I was kinda challenged by a friend to build this one. Cost, light wight and practicality were the three criteria. Was intended to be a home/farm gun.
Here is a Cav Arms lower I bought out of curiosity when they were $50. I decided to go ahead and build it for a school I was going to because the instructors (friends of mine) insisted that homebuilds were not as reliable as factory, plastic lowers were even less so. (I was afraid they were right on this one but have no experience on the matter). So here we go
$50 Cave arms plastic lower
$25 used Colt FCG
$75 used Bravo company bolt and carrier
Some misc parts to round out the lower
$14 A Wolff heavy buffer spring
$69 a blemished BCM upper
$80 used Colt lightweight barrel, carbine gas system cut to 14.5" with and AK flash suppressor silver soldered on. (I had the extra AK suppressors around, they were running $15)
Viking tactics sling (extra)
$70 High intesity LED Lenser light (this aint your daddy's LED light, it works)
$10 I machined the free float tube
The EOTECHs are mine and I normally have it on the "go to gun" minus the magnifier.
So After 3 days of running, barricade shooting, in and out of car drills and shooting from cars, from 7 to 200 yards and approx 1750 rounds.....
One magazine related failure. Period. One.
The Sigs turned in NUMEROUS mag failures and a few FTF, The HK had a few "issues"
and the Bushmasters a large agency near here bought crapped out 5 out of 5.
Accuracy is subjective, I typically out group 90% in these classes and this was not very different (I'm not good, they just suck) 100 yards EOTECH minus magnifier was giving me 3" 10 shot groups while under time limits.
So its good enough for me.
Below it is an AR10 16" Carbine I machined recently too.