Testing, testing...

[JASmith]

...they did a thorough job. 5.6, 6.2, 6.5, 7.0 and 7.8mm projectiles were tested, each in two bullet styles (Barnes TSX and a "GP" bullet similar in design to M855A1 EPR) ranging in weights from 61 for the 5.6mm to 165 for the 7.8mm.

Tony,

I did a quick check and, if one keeps the same shape, 61 grain 5.6 bullet will scale to a 165 grain 7.8 bullet. (It works out to about 160 gr if one scales from .224 to .308 in.)

I conclude from this that they likely attempted to make the test protocol "fair and even" by maintaining the same shape of bullet throughout the test. We know that the 61 grain bullet is less effective than the 77 grain bullet in 5.6. We also know that the 165 grain 7.8 bullet gives up a lot in muzzle velocity when used in the 7.62X51 NATO.

Small surprise that the results favor the middle ground.

These tests may be definitive for those pursuing an already identified caliber and cartridge, but other tests have a good chance of having a different caliber coming out on top. This is especially true if one includes cartridge diameter and length as part of the test protocol, e. g., a cartridge based on the PPC for the 5.6 gives a significant velocity boost for the longer, heavier lead-free bullets even in the short action, the same is true for BR-based cartridges for 6 and 6.5 mm. Going to the 7.62X51 overall length and using smaller diameter cartridges would also give more latitude for the 6.5 & 7 mm diameters to show well.

It would be interesting to see what weight of bullet was actually used for the 6.5 -- scaling as inferred above would yield 95-100 grains. This could be a very interesting weight class for the Grendel.