I built a cav arms on a bet/dare. I turned and chambered a light weight barrel and threw a bunch of spare mismatched parts together and actually finished assembling it at a LEO class. It was shot and passed around. 2-3K in 2 days of mixed ammo and mags through it.
not one failure. not ONE. that cannot be said about the brand new bushmasters (gas key came loose and a second had a buffer/tube friction problem), and the sigs that would NOT feed right.
I fully expected problems, surely SOMETHING would go. But that polymer is tough. 300 yards 6" plate hits with non magnified eotec was easy (as it should be)
Now we have probably 8k through it with a couple fail to feed but that is it. Its fired 300 black out, 450 bushmaster, and 5.56.
The take down pins are a little looser than when new but still good to go.
Cav-Arms should have gone with a better endplate. The cheap plastic one is just sad; had they gone with a solid instead of attempting a trap door, the result would be less embarassing. I replaced the ones on my CavArms lowers with the real deal or one from an RRA entry stock.
Other than the above complaint, I have had no issues with them. I am reluctant to put an RRA upper on one, since RRA is tight on an aluminum lower.