Mathews Inc.
NAP Killzone- energy to open
Contributors to this thread:
Bowfreak 18-Aug-17
Bowfreak 18-Aug-17
TJS 18-Aug-17
WapitiBob 18-Aug-17
PECO 19-Aug-17
Butcher 19-Aug-17
TD 19-Aug-17
Bowriter 19-Aug-17
Russell 19-Aug-17
Bowfreak 19-Aug-17
From: Bowfreak
One of the great things about the Killzone is you don't have to worry about them opening in flight. That being seems a lot of energy is wasted to actuate them. I set up a down and dirty experiment to measure how much force was required to open the ones I had on hand and here is what I found:

*Heads 1-3 are all 125 gr. trophy tips with the blades swapped for Low KE blades for a cutting diameter of 1 5/8 minimum measured.

Head #1 -6.0 lbs Head #2 -6.4 lbs Head #3 -6.1 lbs.

*Heads 4&5 were stock 125 gr. trophy tips.

Head #4 -8.0 lbs Head #5 - 7.4 lbs

All heads were measured to the nearest 0.1 lbs per a digital kitchen scale. I can go into more detail later as to my method but even 6 lbs to open seems a little much but 8.0 lbs seems overill.

I love these heads but realized they robbed some oomph from my setup on deer last year. Not to the point of concern but it was noticeable when compared to other mechanical like a Spitfire.

I believe some energy is being wasted on blade deployment as I wouldn't think 6 lbs of force is required to keep them shut in flight. I suspect this has a lot to do with them performing less admirable than Rage on some of the penetration tests I've read.


From: Bowfreak

Bowfreak's Link
I found this article by Curt Wells last night. By his method the Rage 2 blade took 3.2 lbs.

I'm curious if some engineering type could calculate how much force a head must be able to resist without opening in flight when fired out of an average modern setup.

From: TJS
I like these heads! I shoot the 100 gr. coc heads. I did notice the opening to be quite hard. I actually took them apart and flattened the little pressure bump the have on them. Made them open easier. Shot two deer with them last year. First was a 50 yard shot. Not a pass thru but blades did the job with a double lung shot. Second was a 30 yard shot. Devastating hole. Broadhead stuck into opposite shoulder bone.

From: WapitiBob
If you have the desire you could create a force/penetration machine which would give you an energy curve just like a force/draw does for a bow. It'll cost you maybe $750 for Thompson slides, load cell, and xy chart recorder. You'll need to push the heads into virgin blocks of uniform density mtl to have accurate results.

From: PECO
Or you could just forget about it and shoot a solid, sharp, coc head, like a VPA.

From: Butcher
definitely want 70lb with these heads. Shot a doe last year with a 60lb carbon spyder at 25 yards and looked like a tv hit. Was disappointed but probably my fault. I was thinking that a 430gr arrow would still carry enough punch to pass thur. Shot them with a 70 lbs element at 30 and 40 and never not had a pass thur. Going to try the low ke blades this year

From: TD
I think static pressure (energy) and dynamic pressure to open are two different things. A full speed arrow I don't think there will be a big difference from that one and many others. I've only kilt two deer with them (the 2", trying them on your recommendation if I recall, =D if I didn't brainfart that up again) but no real penetration issues.

The broadside doe wasn't much of a test, blew through her like she wasn't there. But on a good sized buck, a hard quartering on shot and a sliver of an angle, entered just forward of straight up the near leg, exited back of the gut and shattered the off side hind leg into about 4 pieces. Maybe, and I mean maybe, one of my favorite fixed 2 blade heads may have gone the rest of the way and laying on the ground.... and a chance, maybe, to not have given up it's life in the effort..... but I was fairly impressed. Buck was on the ground in less than 40 yards.

They might be tougher to open, I don't know. I know I can use them in my regular quiver with all my other heads and they don't open up. Only real issues I've had with them is crawling around with an arrow on the string and you snag one dragging it in the sticks and grass..... they DO open up and are a pain to reset barehanded with one hand.... mostly felt fortunate I NOTICED it had opened.....

From: Bowriter
I can tell you nothing about energy, never gave it a thought. I can tell you, in several years of using NAP Killzone heads, I never had one fail or be anything out outstanding in every aspect. I used them for probably two-dozen whitetails of various sizes and never had a problem. Never had one open when it wasn't supposed to, never had one fail to open when it was supposed to and always-lots of blood and short trails. I now shoot a different head, simply because I get them free and they work great. If I had to buy broadheads again, I would probably buy Killzone.

From: Russell

Russell's embedded Photo
Russell's embedded Photo
Based on two tests, I believe the NAP Killzone penetrates less than the Rage Hypodermic.

The top arrow was shot through a very large mature NY buck from about 25 yards from ground level. Deer was slightly quartering toward me. Arrow passed through one lung and liver. Arrow didn't totally pass thru and was recovered 30 some yards further as the deer entered the swamp. Arrow weight was 418 g and normal diameter.

Bottom arrow killed a mature mountain caribou that was shot 76 yards. Broadside, arrow passed through both lungs and landed 15 feet beyond the bull. Arrow weight was 463 g and small diameter.

Both broadheads weighed 125 g. FOC was a few percent higher on the Rage arrow.

From: Bowfreak
I have never shot the hypo but I do believe that is probably the consensus. There really isn't a huge difference in design but there seems to be a difference in penetration. I am not in the least concerned about the Killzone failing to open. It pretty much has to but being much harder to open than the Rage has to be at least a factor as to why they don't seem to penetrate as well.

I plan to slightly compress the dimple to make them a little easier to open easier. It probably makes no difference but tinkering and trying to reach perfection seems to be a trait a lot of us bowhunter have.....sometimes to a fault.

I have a lot of confidence in this head and am going to have them in my quiver on my upcoming elk hunt. I think the amount of blade you are pushing through an animal is definitely the biggest impedance to penetration but I think being hard to open has to limit at least. The low KE blades are going to be a boost for penetration for sure.

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