so even tho the ar15 is brand new, i can get a DIAS legally with just a form 4? didnt know that. Would it be select fire? and how is the reliability?
vaeevictiss, I did the ATF Form 4 and bought a RDIAS back in 1986..... the dealer popped open my Colt SP-1, swapped out a couple of civilian parts with military versions, and then inserted the RDIAS down into the recess at the bottom of the lower receiver.
I've never had any problem with it - I've fired a few hundred rounds of .223 and a few thousand rounds of .22 LR with a Ceiner conversion kit. I never noticed that it affected semi-auto fire, and it didn't require any special fitting/tuning, but maybe I was just lucky (?)
As far as reliability goes, I have no complaints with .223, but the .22 LR conversion jams occasionally.
As Skans pointed out, the RDIAS is the "machinegun" listed on the ATF Form 4, so you're free to install it on a different AR platform/caliber any time you choose.
Also, as Skans mentioned, the price is up in the neighborhood of $10k nowadays (if you can find one for sale).