6mm ARC

[grayfox]

I just did a quick look-back on some earlier QL threads on here, on the Grendel cartridge. One common theme was the theory that for a shorter case, like the Grrr, primer ignition can bump out the bullet, both starting it out velocity wise and enlarging the effective case volume for the powder burn. Both of these seem to impact MV performance but QL was variously characterized as over- and under-predictive. It was also commonly said that the MV curve's slope matched mfr and reality curves... only offset by a more or less delta-velocity figure -- Klem and JAS in particular worked this out in some 2019 posts. Finally, some were able to match up QL predictions to their real-world MV's by upping the case volume from ~35 or ~36 (depending on the commenter) to ~38 grs.
If these things are put together into a common theory then a bump of the bullet would increase the effective case volume, and the movement and geometry being changed from the QL model, MV might suffer/predictions-off, but be some relatively constant delta-value with similar slopes.

I write this to pose that perhaps the same things could be expected in our new, short-cased 6Arc, esp where lighter bullets of ~100 gr (vs the Grendel 123 gr) are concerned. Relatively slower powders burning for the 6Arc will also have some kind of impact.

It will be interesting to see how real MV's, and real pressure, come out in comparison to QL.