I mean, I think most of the shorter, lightish cans on the market are this footprint? 6” can, 8 or 9 oz, most of them are available with a 308 bore I think? This category seems crowded rather than sparse to me, its clearly a popular category. (My dd STI, nomad ti, etc, etc). That use but under 8oz , 3” muzzle forward otb would be slick if it could be done. Its probably limited by being a hunters can rather than a shooters can, but Id look hard at it.
I dont own a 6mm. I get theyre popular, but outside rokslide I think “most” folks are using 7mm and .308 bore cartridges for hunting.