WolfKiller---I wouldn't worry too much about 100grn heads versus 125grn heads. Those Muzzys will bring an elk down with no problem. My son and I both shoot Gold Tip carbons with Muzzys on the end. Difference is he shoots 5575 GT with 100grn 3blade, he setup is right at 400grns. He's taken 5 bulls with that setup, all pass throughs. I on the other hand shoot 7595 GT with 125grn heads at about 425grn, I too have had the same success on elk with that setup. To see a real penetration difference with a like setup you'd have to go another 150grns heavier to see any significant penetration difference. I'd stick with 400grn minimum and hitem where they live, you'll do great! Good Luck--ElkNut1