The mechanicals work, or open on contact on deer and usually do a good job. Do not go on certain ranches, or certain states, they will not allow them. NONE! Many years ago when mechanicals had gruesome names the hunting pros wanted to try and find if they are worth the extra $$$ I don't remember the numbers but I think it was like 15 pigs shot, only 6 found. After that, the state of Alaska said do not use in this state. Today I still don't know why someone would pay more for bh's when todays fixed bh's are some of the best. Its been said before, if you put the bh through the boiler room, pipes will leak.