Carl -- There are a lot of "depends" involved. But generally, if you want to be safe and also to shoot accurately out to 20 yards without excessive trajectory, I would recommend whatever it takes to shoot a minimum 650 grains of arrow (Dr. Ashby's minimum recommendation for big-big game) at 150fps. The weight is for penetration, the speed is the slowest that works for me for consistent accuracy out to 20 yards. The only two full pass-throughs I've ever gotten on elk both were with 740-grain arrows, two-blade heads, and 160fps. Both were shot at under 15 yards perfectly broadside, one hit one rib and the other got ribs in and out, and neither animal made it out of my sight before dropping dead. Twenty or so others, using lighter arrows, around 550 grains, and/or three-blades with 64# bows, failed to get full penetration and half-shaft was the norm. All but one required tracking and a few were never recovered, which is a heartbreaker I never want again. Of all elements I would say a heavy arrow -- along with all of Ashby's other recommendatons, including single-bevel two-blade heads, extreme forward balance of arrows, etc. -- that's far more important than speed. Again, what speed gives you in a given weight arrow is flatter trajectory thus more accuracy at longer ranges. And bow weight no longer translates to speed. I have selfbows that draw 65# and shoot only 140, and I have a Lightning longbow that draws 54# and shoots the same arrow 180+. Good luck. dave