Penetration

[Jarrod Reno]

I've  read Dr Ashby's report and searched forums extensively. I had sort of a surprise this week.

I've recently picked up a Toelke Chinook and turns up two very different arrows.

A 533 grain and a 636 grain.

For the heck of it I shot through a local shops chrono and the 533 is moving 207fps and the 636 is moving 196fps. I've now shot these arrows countless times over the past couple days in my block target and a couple 3d's, the 533grain is consistantly penetrating an inch deeper. I would have thought the opposite. Granted I've only been shooting in my back yard at a max of 24 yards.

It's left me scratching my head since I was pretty set and excited to be slinging a 600+grain arrow at close to 200fps but now im leaning towards the lighter arrow.

[pdk25]

Don't confuse penetration into a target with the penetration on live game.  A very different thing.  That being said, if you are shooting the 533 grain arrows that fast, you won't have any trouble killing just about anything in North America, though.  Have fun.

[Jim Wright]

Perhaps you're a bit better tuned and getting  better arrow flight with the lighter arrow

[Sapcut]

Like he said, target penetration has nothing to do with a real animal. I would go with the 636 gr. arrow... without a doubt.

[dustinwittwer]

Is the FOC different on the two arrows? Maybe like Jim said, better tuning, more efficient flight, deeper penetration. I'm building two arrow setups that are very similar to your arrows in weight  (535 grains and 650 grains) out of a 50# recurve, so I would like to hear your results/outcome and what you decide. Thanks for sharing

[Stickbow]

I just got a new Chinook last week and I am not surprised to see your chrono speeds. My 56# @ 29" is a flame thrower with a 500 Grain arrow and flat out dead in the hand. Dan said they performed best between 9 and 10 grains per pound.

Shoot what shoots best they are both plenty of arrow

[Jarrod Reno]

Thanks for all the replys! FOC is a bit more on the heavier arrow, I'll have to measure them exactly but I know they're both over 24%    my goal was EFOC. from what you guys are saying, I'm thinking it must be a slightly different tune. More tinkering to come.

[katman]

Same shaft diameter?

[Jarrod Reno]

Yeah, same diameter, both micro diameter (don't shun me!    

Both Victory VAPs

250 (90-105lbs) spine for the 636gr & 300 (70-90lbs) spine for the 533gr

Changing dynamic spine with points/inserts. Because of the micro diameter it's technically closer to center.

Definitely an unorthodox arrow set up but comparing the VAPs I shot last year with my Caribow compared to a very similar GT, penetration with the VAPs was 4-5inches deeper, granted, that was on a brand new block target which I realize is different then shooting through an elk.

[old_goat2]

Yeah, either one is plenty for North America with the right broadhead, the heavier one will be easier on your bow and quieter and still way faster than what most folks get!

[KentuckyTJ]

Originally posted by Jim Wright:
Perhaps you're a bit better tuned and getting  better arrow flight with the lighter arrow

Yep, its flying straighter!

[DanielB89]

Originally posted by Sapcut:
Like he said, target penetration has nothing to do with a real animal. I would go with the 636 gr. arrow... without a doubt.

Why?  

the 533 grain arrow is PLENTY of arrow.  Not to mention the extra speed he gets which will help with longer shots, etc.  


Though I don't agree with all he says, i did stumble upon this a few years back.  

 

 


no explanation needed, just simple tests ran with different weight arrows and the same broadhead.

[Bladepeek]

I had an interesting experience at the Michigan Longbow Assoc Spring Fling this year. I've been working with some EFOC arrows and took two of them with me - one fletched and one bare shaft.

Now, I'm only shooting a 46# bow. I have some 1535s that are well tuned to the bow with 175gr points and standard 11gr alum inserts. I also have the EFOC 5575s with a total of 400 gr up front (300 gr point and 100 gr inserts) that are flying quite well. We shot them both into some hay bale backstops and into an earthen bank.

