Noticed that subject calibers,not all I am sure, but Ruger and Douglas barrels are 8 groove. I have a No.1 458Lott and it is 8 groove and curious what the "science" might be with that many grooves?? Just curious for in process of building up No.3 in 45/70 and it will be a Douglas 8 groove/20twist/23"long.

I just know that the "Ballard Rifling" on some current 45/70 chamberings is deeper for shooting lead bullets.

The number of grooves means nothing; but in a barrel that big of a bore, each "land" on the button, or cutter if broached or single point cut rifled, has to remove less metal than if you used a smaller number of grooves. Look at a trapdoor with 3 grooves; the grooves are very wide and required a bigger rifling cutter. Marlin uses 12 grooves except for their "Ballard" rifling on their 1895s. Douglas and most modern barrel makers use 8. Not something to be concerned with, how many grooves you have.

OK, thanks for the feedback. Just picked out my barrel this day, Douglas No.5A and will be 18 twist and 22" long, 8 groove, cal. 45/70 Gov't. I'll shoot both GC/PB and jacketed bullets in the rifle and should work well for my purposes.