passthru79

it is true that momentum does play a role in trajectory but Im pretty sure that the increase in speed from a 460 grain arrow 2 a 360 grain arrow would make up for it.

sctf520

I'm new around here but I started reading this thread and found it most interesting and intruiging. I've been into archery for about 30 years and never really considered most of what I have read here, so I thought I would try a little experiment of my own. Bow= 07 Bowtech Allegiance 27"dl @ 59.5 lbs. dw, arrows= 27" goldtip ultralight 400's at 300 grains on my digital scale and 28" goldtip ultralight 22's at 350 grains with same vanes and points with similar spines and FOC'S. Shot arrows at 20, 30 and 40 yards, 6 of each arrow at a newmorrel cube at each distance and I mixed up the arrows just for fun. At 20 yds. arrows all grouped together, at 30 yds. arrows all grouped together and at 40 yds. guess what? all arrows grouped together and there was very little differance in penatration.I realize that 50 grains isn't that much different but I was still suprised at the results. Is this apples to apples or did I screw something up.

davepjr71

You didn't screw anything up. Fifty grains just isn't that much of a difference to matter.

When I did my test with 391 gr arrows and 512 gr arrows at 20 yds they had the exact same impact point. However, the 391's had better penetration by an average of 2". Ashby's test enlightened me on why that was the case. Contrary to other poster's beliefs that the heavier arrow will always out penetrate the lighter one, the lighter arrow has an FOC in the neighborhood of 18% and the heaver arrow's FOC is around 12%.

Ashby's tests prove that a higher FOC light arrow will out penetrate a lower FOC heavier arrow by as much as 50% in some tests.


TFOX

You should be a moderator.

bowhunter44

In regards to following Ashby's tests. If we all went along with the status quo we would have never figured out that the world was round!!! You are really giving an argument for sticking with the world is flat than round with the way you said that. Therefore, I'd rather keep trying to discover something new then follow everyone else like cattle.

Sorry I'm not aswell spoken and loquaciousas you and made that sound more condescending.

Straightarrow

With that information, I guarantee you spine was not right for both arrows. The chart is a guideline. It doesn't mean that every arrow in that range will have perfect spine. To get perfect spine you have to match arrow length and/or draw weight to your exact setup. A given arrow length will only have an exact spine match at one particular draw weight when shot out of a particular bow.

If you want to prove this to yourself, shoot them both bareshaft at 20 yards and you will see that both will not enter the target straight on. Only a correctly spined arrow will enter perpendicular to the target.

Straightarrow

We've already mentioned it several times in this thread, but it was probably not noticed because we we referring to retained energy down range. Retained energy comes in the form of speed. The heavier arrow loses speed at a lower rate. It also explains why a heavier arrow doesn't slow down as fast when it enters animal, which equals greater penetration.

Straightarrow

The status quo is to go for speed. It's what 90% of everyone is trying to do. It's what drives manufacturers, and most advertising. The thing about Ashby's testing is that it's real world data from shooting live animals. The "speed is better" crowd has no credible data that shows greater penetration in live animals. Point me to a single study no matter how small. Ashby has spent the better part of 20 years looking into the stuff. He has performed hundreds of tests and experiments. He has spent over $300,000 of his own money in the search for answers. His tests include many hundreds precise measurements on equipment and penetration results. He used all types of bow, arrows, and broadheads. He compiled all the data into easily deciphered charts, graphs and written explanations. Please, point out a single conclusion he came to and tell me what he did wrong to come up with that conclusion, and why you're right.

You appear to be saying, ignore that garbage. Fast, light arrows penetrate better because.....? Actually, I still don't know what your argument for speed is. Maybe you can be more clear. Exactly why is a light arrow better than a heavy arrow for shooting live animals at hunting distances? Are you saying that a light arrow penetrates as well as a heavy one or better?

I've said it before and I'll say it again, the need for speed came from the 3D crowd who wanted to hit a 12 ring without knowing the distance. The goal of a hunter is to penetrate to the vitals, no matter what gets in the way. A night and day difference in goals. A night and day difference in what equipment is needed to accomplish those goals. Trouble is, hunters started playing 3d and forgot what they were trying to accomplish. Manufacturers took it and ran with it, and now huge percentages of hunters are brainwashed into thinking the most speed possible is what's important. The brainwashing has been so effective that bow shops promote it (gotta buy that new faster bow) and hunters defend their beliefs with no evidence that their light arrows are the best for taking down game.

Arthur P

Going for 30, TFOX? Okay, we'll work on it. [8D]

From the ballistics calculator at www.bowjackson.com

Momentum is not calculated in slug units on the program, so you'll need to convert the numbers yourself if it's that important to you. It really upsets me to no end that Andrew Middleton's graphing trajectory calculator is no longer available on-line. That was a nifty program, excellent for making sight tapes. Anyway....

