[Hobbes96]

I'm intrigued by the idea as well. But, I'd have some concerns with the rebated rim. I know some calibers, such as the .22 Nosler, struggle with extraction in the AR platform due to having a rebated rim. Obviously Winchester must have got it figured out for the 400L. But, the 400L is essentially a straight walled cartridge, so I'm guessing because it doesn't have a shoulder, extraction is easier. But, by necking it down and introducing a shoulder, a 6mm wildcat might pose some problems for extraction with the rebated rim.

 

[Hobbes96]

I'm guessing that is why they have the threshold lower. Not sure why that they would go rebated rim vs the x39 case head. The only thing that I can think of is that the x39 case head is really not ideal for the AR platform. But, at 45k psi, I would think that it might be alright. Since the Grendel's max psi is around 52k psi.

 

[Hobbes96]

Nope, but I haven't really been looking either.