I'v used grin reapers & Tekans, both mechs this year & they killed deer, used thunderheads & cabellas lazer supremes before & they killed deer. The biggest thing is shot placement regardless of the head. They sure seem just as dead with mechs as they do with fixed. Only difference I noticed is they react more with the mechanicals. I think the fixed blade heads zip thru easier causing less pain than the mechs upon impact. Put a big hole thru both lungs tho & they dont go far wether or not they realize they've been shot.