I went the pawn shop route to get the base gun for my house shotgun. I found the crappiest but still functional 12 gauge Remington 1100 within 50 miles of the house. It had camo duct tape on the wood that also covered up the split toe on the butt stock, a bulge in the barrel and the muzzle was out of round. It cost me $200 'out the door' (tax, NCIC background check, ... included) and I think the feller at the pawn shop thought he'd found a pilgrim to fleece. That was alright because all I really wanted was the receiver, bolt and mag tube, which -apart from a little rust on the sides of the receiver- were in great shape.
After a detailed disassembly and cleaning that included the use of a half a case of Gun Scrubber and about 3 hours of chipping the built up powder residue out of the receiver because it had apparently NEVER been taken apart, I called Remington and ordered a new barrel (21" smoothbore slug barrel with rifle sights and choke tubes) and a new set of O-rings (the old ones were really ratty). Then I got a hold of Speedfeed and got one of their Speedfeed III stocks and called Surefire Technologies for one of their Responder forearms. While I had the phone and credit card out and warmed up, I got a hold of Scattergun Technologies, who were kind enough to sell me a 6 shot side saddle carrier and one of their mag extensions.
For about $600 (and the single biggest cost was the Surefire Responder forearm- its' cost was more than the gun), I ended up with essentially the same thing as the Scattergun Technologies 1187 K-9 model but at half the costs.:biggrin: The ONLY differences are mine is an 1100 rather than an 11-87 that has has open sights rather than a ghost ring rear and everything except the parkerized mag extension is blued.
That was over 10 years ago and I finally ended up using it this weekend- on a raccoon that was probably rabid. Two loads of Remington 2 3/4" #1 buckshot (one of the 16 ball loads that are on the market) surely makes a mess at 30 feet.