Im not familiar with the 338 mega, Ive been shooting a 338 win since 75, and a 338 Lapua improved since 95, I've taken and used the Win in Alaska Africa Siberia and all across the western us, in the Win I've used and harvested animals with the 160 185 and 225 gr Barnes, as well as Nosler 200 gr BT the 210 and 250 gr partitions and the 250 gr sierra, in the bigger lapua I started with the 225 gr accubond but I didn't care for the way they came apart at the higher velocity (3360 Fps)under 200 yards, so I switched to the 185 and 225 gr Barnes x, both weights shoot to the same point of impact at 100 yds in my rifle anything bigger than deer I use the 225 gr, if I had to give one up, it would be the Lapua, even though I built it for long range hunting I find the 26in barrel and heavier weight of this rifle is not well suited to timber hunting, with my style of hunting I'm just as likely to encounter a animal at 50 yards or less than I am finding one over 500, my Win with its 21 inch barrel and its 2'5x8 leupood tip the scale at just over 6lbs, I know the popular trend these days is with the heavier bullets, however I've never felt I couldn't get the job done on anything when using a 225 or 250 gr bullet, the longest shot I ever made was a shot I had no business taking, but I let the poor judgement of youth get in the way of common sense, A single 250 gr Nosler partition through the pocket on a Colorado rag horn did its job, the bull tried following the herd but only made it about 50 yards before expiring, I know the win round is not considered a long range round, however a 250 gr slug in the right place will get the job done and has never let me down,