First off, I don't have a ramped bolt...I have a 9mm hammer in my Bushy lower for my RRA 9mm upper. I know the answer in reverse...what I mean is that I know you can't use the .223 hammer in the 9mm, but can you use the 9mm hammer with the .223 upper? Have I confused anyone yet?

OK, I know this doesnt answer your question but...The 9mm hammer is slightly shorter and has a more rounded face than the standard hammer. RRA seems to have two .223/5.56 bolt types out there,1 with a slight short ramp and one with a more M16ish ramp profile..If youve got the short type it may work,,,but with the M16ish ramp you may have problems with the hammer not recocking,,Also the 9mm ramp setup seems to be slightly offset to one side so the "short .223/5.56 bolt style" may have clearence problems. As a side note the RRA 2 stage hammer is even taller than the standard hammer so i dont think it will work without ramping...Anyway I have RRA 2 stages installed in all my lowers and they are a PITA to drive the pins in and out so i cant test the theory...So if you have a 5.56 upper i say put it on the 9mm lower and hand cycle, If that goes well give it a try.....Sorry i cant really answer your questions...............UNDERDOG

That's still the best answer I've gotten...I figure I can just try it when I get home. The question just kinda popped in my head while sitting at my desk, so I thought I'd throw it out there....thank you.

Um its the only answer youve gotten...[lol]Like i said sorry i cant help more,Id try it myself for ya but those 2 stage pins are a pain.....UNDERDOG

Yup...that was an attempt at humor...I'm funny, huh?

I just have the standard 9mm hammer from Model 1 sales...RRA was out at the time I ordered. I'll give 'er a go tonight. I think it is the slightly ramped bolt that you described...maybe there's a chance.

I have a Bushmaster .223 lower, and numerious uppers includung 9MM(Dalphon). All the uppers work fine on this lower.