existent problem. Trouble is that this problem does pop up occaisionally. I personally use them as insurance, as does Grant and Denny from Denny's Guns.

[og556]

Would I have to remove every thing to install those pins or are do you keep all the parts in the lower and install ?

[ErikL]

can you take a picture of the inside of the lower with the hammer forward?

[og556]

I will definitely do that tomorrow after work.

[ErikL]

That will work...when you say walking out do you mean like the thickness of a credit card or less?

[Iraqgunz]

I have 500 BM carbines in my armory. Every single one of the pins has a slight "walk" as in they are not perfectly flush with the receiver. The issue would be if the pin were to completely come out while you are shooting. If it doesn't you should be good. Your hammer pin is held in place by a "J" spring that is contained within hammer itself. If you were to remove the hammer, and look at the hole where the hammer pin goes through you should see a piece of metal. That circular spring drops into the middle groove of the hammer and holds it in place.

The legs from the hammer spring hold the trigger pin in place. When assembled correctly the legs will be over the pin on the left and right side.

[Iraqgunz]

Todd,

The hammer has an internal spring called a "J" spring. This spring sits in the center groove of the hammer pin and that is what holds it in place.


This happens occaisionally. Those who have "Trigger Pins" walking many times don't have the trigger group assembled properly with the left leg of the hammer spring on top of the trigger pin in the groove that keeps the trigger pin from shifting.

But..as in your case, the Hammer pin has no such detent that a spring can engage to keep it in place. Get a pair of Knights anti walk pins. Many use these, but others say the're a solution to a non-existent problem. Trouble is that this problem does pop up occaisionally. I personally use them as insurance, as does Grant and Denny from Denny's Guns.