well, there are those who like the quackenbush(spelling?) big bore airguns(he makes all of the guns he sells...and from what i've heard, they're extremely effective), and others go to websites and order a career dragon slayer .50 cal airgun, or a big bore 909(one from samyang, one from shinsung...both korean) and use them, or maybe even get them tuned a bit, but they work quite well also...personally, i wouldn't want to wait for my rifle to be made, cuz i'm impatient, haha, so i would go with a korean rifle...probably the .50 cal, and then get it tuned to get a little more power. if you go to pyramydair.com, click on tips and tricks on the left, on that page should be a review of the dragon slayer and a little bideo on the bottom of the page. as for noise, i've heard that they are as loud as a centerfire, and kick pretty hard like a shotgun, but i personally have never shot one. there are also two 9mm rifles on pyramydair's website...check em out...as for the quacjenbush rifles, just do a google search, and i'm sure you'll find his website...i know there is another gentleman that makes bigbores, but i can't remember his name...maybe someone else could chime in on this...
hope i helped
Dave