I expected to see those 400 gr EFOC arrows penetrate MUCH deeper than the light ones, even though the lighter arrows were flying faster. They didn't - about 1 1/2 - 2" deeper was all.

Now I agree field points are going to act differently than sharp broadheads, but I'm also thinking there is a point where increased momentum can no longer make up for loss of kinetic energy. If I were shooting a 2000 grain arrow out of this 46# bow, I doubt seriously whether it would penetrate very deeply at all.

Where's the point of maximum penetration? Darned if I know, but I do believe strongly there is a point of diminishing returns where weight gains you no more in penetration. A point where the speed drops off so far, it's more than just a question of trajectory, but also loss of penetration. Obviously, if you're shooting 80# bows, that weight is way up there somewhere, but the principle is the same.

I guess the older I get, the more "middle of the road" I become.

[pdk25]

Originally posted by DanielB89:
 

Originally posted by Sapcut:
Like he said, target penetration has nothing to do with a real animal. I would go with the 636 gr. arrow... without a doubt.

Why?  

the 533 grain arrow is PLENTY of arrow.  Not to mention the extra speed he gets which will help with longer shots, etc.  


Though I don't agree with all he says, i did stumble upon this a few years back.  

   

   


no explanation needed, just simple tests ran with different weight arrows and the same broadhead. [/b]

Not sure if you were referring to my comments, but friction targets really don't simulate live targets well.  I also suspect some tuning issues are at play.

[monterey]

Bladepeek, I think your 1.5 to 2 inch increased penetration is significant considering the medium you shot into.  That would probably translate to much more penetration in game.

A dirt bank is a major stopper.  Even bullets that may easily penetrate the length of a deer or elk will stop within a few inches in a dirt bank.

[Bladepeek]

And the hay bale? I agree dirt is not muscle and a field point is most definitely not a sharp broadhead. There will be a point, however, where increasing weight will not increase penetration. I don't know where that point is, but eventually you will reach a point where it is similar to a BB and a cannonball. As long as you have sufficient power to throw that cannonball, it will smash through things the BB will not even dent. Once you reach the point where the cannonball overpowers the propulsion to the point where it is barely moving, it won't penetrate as deeply as the BB.

I'm not saying I've reached that point, because the EFOC, heavier arrow obviously penetrated farther. I'm just saying I believe a point exists where more weight will penetrate less.

[monterey]

I'm just saying I believe a point exists where more weight will penetrate less.
 

That's something that is well worth consideration.

When I shoot into foam with a 43# LB and arrows weighing 420, 525, 600, 650 and 675, I see a steady progression of penetration as the arrow gets heavier.

[Trond]

Throwing my self in here. Given that the only factor changing is the weight of the arrow, the heavier the arrow gets, the faster it will lose speed. This due to it's aerodynamic resistance. So there will be a point where the lighter arrow will have more momentum and penetration due to higher speed, but the distance travelled must be a part of the equation.
My two cents...

[Sam McMichael]

It sounds like both of these arrows will serve your purpose very well. Which one do you shoot more accurately? That's the one I would use.

[ozy clint]

one can only make reliable conclusions when comparing results with only ONE variable. that seems to have been forgotten here.

trond- resistance increases with velocity, EXPONENTIALLY. so the faster arrow slows down faster.

it's all in the ashby files.

blade peek- there is a point where increasing weight will decrease momentum. think of a bell curve. with added mass momentum goes up till the top of the bell curve is reached then it starts to go down again because the same energy is being applied by the bow.
what your thinking isn't comparing results with only one variable. your comparing arrows of different momentum values.
yes the arrow at the top of the bell curve will penetrate more than one thats gone past the top of the bell curve, not be cause it's heavier but because it's got less momentum.

you need to compare arrows that are at the same level either side of the top of the curve. both have the same momentum but differ in mass and velocity. the heavier one will penetrate more because it encounters less resistance because it's slower.