The 250 gr. R-P factory load clocks 2435 fps out of my rifle as a reference point.
I can get 200 gr bullets moving out almost 2700 fps with 59.0 gr. H4895 and match the velocity of the 250 gr. factory ammo with 60gr. of RL-17.
Tubal 3000 is in the GRT database, but the 6mm ARC isn't.
In the 6PPC using your barrel length and dimensions 27.9 gr. develops 3173 fps at 55kpsi with a loading density of 106%.
I use the same process that Ridge_Runner uses for forming 9.3x62 cases from 30-06 brass using a different (faster burning) flake powder that I have an abundance of and old oddball primers that I have no other use for. I've found that annealing the neck and shoulder area before forming helps...
I have a 6mm AR which is a 6.5 Grendel necked down to 6mm. It is built on a CZ5527 action and wears a 24" 1/10 twist Shilen barrel. The ARC has the shoulder pushed back .050", but the case capacity is close.
I'll send you a spreadsheet of all my loading data if you PM me your email address.
Actually a Brown Whelen is really close to a 9.3x62 case necked to 35 caliber. Just a different shoulder angle and being .010" larger at the shoulder.
I haven't has any issue making 9.3x62 cases from the 30-06 brass I had on hand. Prime a 30-06 case, put 5-7 gr. of Bullseye inside, followed by...
I would recommend this loading article.
https://www.slideshare.net/slideshow/working-with-the-22-hornet-ml-mc-pherson-winter-2012/42112731
My Ruger M77/22H shoots way better with MP-300 as compared to Lil'Gun with 40 gr. bullets. The MP-300 was slightly slower, but had a much lower SD as...