.50 caliber is the minimum for elk in Colorado. I have the same dilemna - my son, which I had late in life, is old enough to hunt elk this year. 5'2" and 107 lbs. I took some 348 Gr. Powerbelt and started working down with fffg Triple 7. Got down to 75 grains before accuracy took a dive. Recoil is about like a 20 guage field load.