Power Factor is a pretty simple means of determining recoil short of rifle weight and powder charge. Looking at Nosler data for the 6.5 x 284 we see that with a 140 gr bullet. up to 2953 FPS is realistic and the Accu-Bond Long Range has a BC of .719 that we'll compare to .338 Lapua Magnum. But first, let's look at recoil. 2953 x 140 / 1000 = 413 PF that most should be able to master and pretty close to the .270 WIN. Just for grins we'll assume same rifle weight.

Going up the scale, since I mentioned it, the .30-06 data shows a max load at 3002 FPS with a 165 gr. Bullet where the Highest BC is .503. PF/recoil would be 495 and a pretty significant jump higher.

Not all snipers can master the .300 WIN Mag where a 200 gr. bullet can achieve 2972 FPS with the highest BC listed at .588. PF/recoil would be 594. I'm simply trying to match velocity of these bullets calibers where in this case a 190 gr. Match Boat-tail might be preferred. That 413 for the 6.5 x 284 looks kinda wimpy at this point.

Now wee see that the .338 Lapua is capable of 2923 FPS with a 265 gr. bullet where highest BC is .778 with PF/recoil at 776.

What we see here is that it essentially takes a .338" bullet at 265 grs. to surpass the BC of the 140 gr. .264". No doubt the .338 will have more energy on impact at a bit more range, but with nearly double the recoil. And with non-expanding Match (FMJ) bullets, KE is not a prime consideration.

Don't mean to steal the Canucks thunder, but with all of the factors that can be calculated with the sophisticated computers available to spotters, that was clearly an advantage. Chris Kyle had a SEAL on over-watch protecting him and that was it. While the Canuck used a weapon with a number of recoil reducing features built into his MacMillan TAC 50 using a bullet almost as 3 x as heavy. To me, you can claim that the Canuck sniper now holds the record, but to me, it's a bit of apples to oranges.