I went on-line in search of recommended minimum arrow energies and penetration criteria.  I found that baseline bow energies begin at around 40 foot-pounds and go up from there. My compound currently has a peak weight of 50 lbs., shoots 185 fps and has 45 ft-lbs of energy off the bow shelf. Is that enough? It depends on your arrow weight and broadhead choice. A light arrow of say 400 grains will lack momentum. Couple this light arrow with a mechanical broadhead or say a three or 4 blade head will offer better cutting but far less or even no full penetration.

On bear, full penetration through both lungs and an exit wound for a blood trail are a necessity.

Under lighter bow and arrow weight, it would be wise to rethink your arrow weight and broadhead choice. Heavier arrows penetrate better as does a cut-on-contact broadhead with a lighter bow weight/arrow weight setup.

The goal is accuracy coupled with penetration by choosing a heavier arrow and perhaps a sharp 2 blade cut-on-contact head to reduce friction.

Accordingly, my 50 lb bow setup (may increase peak weight before the hunt) uses a very heavy arrow of 575 grains for momentum and a two blade cut-on-contact broadhead to reduce friction and maximize an exit wound for blood trailing. Momentum per my Garmin Chrono. note PF- Power Factor is 105.8 KG Ft/Sec. 

I am using a 2219 XX75 with a 2 blade 125g Steel Force head. It shoots like my field points at 20 yards. Reviews of this head for strength are mediocre thus I may try a stronger broadhead. Stay tuned…

Long time big game hunters attest to using heavier arrows given short shooting distances especially on big and dangerous game. 

Good Hunting!