I have a 300 Ultra Mag and just shot it yesterday with Power Level 1 150 gr. Remington factory Ammo. I also shot my .280 loaded with 140 gr. reloads. There was no noticeable difference between the two for me. The .280 is a light Remington Mountain Rifle and the 300 UM is a bit heavier but has a synthetic stock, both have R3 pads. So the 300 is a little heavier because of the 26" barrel. The Power Level 1 does reduce recoil to around the .270, .280 & 30-06 range IMO. Give it a try, I think you will like it.