GRT = Gordon Reloading Tool, similar to Quick Load but free following the passing of the author.
69 gr. of RL-19 and 65 gr. of RL-17 simulate as maximum loads.
308 Norma Mag is listed in GRT data base. 75 gr. of Retumbo or N570 is ~105% loading density with 3400 ft-lbs of ME at 51kpsi with the 200 NAB.
70 gr. of RL-22 is 100% loading density at 63kpsi and ~3700 ft-lbs. of ME.
71 gr. of 7828 is 100% loading density at 63kpsi and ~3800 ft-lbs. of ME...
I have far rarer M88 rifles, but my 358 was the longest search for one at a price I was willing to pay.
I still have some 200 gr. Accubonds and I use 47 gr. of IMR 3031that delivers 2568 fps.
This is maximum load by most manuals and over max in others. It's perfectly safe in my rifle.
The 225...
I have dozens of lever guns, but my pre-64 M88 in 358 Win. would be my all around favorite. Cast bullets... Check, 38 caliber Pistol Bullets.... Check, 225 gr. Nosler Accubond.... Double Check.
John
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.