Mechanical Broadheads and Kinetic Energy

[Sharp Things]

Don't confuse the actual work required with initiating the opening of the blades and fully deploying them with resistance perpendicular to the line of action. If a mechanical doesn't penetrate deep, there are other factors involved. Pushing a mechanical into anything slowly and by hand to watch a scale or gauge for "opening force" is not the same thing as it traveling at 265 fps. Back in the day, the famous test was pushing a piece of stretched elk hide over a stationary broadhead fixed in a vertical position to test (or to refute the validity of mechanical's, and at the time it was the Punchcutter) which broadhead took the less force to penetrate. It was one of the biggest follies of tests ever done and didn't prove a whole lot.

The punchcutter's, spring plunger tip and ridiculously poor and flat cone followed by a lengthy and unbladed ferrule were most likely the reason for the poor performance on elk hide. Ive also done the test using the punchcutter along side a long list of other fixed and mech heads. There is a good reason the punchcutter is no longer in production. It was crap.

That said, slow speed tests in which all the heads are evaluated using the same means and media is a useful way to gauge breaching force in a comparison from head to head. Certainly, real world speed translates into better performance but since some folks will try to push that head through an elk with a 350 grain arrow and others will use a 700 grain, arrow, results will vary in the real world as well.

 

[Sharp Things]

So you confirming that lack of mechanical advantage in the head has as the determining factor? For example would a open rage head performed just as poorly because of its poor design(bad blade position and angle and lack of leading cuting edge)?
The “opening” isn’t the culprit so much as what it opens too. Witness the slick Trick.

The tip sharpness, the distance from the tip to the point that blades actually begin to cut, the degree of sharpness, the ability to retain that edge (a product of the bevel grind and steel quality) and blade angle (ramp) all factor into penetration. If you are referring to a test in which mech heads in the "deployed" state are evaluated side by side with fixed blade, cut on contact heads, I can assure you the fixed blade cut on contact heads will require less force to penetrate in a constant medium.

 

[Trial153]

If you are referring to a test in which mech heads in the "deployed" state are evaluated side by side with fixed blade, cut on contact heads, I can assure you the fixed blade cut on contact heads will require less force to penetrate in a constant medium.

I am not referring to this at all.

The premise of the OP question was the force required to open the heads being a deterrent to performance.
So we have to compare the same head with your test open and closed to measure how much of factor the “ opening “ of Head is determination of the force needed. My point and experience tells me that because of the poor design, ( all you stated above ) the opening of the blades is negligible compared to same head already in the open position. It’s not so much what it takes to open as to what it opens to.

 

[Sharp Things]

Ok, I agree and understand what you were asking. That is why I stepped away from mech heads. The deploying is a negative in my eyes as it runs counter to what I want from a head and as you stated, the "what you end up with once open" was another reason I scrapped mech heads. The poor and thin and weak blades were another reason.

All that said, its clear the mech heads are a popular choice (I contend mostly because people dont take the time to tune their gear to make every broadhead fly like a filed point) and they kill lots of animals but the lack of penetration causes me to shy away. All the game I killed with Rage heads died so clearly they worked for me 100% of the time but none were pass throughs. at the same time, there are those that love and swear by them so for them, they are a perfect choice and confidence in your gear is pretty important.

 

[Nick Muche]

I don't shoot mechanical heads for their penetration ability, I shoot them because they are devastating to the game I hunt and have produced very short and very easy to follow blood trails. Though, more often than not, I get a pass through, I'd say over 90% of the time.

 

[Sharp Things]

Yes, many folks swear by them and its clear they are responsible for the deaths of pretty much every species. I tried them. they worked but there are just so many good heads on the market and I like to try a lot of them. The failure rate or the failure potential compared to a quality fixed blade head has me going with fixed blade, high quality steel. Also, I huntin with a low poundage trad bow for certain species and I would not consider a mech head for that weapon but across the board I can use the well made fixed head regardless of the bow Im shooting at the time. Its really just a personal preference thing in my mind. The kills I had with rage worked even if the heads were not reusable afterwards (something else I value in a head)

 

[Gumbo]

I had a season of poor penetration on good shots with mechanical heads (hypodermics) in 2016. I smoked an elk in the lungs at 53 yards, got poor penetration and no blood trail. I also stuck an antelope in the lungs at 43 yards with very poor penetration. Could that have happened with a fixed blade? Of course. The only reason I wanted to run them was forgiveness in tuning and shooting. I then began shooting them again in 2017 broadhead practice and wasn't very excited about their grouping. I tried some Ramcats, which actually grouped better than the mechanicals and shot almost spot on out to 60 with my field points after a very slight rest adjustment. That sealed the deal for me.

For what it is worth, I got far better penetration with the Rage SC broadheads, which I think is due to the blades on the tip cutting a hole rather than the poking tip of the hypos.

 

[MattB]

I think some folks nailed it in suggesting a static vs dynamic test for determine how much energy a MBH takes to deploy or penetrate hide isn't representative

 

[bojangles808]

I had a season of poor penetration on good shots with mechanical heads (hypodermics) in 2016. I smoked an elk in the lungs at 53 yards, got poor penetration and no blood trail. I also stuck an antelope in the lungs at 43 yards with very poor penetration. Could that have happened with a fixed blade? Of course. The only reason I wanted to run them was forgiveness in tuning and shooting. I then began shooting them again in 2017 broadhead practice and wasn't very excited about their grouping. I tried some Ramcats, which actually grouped better than the mechanicals and shot almost spot on out to 60 with my field points after a very slight rest adjustment. That sealed the deal for me.

For what it is worth, I got far better penetration with the Rage SC broadheads, which I think is due to the blades on the tip cutting a hole rather than the poking tip of the hypos.

the angle on the hypos when depolyed hurts their penetration power imo. i prefer killzones for rear deploying as the angle isnt as steep, but i only hunt deer sheep and goats.

 

[rcb2000]

I think its safe to say a 'jackknife' style opening on a mechanical will suck up momentum more than a rear deploying.
I shot a deer last year at 30 yards with a grim reaper, (28" DL, 65# DW) and although it was a devastating hole through both ribs, it didn't completely pass through. Not a huge deal, but it ran off with the arrow through it, so didn't get an immediate blood trail. What did happen, was a ton of blood pooled up in the thoracic cavity before the arrow broke off, then started to get a great blood trail.
I am considering a rear deploying Rage S/S this year.
I'm also going to have 1-2 arrows tuned with a Slick Trick in the quiver, as there is always a time when I need to punch through brush or might clip a branch.

 

[Blockcaver]

I'm also going to have 1-2 arrows tuned with a Slick Trick in the quiver, as there is always a time when I need to punch through brush or might clip a branch.

rcb, Arrows don't punch through brush and stay on course in my experience. You get deflected and miss or worse. Wait for a better shot where there is a clear opening to the critter. Good luck bowhunting!!!

 

[Beendare]

I think that if a guy is going to use mech heads....he just needs to consider his whole setup accordingly. So in other words, use a sufficiently heavy arrow to make the head itself more effective.

There are many reasons why I went away from mech heads...but there is no denying they work.

 

[rcb2000]

rcb, Arrows don't punch through brush and stay on course in my experience. You get deflected and miss or worse. Wait for a better shot where there is a clear opening to the critter. Good luck bowhunting!!!

Solid advice, thanks!