Oddball AR's

My current AR wildcats are two rechambered 300 blk barrels with carbine gas lengh gas systems.  one in 30 Herrett Rimless and the other is 30BRX.  Both are fun but require non standard magazines and bolts. 
30 Herrett Rimless uses trimmed down 6.8 SPC brass as its parent case while the 30BRX uses cutdown and trimmed 308
Winchester cases (I've since switched to using reformed 22-250 cases for less case trimming and reaming of the neck).
The 30 Herrett Rimless equals 7.62x39 in ballistics but doesn't have such a sharp taper to the cartridge case which means I don't have hto deal with heavily curved mags like some AR-39 users have to deal with.
The 30BRX wildcat ballistics can match a 308 Winchester in a standard bolt-action rifle but because my AR15 bolt is designed for the 450 Bushmaster it has a pressure limit of 42k PSI which means I load my 30BRX bullets using 30-30 Winchester power levels.
I built both rifles as experiments in developing an effective 200 yard deer rifle in 30 caliber using 150-200gr cast bullets which the former 300BLK barrel's 1-8" twists would not be a hinderance and at times a boon.
I did have a 300 Apache (simply a necked up .223 Rem case) chambered AR a few years back that was very nice but due to the case length and the magazine size limits, I only could use light bullets (110-125gr) or heavier bullets (anything over 130gr) seated deep and past the case neck which ate into case volume for powder as well.  I never got it too match 30-30 Win velocities but it did equal 7.62x39 performance in the 125gr weights.  Would I do a 300 Apache AR again?  sure, but I'd also want to match it up with a custom barrel (1-12") twist to match up with the light weight 30 caliber bullets to see how accurate I could make it.  1-8" twist is too tight for the lightweight cast 30 caliber bullets in my opinion.  
For non wildcats, I also own a 6.5 Grendel AR15 upper and Its a tackdriver with both jacketed and cast bullets.  I use it in NRA Highpower matches and I'm almost set to commit to another buying a near-twin of the Grendel but in 6mm (6PPC) for my next set of AR experiments (I'd of course have to purchase some 6mm bullet molds as well...)

The earlier post of a 7.62x25 Pistol Caliber Carbine AR definitely would perk my interest in another wildcat if I didn't already own a 9mm AR carbine.

Bruce