I just looked at Hodgdon load data. Varget is about as slow as practical./ full case. H380 is also about as slow as practical./ full case. Staball is much slower. If you're set on trying it anyway it would be a compressed load and less velocity. Ramshot( big game) powder might be an option. If it were i , i would abandon heavy bullet's and opt for the barnes ttsx 180 grain. Much better all around. Barnes load data is on line free.Do any of you 35 Whelen guys have an opinion about or some experience using Staball 6.5 powder with a 260 gr bullet?
Will the burn rate be too slow?
Actually it's right up there on the weights the OP wants to use.Varget is about as slow as practical./ full case.
Back then they didn't know about the great advantage of copper bullet's. A 180ttsx at much higher velocity will out penetrate the heavier slow lead core bullet. The 180ttsx goes in 180 grains and comes out 180 grains leaving no lead contamination in the animal. High velocity copper bullet's = deeper penetration even through big bones. New technology is wonderful.Bigger bullets is what the Whelen was designed for. Poor man's magnum back in the day.
Back then they didn't know about the great advantage of copper bullet's. A 180ttsx at much higher velocity will out penetrate the heavier slow lead core bullet. The 180ttsx goes in 180 grains and comes out 180 grains leaving no lead contamination in the animal. High velocity copper bullet's = deeper penetration even through big bones. New technology is wonderful.