Originally Posted by Sako7STW
Would you mind throwing a .340 Roy into your calculations there? Would be interested to see how it stacks up. I am really thinking on buying a .300 Roy in the Vanguard then retubeing it with a 28" stainless fluted in .340 Roy or .338 Tejas the next year when I have more funds again. My bro has a 300 WBY right now and has everything to load for it so the only thing I would be out is brass.
340 Wtby 225 gr bullets average max velocity - 2927 fps
338 win mag average 2787 fps
338 RUM average 3144 fps
The case length of the 340 at 2.825" is even longer than the 338 RUM and would further be restricted by mag length and is belted. Being belted is not a killer but the brass manufacturers typically put a lot of head clearance on belted cases between the new case shoulder and typical chamber shoulder.
IMO if I wanted to go for a 338 heavy hitter (and didn't have one) I would find a Winchester (3 position safety) rifle in 264 wm, 7 rm, 300 wm or 338 wm and rebarrel to a 338RUM and get a Wyatt's box. Or if I had an action that I could not get a Wyatt's box I would rebarrel to a 338/375Ruger (will fit easily in a 3.4" magazine)