My 5 port PK is designed for case capacities in the 130 to 160 powder charge range. MUCH larger then the 338 Lapua.
My Medium 3 port PK is designed specifically for chamberings that have 80 to 120 grains of powder charge. This is IDEAL for the Lapua. While the large 5 port may reduce recoil a bit more in theory, you would never feel the difference.
ALso, the large 5 port PK is designed specifically to be used on my Xtreme Heavy Sporter rifles chambered in my 338 ALLEN MAGNUM, 375 ALLEN MAGNUM, 410 ALLEN XPRESS, 458 ALLEN TACTICAL and 50 ALLEN TACTICAL, all based on the highly modified 408 CT parent case.
These rifles are relatively heavy, 17-18 lb standard weight. As such, the 5 port PK is not made with small top ports to control muzzle jump, no need in these larger rifles. The Medium 3 port PK does have three small round top ports to control muzzle jump as they are designed to be used on 10-15 lb class rifles where muzzle jump can be an issue.
As such, the 3 port Medium PK will actually perform better for you because it will control any muzzle jump your rifle produces keeping your eye on target so you can see bullet impact. From a solid shooting position, you will be able to see your bullet impact at any range from 200 yards out.
They will also keep the shooter protected from muzzle blast and ground debris much better then many of the other muzzle brakes on the market because of their slab style, solid bottom design made specifically with the big game hunter in mind. Because of the slab style muzzle brake, they have longer runners in each port which focuses escaping muzzle gas so that there is no high intense 360 degree muzzle blast signature. Its much more focused in the direction of the ports, roughly 30 degrees back from perpindicular of the bore. This does a couple things, protects the shooter better then most brakes and nearly eliminates down range muzzle blast noise. If your 500 yards down range, and do not know the rifle is going to go off, you would have a very hard time being able to tell where the shot came from, IF you even heard it at all.
Generally, if you miss your target, the bullet impact behind them will spook the game toward the shooter because the target has no idea where the shot came from and only hears the bullet smack the ground behind them.
Another thing with the large 5 port, you need a muzzle diameter of at least 0.880" for it to work, the medium 3 port PK works on barrels from 0.675" up to 0.910" in diameter and any caliber from 22 cal up to 416.
Hope this helps. If you have more information go to www.apsrifles.com
All brakes are in stock ready to ship when payment arrives.