.300 AAC Blackout rifle

I have a .300 AAC Blackout rifle that i’m trying to swap for a remington 700 .308. The rifle started out as a .223 and then became a build of my own with help from my gunsmith at S&B shooting sports. This rifle has a 16 inch stainless steel barrel with carbine length gas system and the gas block has been set so it will shoot sub sonic and super sonic ammunition. It has a Magpul rifle stock on it and the weights and springs in the stock along with the gas system have been adjusted to allow it to cycle correctly. It has a Magpul handguard and pistol grip along with a new upper reciever shell and bolt carrier group. The lower reciever shell is from the original rifle but the trigger group is new. The detents on the stock are new. The magazine release is new as well. Rifle has a set of canted iron sights on it as well as a bipod and magpul angled fore grip.Runs very well but for some reason it does not like remington UMC ammo. I’ve had problems with this ammo in multiple firearms however.
I am looking for a remington 700 .308 preferably stock. The less that’s been done to it the better.