I've got my own shorty 270 AR on the drawing boards. It is a 1.75" long extra tapered 300 RCM case. Tentatively it will be close to the 270 Win. shoulder angle, and will run through one of the new Black Hole magnum left hand uppers. Andy Baker figures 100 grs. is the minimum weight to get any accuracy out of their AR platform, in 270. So a 1 in 14-16 twist will be about as slow as I can go. This will actually be close to the ancient 6.5 Jap, in capacity. I designed it as a 270 to get around the solid gilding metal to lead jacketed bullet boundary. If I used lead cored bullets, I would go with the 6.5mm bore.

At AR operating pressures, I'm going for well over a ton of striking energy. This wildcat will answer how much more you get from the larger diameter RCM cases, compared to the smaller 6.8mm Spc. II's. I'm looking at considerably more power than the 277 Titus, in a Md..99 Savage lever action. The downside is that this rifle will not pass muster with the Republic of South Africa, so I may have to make up one on a Mauser M-98 Military job. The closest I've come so far is using Barnes 110 gr. TTXPs in a 270 Win. on small African plains game. Except for jamming up after nine inches of penetration in the spine of a Springbok, they worked really good. My P.H. wouldn't let me go after anything larger than a Blesbok with them, though.

7 mm Rem Mag necked down to 6.5 is the 264 Win Mag.Have a few 7MM Rem Mag cases that got mixed with my 264 cases and they sized and shot just fine.Usually I don't use them to save the confusion of the wrong headstamp though.