Hello - I'm thinking of buying a 9mm upper to put on my RRA AR15 lower with a RRA 2-stage trigger. I've been doing some reading, so I understand the concept behind ramping the 9mm bolt. My RRA hammer has a flat face so I am told you technically don't have to ramp the bolt. Here is what it looks like, sorry I do not know how to attach a photo:

http://www.bing.com/images/search?q=rra+two+stage+trigger&id=5B1B694ABDC94491C7E369B5CD44013DE3286B29&FORM=IQFRBA#view=detail&id=5B1B694ABDC94491C7E369B5CD44013DE3286B29&selectedIndex=0

In any case, I still have a few questions:
1) Is it a good idea to ramp the bolt regardless of the type/make of AR hammer in the lower. For example, if I would get another AR lower with a DPMS parts kit and hammer, would I still be advised to ramp the 9mm bolt? (I realize that you don't have to ramp the bolt if you're using a 9mm hammer, but I want to stay with my AR FCG.)

2) Some of the reading I've done says that the 9mm bolt is hard on the lower. In which case I would definitely get another lower, or even a dedicated 9mm AR. Will I damage my RRA lower if I switch back and forth between my 9mm and .223 uppers?

3) Other than a 9mm complete upper and a magwell adapter, are there any other parts I would need to change out in my RRA lower to work with the 9 mm upper. (One part I have heard you should change is the buffer, although I am not sure why.)

Thanks

If I understand it correctly, the notched hammer and unramped bolt was another of Colt's attempts to prevent any sort of full auto conversion of their guns.
It is also my understanding that the ramped bolt is much easier on the hammer pin; due to the abrupt nature of blowback recoil in the pistol calibers, much greater bolt velocity (and impact on the hammer pin) are present with the pistol caliber firearms.
Moon