I have my eye on a lovely rifle which unfortunately is a 338 Taylor. The cartridge is a 300 H&H case shortened about 1/4 inch with quite a sharp shoulder. I am trying to determine if the rifle might be a candidate for conversion to 340 Weatherby. Does anyone have any specs on this cartridge?

340 is longer and has minimal taper, you should be fine to rechamber

Make sure the magazine box is long enough and the action is the same.
Good luck
Dave

get a casting, and see