Nosler's #6 show's IMR4831 to be the "Most Accurate Powder Tested" and list 53.5gn (2910fps)as max and 49.5gn (2670fps) as bottom load. W760; 53.0gn (3018fps) - 49.0gn (2835fps), RL19; 55.0gn (3003fps) - 51.0gn (2779fps). Take into consideration that this is for the Nosler bullets, they used a 24" Shilen barrel and Winchester cases and Fed 210 primers. Their OAL is 3.340". Work up in to these max loads. Also, check out Reloader's Nest - a reloaders resource
, they have a lot of info on most every cartridge availiable.
As for the COAL; before the gauges were inventred, I would take the bolt out of my rifle and place the bullet to be loaded in to the chamber. Lay it in there with your rifle somewhat horizontal and gently take a 1/4' dowel rod (about 15" long and gently snug the bullet into the lands and grooves. Have another 1/4" dowel rod (DR) long enough (30") to push down the barrel from the muzzle end. Gently hold the short DR against the base of the bullet and let the long DR snug up against the bullet tip. I used a knife to "mark" this length where the DR enters the barrel.
Take the bullet out of the chamber, return the bolt and slide the long DR back down the barrel until it contacts the bolt face. Mark this length with your knife. Measure between the two marks. You now have your OAL for this bullet. Hope this helps. JohnnyK.