AR15 hammers

[jblackfish]

Can anyone explain to me why some hammers are notched and some are rounded? I have two complete lowers, one I built and one I bought and have one of each hammer. Why the difference and does one work for some uppers and not others, etc. I'd appreciate the explanation. See photos:

 

[HOOfan_1]

The notched hammer is meant for semi-auto bolt carriers. I think Colt introduced it as a safety feature to prevent slam fires

edit: here is an explanation

http://www.ar15.com/content/legal/AR15-M16Parts/

better discussion

http://www.ar15.com/forums/t_3_118/...15_hammer___why_the_notch__why_the_tail_.html

 

[jakk280rem]

I believe the notched hammer was introduced by Colt for use with their semi-auto (unshrouded) carriers to prevent an out of battery firing condition.

 

[68wj]

Stops "automatic" fire if the disconnector doesnt hold the hammer back. It snags the firing pin and stops the forward motion of the bolt carrier.

 

[Dr.Rob]

Also notched hammers are bad (less reliable) for 9mm uppers.. or so I have read.

 

[briansmithwins]

The notched hammers get hung up on the firing pin when you have a unshrouded bolt carrier. This damages the firing pin retaining pin as well as the firing pin.

They have no positive value.

BSW

 

[taliv]

They have no positive value.

?

if you have a shrouded carrier, it doesn't matter. if you have an unshrouded, use the notched.