Military round comparisons

[Tony Williams]

Murray's 7mm UIAC is more or less a Grendel extended. The Carcano is close too. He designed a bolt a little larger than my 800 series AR15 bolt but smaller than an AR10 bolt. I machined them for him last year. The problem I see with the 7mm bullets is the BC is low until the heavier weights are used then because of the weight they are slow with the case capacity what it is.

Agreed, plus the other problem is that the weight of high-BC 7mm bullets means that the weight saving over 7.62mm M80 may be too small to be worth bothering with.

The Grendel provides the superior long-range performance needed to replace the 7.62mm combined with a very worthwhile weight saving, but only from a long barrel and firing high-BC lead-cored bullets. Combine the use of short carbine barrels with the current insistence on lead-free bullets (which will protrude more deeply into the case, reducing powder capacity - especially with tracer bullets), plus the potential for a polymer/metal hybrid version of the case (the coming thing) which reduces the case capacity by maybe 10%, and you get a performance shortfall which can only be made up by a bigger case. Something like the 7x46 UIAC necked-down to 6.5mm should do nicely.

And by the way, the performance from 20" barrels does matter, because that's likely to be the length of the tube of a GPMG firing any new intermediate round. At long range, a GPMG is surely more important than a carbine in terms of effective squad firepower.