I shoot the same arrows for moose as I do for grouse/hares.
I wish I had an answer as to why it works, I was skeptical also after seeing birds get up with regular blunts on big game arrows in 60lb longbows hit solidly....still amazes me to this day how tough they CAN be...but that shell casing is an amazing thing! I have shot and currently am shooting some with steel blunts under it...personally I think the steel blunt is way too much weight but it does work. I didnt have any shell casings when I made these up. I dont know if it firms that front end up or just the more foc its giving the shaft is doing it, either way it works and works well! I would NOT use it on tree rats! Try one on a silly chicken or a blue if you have them I'd bet you'll like them as much as we do!
We've done the ground game with bh's they WILL and do fly off from time to time!