A 350 gn arrow at 300 fps - 30" shaft, 4" feathers, .310 arrow diameter

0 yards - 300 fps 70 ft lbs .4655493 lb-sec momentum
10 yards - 292 fps 66 ft lbs .4534967 lb-sec
20 yards - 285 fps 63 ft lbs .4421170 lb-sec
30 yards - 277 fps 60 ft lbs .4303314 lb-sec
40 yards- 270 fps 57 ft lbs .4192708 lb-sec

450 gn arrow at 265 fps (to achieve equal KE at launch. KE would actually be a couple ft lbs higher with the heavier arrow, but just so we won't have any griping about apples and oranges... [8D])

0 yards - 265 fps 70 ft lbs .5287310 lb-secs
10 yards - 260 fps 67 ft lbs .5183532 lb-sec
20 yards - 254 fps 65 ft lbs .5076107 lb-sec
30 yards- 249 fps 62 ft lbs.4974557 lb-sec
40 yards - 245 fps 60 ft lbs .4878741 lb-sec

How about something I'm more likely to use, say a600 gn arrow at 229 fps?

0 yards - 229 fps 70 ft lbs .6092045 lb-sec
10 yards - 226 fps 68 ft lbs .6000703 lb-sec
20 yards - 222 fps 66 ft lbs .5914318 lb-sec
30 yards - 219 fps 64 ft lbs .5826874 lb-sec
40 yards - 216 fps 62 ft lbs .5745283 lb-sec


By the time they've gone 100 yards - just for giggles, not suggesting anyone shoot at game 100 yards off with a bow - the 350 gn arrow is down to 234 fps and 42 ft lbs. The 450 gn arrow is at 220 fps and 48 ft lbs. My 600 gn arrow? Oh, it's loping along at 202 fps and 54 ft lbs. Now, isn't that something? That350 gnarrow is only 32 fps faster and carrying12 ft lbs LESS than the 600 grain arrow. Who'da thunk it?

The lighter, faster arrow with less momentumlost30 fps in speed, 13 ft lbs in KE over 40 yards. The heavier arrow with more momentum lost 20 fps and 10 ft lbs in KE over the same 40 yards. The 600 gn log with even more momentum lost only13 fps and 8 ft lbs over that 40 yards. This is pretty good proof of what I've said many times, that light arrows can't even penetrate AIR as well as heavier arrows.

The higher the momentum, the more velocity and KEare retained downrange, where penetration occurs. (Hence my point of view that usinglighter arrows for flat trajectory at longer distances is a poor thing to do. I say use heavier arrows and a freakin' RANGEFINDER!!) By the same token, the higher the momentum the more KE and velocity are preserved as the arrow is going through flesh and bone.

The more KE and velocity are preserved during penetration, the better chance for complete passthrough, with two leaking holes for a better blood trail. Or, at least, a better chance of achieving penetration into the vitals when things don't go as intended.

Not to mention that heavier, slower arrows have slightly more time to stabilize between the bow and the target, so they're more likely to be flying straight when they make contact on shorter distance shots. They are easier to tune. It's much easier to tune broadheads to them and you can use bigger broadheads for more tissue damage and even better blood trail.

Heavier = better when it comes to penetration. Period.

What galls me about this whole thing are these 'minimum KE charts' you see popping up here and there. Some of them put the minimum KE so high that a traditional shooter wouldn't be able to hunt larger game, likemoose for instance,with even an 80lb bow. In reality, many a moose has fallen to recurves and longbows pulling no more than 60 lbs with heavyweight arrows.I believeminimum KE charts arecompletely wrong and area threat to bowhunting and need to be eradicated. There is no way to establish such a chart without also considering arrow weight, FOC, shaft diameter, momentum, broadhead design....

This is especially so now that KE is proven to be only a supportingcomponent of penetration potential. The prime componentis momentum. That's what determines how well all that KE is preserved during arrow flight and during penetration.

Straightarrow

I forgot to address this, and it's very important. Ashby found that high FOC increased penetration, but extreme FOC increased it by a greater percentage. In fact, it wasn't until he reached 27% FOC that the percentage went way up.

The other point - none of his high FOC arrows were light. How do I know this? Try building one. I've built up many. To get the FOC up to 20% or higher, requires a very heavy tip. How heavy will depend on draw weight, draw length and shaft stiffness. When you increase tip weight, you also now need a stiffer shaft. I challenge you to build an arrow with a an FOC of 20% or greater that is shot out of a 70 lb draw, draw length of at least 28", arrow length of at least 29", with the proper dynamic spine and keep it under 600 grains . Ashby's high FOC arrows are not light, not by any stretch of your imagination. Most extreme FOC arrows shot out of a 70 lb bow are going to be in the 800-900+ grain range.

Straightarrow

And to add to that a bit, Ashby also found out that when momentum was obtained through mass vs speed, the arrow with the greater mass penetrated further, even though momemtum of the faster arrow was equal or greater. The real key is to obtain penetration with weight. Putting that weight on the tip is even better. However, without the weight, penetration suffers.

So, adding to Arthur's example, his heavy arrow not only has much more momentum, but that momentum is much more effective at penetrating because it was obtained through more weight, not more speed.

bow_hunter44

OK, I give up. I though the original tentant of this thread was something of a breach with the status quo (current status quo being defined as speed, speed, more speed, blazing speed),to consider something other than, although in addition to,Kinetic Energywhen evaluation arrow performance. Oop, silly me. Sometimes I miss theseemingly obvious.

Additionally, I thought one of the fundamental tentantsof science was the continutal pursuit of improving current theories. Dr. Ashby's work is, if nothing else, scientific. I could have swonr that I said something to the effect that 'I will use his work as a resource until something better comes along'.At the moment Dr. Ashby's work is the most significant scientific body of work (that I am aware of) in the world regarding terminal arrow performance. If that belieflabels me asdemonstrating herd like behavior, so be it.