I have a single preban lower, and I want to use it with three different, preban uppers.

The 9mm is a KKF, Colt style using Uzi Mags.  I know I will need to add and remove the magblock when converting to and from the 9mm.

Do I need a 9mm hammer or can I use the standard .223 hammer for the Colt Stlye upper?

When I remove the 9mm upper, do I also need to remove the 9mm hammer to when I go to the dedicated .22LR upper?

TIA

TRG

Find a hammer that looks like this, and use it for all 3 caliber-- basically an M16 w/the lug removed. The std AR hammer with the "notch" will lock up right now as soon as you release the charge handle with 9mm, uless your bolt is "ramped".

[img]www.imagestation.com/picture/sraid58/p7a21929478de21856da2653f457a76fc/fc681fb2.jpg[/img]

Thank you for the picture.

I printed a copy for reference.

TRG

where can i purchase a hammer like that?  

DPMS sells the hammer you are looking for.

I talked to KKF via email and he explained how to modify a standard AR hammer to allow it to function with all three calibers.

I used a simple bench grinder to make it work.

It will fire a round with all three uppers. .22, 9mm, .223

TRG

UPDATE and WARNING

I removed too much material from the first hammer.  I ground the two 'peaks' on the top of the hammer until there was no material visible between them.  I did this because I felt that leaving material between the two peaks might for a rough surface edge and cause unnecessary wear.

I was wrong.

I continued to have the hammer fail to lock in to battery.  I might fire a single shot, sometimes two or three, and then the hammer would be down on a live round.  

This morning I located a spare hammer and reground it.  I removed only a 1/16th of an inch of material from each peak and it works GREAT!

I can switch from 9mm to .223 to .22LR (Ciener kit) with no problems in functioning.

So....If you want to do this yourself, just remove a little bit of material.  Not too much.  Function test it and then remove more if necessary.

Surprisingly enough, even the bad hammer would function in all three calibers, I assume that too much material was removed so that the inertia of the hammer was not enough to catch in battery, and there was not enough on top to get pushed down by the bolt.

YMMV

TRG

Buy an M16 hammer and cut the tang off the end of the tail (making it AR-15 legal). This way you don't have to experiment or grind on an area close to the face where the heat of grinding could affect the temper of the metal causing early wear.

Besides the hammer, wouldn't you need a liter recoil spring?

My recoil spring is well used.  I have fired about 1000 .223 with it.  

I tried a lighter buffer, but I had failure problems.  I put the heavier metal buffer back into the lower and things are a-ok.

TRG

Use your F'n .223 hammer and ramp your carrier. Ramping saves the hammer pins and the receiver bearing material for the hammer pins from elongation.  Butchering your hammers wont prevent hammer bounce as well.

You are correct, but this was not a solution for hammer bounce.  

I wanted to check the 9mm upper function, first.  The carrier did not come ramped.  If I had sent the carrier away for ramping, then test fired the weapon, any lack of function would be hard to explain to the manufacturer.

Modifying the hammer works just fine as a solution.

Ramping the carrier is the long term solution to prevent excessive hammer impacts.

I learned about ramping on AR15.com.  I have done extensive testing on ramped and non ramped 9mm carriers.  Using a layout dye, Blue Dykem, one can see the rubbing pattern of the hammer on the bolt.  The non ramped bolt reveled intermittent, bouncing, wear marks on the bolt. However, the ramped bolt had one uniform wear mark.  


Ramped bolt pic:
[img]http://users.zoominternet.net/~subguns/public/carrier-1.jpg[/img]

Isn't it illegal to put an M-16 hammer in an AR, even if it has been modified? Aren't BATFE that much of a bunch of Nazis about it? Also where can you send a 9mm bolt and carrier off to get ramped? I gots the same dilemma. 1 preban lower and want to build a 9mm upper over the summer.

No.  ATF "advises" against doing so, but it's not actually illegal, unless the weapon fires automatically in that configuration.

Besides that... once you cut the catch off the end, it's no longer an M16 hammer.

Hrmm,



I was thinkin of the M16 hammer then I ramped the carrier (works great) and wouldn't the possession of the "unground" M16 hammer and an AR15 = unregistered MG? in the ATF's eyes?  for at least the ten minutes it took to open the shipping package and grind the catch off?

I know that sounds retarded, but I have heard of ATF intercepting mail and then prosecuting, etc...

Kinda like my buddy and his friends in Canada fishing.  It was the last day of the trip and they had thier limits of fish all frozen and ready for the trip home, and the MNR (ministry of natural resources) came into the cabin and checked thier licenses and such. Then they began counting the filets in the freezer.........and then the ones in the frying pan they were cooking for that nights DINNER!  5 fish too many!!! Whamo! $100/fish fine!  

Yeah that sucks.  I know you would prolly never have an issue with the M16 hammer like that,  but man I'd hate to find out the hard way, with that agent trying to make a name for himself/herself......