www.aimsurplus.com is another good one. There are quite a few listed in the C&R forum of AR15.com. I've sent my C&R to several places, including Brownells, to get discounts on parts, supplies, etc as well.
www.gunbroker.com has the occasional deal as well. I got a Mossberg 44 US .22 LR rifle for about 250 less than what my local shops were trying to sell em for.
The Armchair Gunshow.com
Cherry's Fine Guns
Cole Distributing Inc
Collectible Firearms and Edged Weapons
David Condon Inc.
Florida Gun Works
Inter Ordnance of America LP
Martin B Retting, Inc.
Military Gun Supply
NEW PHILLY SPORTSMAN
Ohio Ordnance Works
Military Gun Supply.Com
Old Sacramento Armory
Ricky's Gun Room Inc.
Samco Global Arms
Southern Ohio Gun
Treasure Hunt Arms
I have personally checked out the following
Armchair Gun show /old town station
Uncle Sam stands behind CMP They buy from him
Milsurp.com can be trusted
Shotgun new- They check out their advertisers
What I generally do is inquire about them in their home area.BBB Chamber of Commerce, and from time to time the ATF.Ask on different forums is good, but ifthey aren't known in an established business,thenyou may be taking a chance.remember some of the stuff we buy cost big bucks.The only thing I have against some of them is I don't like to bid or dicker.I quote them a price and I stand by that decision..I buy and I trade, once in a great while I'll use one as part of a bid to buy.But you have to be your own judge.Just be careful
Not everone is honest I learned that the hard way
I've purchased several C&R rifles off of gunbroker with nice results.
Perhaps, if I am very lucky, the feeble efforts of my lifetime will someday be noticed, and maybe, in some small way, they will be acknowledged as the greatest works of genius ever created by Man.
- Jack Handey