Grendel LMG

[RangerRick]

Perhaps "effective range" was not the best term to use. What I'm thinking is that the trajectory should be at least as flat as for 7.62x54R.

The challenge will be to design a FMJ bullet with BC good enough to achieve that trajectory, when launched at a MV for which the cartridge is capable.

Good question. I don't know if there is a generally accepted definition.

Maybe it'd be best to just show gel tests comparing wound channels of 6.5 Grendel and 7.62x54R?

The old gel test of the Norma 120gr FMJ does look very similar to Fackler's wound profile of 7.62x54R. It's conceiveable that a FMJ bullet optimized for 6.5 Grendel could do significantly better than 7.62 at closer ranges. At long distances (over 400 meters), Gary Roberts says there's no real difference between different calibers.

The data I've found suggests that the service round projo is 148 grains at 2723 fps. The cartridge seems to be capable of more than that, but maybe that's only in modern bolt actions and not military weapons. The Sellier & Bellot 150 grain FMJ goes 2840 fps out of a 28 inch barrel. That's very similar to the 7.62x51 and we know the Grendel comes close to matching those ballistics.

The Hornady .312, 150 grain FMJ only has a BC of .361, their 150 grain boat tail FMJ has a BC of .398, so we have them beat there for lead cores. Steel cores of the same weight would almost certainly have higher BC's because of the length.

That looks to be the biggest advantage of the x54: lots of room in the case for long bullets because of fairly low powder loads relative to case size.

With the higher sectional density we may be able to make up what the bullet lacks in weight to get similar penetration capability, particularly at longer ranges.

I have a buddy with a Mosin Nagant I could probably borrow to do tests, but my range only goes to 300 yards.

At what range do we need to demonstrate plate penetration?