Which powder should give best accuracy in an M10 Ross Sporter, barrel about 26 inches

[diopter]

Varget, H4895 or RL 17 (very close to IMR 4350)?
If it has an Enlarge Chamber, it is minimal based on fired FC cases.
Have new Privi brass and .312" 174gr Hornady RN and above listed rifle powders.
Just don't have time to experiment with them all.

 

[Eagleye]

You are asking a question that cannot be answered, since each rifle may have different characteristics.
I have a rebarrelled 1910 Ross 303 here, and it likes all of your listed powders plus: IMR 4064, IMR 4320,
Norma 202, Vihtavuori N 140 & 540, Ramshot Big Game, W760. If I had to choose 1 powder it would be
Vihtavuori N540 with 174/180 grain bullets. Great speed, and very accurate with the 174 Hornady.
If I were held to making a choice from your 3 powders, I would start with H 4895. Dave.

 

[Ganderite]

Any of those 3 would make good ammo, although I would not use RL17 for 150 gr bullets. It would be good for 175 and up.

I would use which ever powder is the cheapest.

 

[303EppsFan]

I found 4895 to work well with Horn 174 gr RN in my .303 Epps. Not best velocity in that cartridge but very good accuracy with that bullet.
My typical load usually involves R15 in the .303 Brit over Horn 150 gr Sp which doesn't help here, but I found it to work well in a variety of guns. It's a load I try now to evaluate or get a benchmark for a gun.