I’d go 5.56mm all the way. It’s tried and true, more ubiquitous, cheaper, can penetrate most armor, and for cheap practice a 22 conversion kit can drop in, which is currently priceless when 223 is $1.00+/rd. (It doesn’t have the knock down of blackout but skip to the end for that.)
As for Grendel, a major problem I ran into was the lack of market for parts. Builders benefit greatly from competition between co’s like Wilson, Faxon and Ballistic Adv. They drive the precision standards higher, and costs down, every year. The result: now the .223 industry standard is 1/2 MOA or better. I only found a handful of folks selling Grendel barrels at all in 2016, and they were not that reputable. Re: ammo, cheap Grendel was $1.00+/rd before the Bidenpocalypse, now it’s mythical. I sold my Grendel for an 18” Wylde coyote gun doing single hole groups inside 50 yards and <1moa regularly if i do my part, and a 5.56mm SBR for my HD tool. No regrets here.
BONUS: If you don’t have a suppressor to build a Blackout that’s “movie-quiet”, it’s really just a neutered 7.62x39mm. An AK can be had for much less than an AR in that dept, only you get to use words like “Nyet”, “gulag” and “vodka”.
Добрый день товарищ
Pronounced: Dobre’den tovarsich
Means: Good day comrade
Don’t got no AK, don’t want no AK, no I am not a gun snob…
Don’t know Russian, googled it. But learned this phrase in mock POW camp during escape and evasion training. Also about the same when I went to Hungary, Czechoslovakia, and Former Yugoslavia with the 1st Armored Division. They all said Dober-don (good day).
P.S. Russian Army ate at the same table in the d-fac with us at Tulsa AB, Bosnia. We handled, inspected and admired each other’s rifles. Same with German, Swedish, Finland, Poland, and whoever the hell else they sent down there with us. We didn’t understand a damn word we said to each other, but respect for hardware was mutually understood.
I’m somewhat surprised that everyone has left out PCC’s for someone wanting an AR pistol platform. 9mm is also a caliber that is extremely common. Not to mention, if you’re prepping for SHTF type situations, the magazines will be abundantly available. Even more so if you already own a Glock. This would drastically cut down the load you would need to transport, or give you a lot more room to stack 9mm mags instead of 5.56 style mags.
I have a 10.5 9MM GEN4 upper with the PSA conversion for a AR15 lower. it is a blast to shoot, accurate and like you said takes the same mags as my Dagger. and if I have to I can remove the adapter and put on 5.56 barrel.
will be getting a dedicated PX-9 lower when the Biden meme lowers stop…
I have an AK-V, and AR-V and am getting ready to pull the trigger on an Aero Precision EPC-9. I love the PCCs, so easy to stash, fun to shoot and 9mm is easy to lay hands on.
nice i have one of the first run EPC’s, i like it
i’ve got both a px9 pistol setup, and a px9 carbine setup. the carbine was gifted by PSA to me when i was fighting the beginning of my battle of cancer. I was pretty bad off, but they came through in a major way for me. and this rifle is just one of the ways. a 16" red carbon fiber barrel w/stainless steel is pretty bad ass. its the Official Gamecock Operator Rifle. 
lemme dig up a pic of it. I did add some parts to it… anything that is anodized red is from Strike and did finish it off just right… still contemplating on changing out the grip though…
This photo below, is me with both Jamin and Josiah, when i was presented the rifle. a day i’ll never forget.
thats awesome, would look killer with a red ETS mag…they make a 40 round
i’ve not seen those… red glock mags… who’d of thought. i need to pick one of those up for sure.
thanks for the link. 14 bucks isnt bad really. those would look good in the rig thats for sure.
I took that bottom pic, and i think was when we met @sean.psa for the first time.
I dont know who took it but you’re right it was the first time we met @sean.psa
That sounds right to me. Love that gun.
me too. when we all get to a range sometime together ill bring it and we all can shoot it.
That rifle looks Bad Ass. Is that a Dip coating, or a Wrap?
The GamecockOperator Rifle is a Hydro Dip on the parts from what Jamin and the guys told me. I absolutely love it and cherish it.
Good to know, thanks