Hello.

I've read the FAQ more than once or twice, but I'm still not 100% sure I've understood which hammer type works with what.
I have a newish Bushmaster carbine and will be getting a Colt-style 9mm upper soon.
Is there a way to avoid swapping the hammer, in other words, will both uppers work with either the BM 223 hammer or the 9mm hammer?
If not, how will the weapon and I be if I forget to change the hammer and try to use the wrong upper with the wrong hammer?

Thanks for your kind advice.

Yes, get your bolt ramped by Joe Black.

This is the part that I don't understand. I talked to someone about ramping my bolt and he said that I'd still need a different hammer if mine had the little notch at the top front.....so WTF?

I want to know too......free BTT.

The Colt design has a few quirks,,,,,,, but the best way to run is have the bolt ramped to copy the ramp seen on M16 carrier, and use a M16 style hammer with the secondary sear lug removed for legal semi-auto use.

M16 in 9mm is M16.....

The std AR hammer found in most (has that notch at top of face) usually does not come back far enough for it work the engagements properly.

This is what you want, then swap uppers all day long and keep on running.---

I have a 223 hammer in my RRA 9mm and it works fine...can switch between uppers all day long!

I'll try and make this simple since I wrote that abomination about hammers in the FAQ.  it is only from what I understood from others.

Your bushmaster is most likely equipped with a "notched" AR-15 hammer.  That is to say there is a small nothch cut out of the top front of the hammer.  If you mount a Colt style 9mm upper (such as a Colt or Rorck River 9mm upper)  and do not change the hammer what is going to happen is you will most likely get one shot off and the hammer will bind up against the bolt and you will need a hammer and punch to get the receivers ap[art to fix this mess.

There are two solutions to perevent this.

1.  Hammer replacement

A.  Replace the hammer with a "DPMS" style AR-15 hammer.  It looks exactly the same as the hammer in your Bushmaster EXCEPT that there is no little notch in the upper front face.  Your gun should run fine with both 9mm and .223 uppers.  The hammer in the pic above is similar in appearance to the DPMS AR-15 hammer.  

B.  Replace the hammer with a Colt or Rock River 9mm hammer.  Will work fine with 9mm upper, I have heard rumors the hammer may not reset properly with a .223 upper

C.  Get an M16 hammer and cut off the "tail" that sticks up, such as in the picture above.  Should work fine with both 9mm and .223 upper.  As for the legality of getting an M16 hammer in Finland I can't say.

2.  Bolt ramping.  When the botl is ramped the weapon should work OK with all hammers EXCEPT the 9mm hammer- the 9mm hammer won't reset sometimes.  

OK, hope that helps.  If anyone see a mistake in the above please let me know.

Dawg

I have a DPMS type "rounded" style 223 hammer in my RRA 9mm setup.  I have never had a problem with it AT ALL, it works 100%.  This way you can switch between a 9mm and a 223 upper.  Best of both worlds!

Quoted: Your bushmaster is most likely equipped with a "notched" AR-15 hammer.

Yep.  I have a Colt-style 9mm hammer on the way with the upper so I probably will play the changing game for now. Have to remember to order an M16 or DPMS style hammer next time I order some parts from somewhere.

BTW does anyone have better pics of the ramp conversion? I would be hesitant to attempt any DIY based on the ones in the FAQ. Anyway, getting another hammer is probably much easier.

Thanks...