Broadhead Weight: 100 vs 125 vs 150 Grain
Broadhead weight is the fastest way to shift FOC and change how your arrow behaves on impact without touching the spine chart. 100 gr is the compound-bow default. 125 gr adds forward weight for penetration on bigger game. 150 gr and up is the heavy-arrow, Ashby-influenced crowd chasing bone-splitting KE on elk, moose, and buffalo.
Kinetic energy math you can trust
A 450 gr arrow at 280 fps produces about 78 ft-lb of KE. Swap the 100 gr head for a 125 gr head and you drop to 273 fps but total arrow weight climbs to 475 gr, giving 79 ft-lb. FOC also climbs from about 12 percent to about 15 percent. Slower arrow, tighter groups at long range, better penetration.
Scenario 1: whitetail, 60 lb compound
100 gr Slick Trick Magnum on a 425 gr total arrow at 280 fps gives 74 ft-lb, well above the 40 ft-lb whitetail threshold. Zero reason to add weight. Faster arrow, flatter trajectory to 40 yd.
Scenario 2: elk, 70 lb compound
125 gr Iron Will S125 on a 500 gr arrow at 275 fps gives 84 ft-lb, above the 60 ft-lb elk threshold with margin for shoulder hits. This is the modern western hunter setup and it works from Colorado to Idaho.
Scenario 3: moose or buffalo, 70+ lb
175 to 200 gr single-bevel (Cutthroat, Grizzlystik Maasai) on a 650 gr arrow at 240 fps gives 83 ft-lb. Slower on paper but drives through both shoulder blades because of FOC and heavy tip weight. This exceeds the 70 ft-lb moose recommendation.
Went from 100 gr to 125 gr Iron Will 3 years ago on elk. Arrow dropped 10 fps, trajectory shifted 2 in at 40 yd, penetration on shoulder went from partial to complete pass-through. Never going back.
Archery Talk, Elk Hunting Forum, 2024
Broadhead law by state
Fixed blade: Legal in all 50 states for big game archery seasons.
Mechanical: Legal in ~44 states for big game. Restricted or discouraged in Idaho (mechanicals prohibited for big game archery), Oregon (mechanicals prohibited), and check current-year Wyoming regs. Legal but not preferred for elk and moose where cut-on-contact fixed heads penetrate through heavy shoulders.
Cut-on-contact: Legal in all 50 states. Preferred or required in some traditional-archery-only hunts.
Minimum cut diameter: Most states require 7/8 in cut for big game. A handful (Georgia, Mississippi, others) require 1 in. Always confirm current-season regs with your state fish and wildlife agency.
Blade count: Some states specify minimum 2 sharpened edges. Most modern broadheads exceed this by default.
This is a research summary, not legal advice. Confirm the current season regulations with your state fish and wildlife agency before you buy or hunt.