How hard/easy is it to take a surplus gun parts kit and built a complete rifle? I've seen different parts kits around and have always wondered how reasonable it is to find the missing parts and build them out. Here's a sample kit that just came up on Midway:

http://www.midwayusa.com/product/909439/military-surplus-ak-47-polish-under-folding-stock-parts-kit-762x39mm?cm_mmc=pe_weekly-_-milsurp-_-ak47kits_20150722-_-Main_Image

Depends on the gun and the kit.

AKs are going to require a few specialized tools, and the really crappy part is any new import kits don't come with a barrel because the barrel is a "machine gun part" o.O

So you're going to need a barrel +$140, a receiver +$100 and any tools you don't have to assemble it.

So if you're just a DIY guy looking for a fun project go for it, but if you're looking to save money you're already into WASR territory.

I miss the good ole days of cheap and plentiful parts kits. When it comes to building them my experiences are as follows:

AR15 is probably the easiest as the rifle is pretty much built to plug & play.

FALs were also pretty easy just a torque wrench, receiver & barrel clamps, and some LS gauges and you could crank one out in about 1-2 hrs

AKs & Galil were difficult even when you had the original barrel. Specialized tools needed to do the riveting plus pulling out and pressing the barrel back into the trunnion while keeping it from canting. Now with new barrels you need to actually headspace which was just a check with older matching kits.

Hks unless your comfortable with a welder don't even think about it.

1919s very doable if you have access to a press and a lot of time & patience. Built mine with a guy who knew what he was doing and it still took us all day.

Finally when it comes to one off kits and sub machine gun kits most of the time they are cheap yes but require a lot of know how to get them running and you need access to mills & lathes and time or a lot of $$$