[Tspeis]

Since the 416 was originally designed as a machine gun with a select fire lower, I think it's safe to assume HK includes full auto hammers with the factory lowers. So, for those of you who have uppers, what kind of hammers are you guys running on your lowers? Below is a picture of two different hammers. The one on the left is identical to the one used in the factory 416 lower. The one to the right is a semi auto hammer, used in MOST commercial lowers. I'm wondering if the factory full auto hammer will engage the firing pin block safety sooner during the firing cycle than the semi auto one. Note the extra material on the top and front portions of the full auto hammer.

Anyone know what the legalities as far as putting an M16 hammer in a semi auto lower would be? Obviously, the gun would still fire semi auto only, but I know the ATF is very finicky when it comes to putting M16 parts in an AR15. Though, a lot of manufacturers seem to be including full auto carriers as of late without any problems. Any help or suggestions would be greatly appreciated. Thanks!


Tspeis

 

[Tspeis]

I found what looks like a full auto M16 hammer without the hook on the rear, thus making it a semi auto hammer. Looks like it should be fine as far as NFA rules go.

 

[Johnnyc]

The F/A carrier issue is one of those "yes it's ok, but no it's not, but go ahead and do it anyway." There's a scan on one of the forums of the letter that pretty much says exactly that. The trigger however, is a no-no. That's where the ATF really gets its panties in a twist is when you have F/A fire control components in a lower. Similar to restrictions on trigger packs in 9x series lowers. The trigger that Tspeis posted would be legal as it doesn't have the little tail. Quite a few people use M16 hammers with the tail filed off in their 9mm uppers.

 

[JoshNC]

It is very easy to modify an M16 hammer for semiautomatic-only function. Grind off the leg that engages the automatic sear and you're good to go.