Alot depends on your recoil tolerance ( or how much noise/muzzlebrake you can tolerate). If you handload, shucks, a stout 270 with Hammers/Barnes is wicked..."almost' like a 7 Mag. So, as they say, get closer. If you handload, again, you can teak a 338WM with Barnes 160 or 185, Hammer 213 HH, wicked flat.
OR You "could" keep your current .270 setup, just get a Leupold CDS 2.5x8 or 3.5x10 and dial it in. Stay away from shoulder bones, wait for a broadside or slight angle into lungs. Wind will be an unknown, of course, 400yd shots require tons of practice. Its a commitment only you can make. My average range for 4 cow elk is 170yds. I used a 30-06 (135 steps) .375 H&H (200yds) .338 (250yds) and a 300WM (100yds) ha. Have a ball friend!
OR You "could" keep your current .270 setup, just get a Leupold CDS 2.5x8 or 3.5x10 and dial it in. Stay away from shoulder bones, wait for a broadside or slight angle into lungs. Wind will be an unknown, of course, 400yd shots require tons of practice. Its a commitment only you can make. My average range for 4 cow elk is 170yds. I used a 30-06 (135 steps) .375 H&H (200yds) .338 (250yds) and a 300WM (100yds) ha. Have a ball friend!