metro

Bought a new bow today, 06 Bowtech Allegiance

It chrono'ed at 301 pulling 65 lbs. 29 inch DL and arrows weighing in at 347 grains.

The shop owner told me that these arrow weights would be fine for taking pigs, white tail deer, coyotes etc... But I would need more mass for bigger game such as elk.

If you have arrow speed with a good sharp broadheadand you get a pass through is'nt the kill due to the vitals being punctured?

What is need for more mass? Isn't it all the same?

50mass X 30 speed = 1500KE is the same as 30mass X 50 speed = 1500KE

NY eXtReMe

Thats 70 Lbs of KE, your fine.
http://www.bowsite.com/bowsite/featu...tion/index.cfm

mobow

Yes, but you may be lacking in the momentum department. KE is figured at the bow, not down range. A heavier arrow would retain that speed longer. A light arrow will slow down quickly. While 70# of KE is good, and will probably kill anything you would shoot at.

I am not sure what formula you put up, I've never seen it, but that's no indicator of anything except that I've never seen it. KE=speed x speed x weight / 450,240.

Arthur P

It's not all the same, metro.

A heavier arrow takes a bit more energy from the bow. Usually only 2-3 ft lbs, so it's not much, but it can make a big difference in how long your bow lasts. It's just that much less energy left for the bow to absorb, to cause extra noiseor to makescrews and boltsvibrate loose. I think a bit heavier arrow is more pleasant to shoot, because it's just that much less energy left in the bow to be transmitted to your hand. Or make you have to buy expensive rubber doodads to help absorb the vibration.

But as far as hunting bigger game goes, the heavier arrow not only takes a bit more energy from the bow, it also carries it's energy better downrange.Thehefty arrow hits the animalwith considerably more energy than a light arrow does, making for deeper penetration.

Dr. Ed Ashby has donelong term research on arrow lethality, first on large African game and is currently doing another study on Asian buffalo in Australia. He and I are in complete agreement that arrow momentum is a much better tool for predicting depth of penetration than KE is. Another school of thought is that KE is a better indicator. A heavier arrow from the same bow will carry more energy AND momentum though, so no matter which side of the fence you are on, the heavier arrow wins.

For thin-skinned medium size game, the light arrow has proven it is effective. Some guys have also done well on elk and such with their light arrows, but I believe they take unnecessary risks doing that. A bit of a bad hit, poor penetration, and they've got a wounded animal to track. A heavier arrow is good insurance because it will penetrate deeper in all circumstances.

I think a good parallel is with bass fishing. Some guyslike to fish for largemouth bass with ultralight tackle and have proven big fish 'can' be taken with 2-4 lb test line. But pro fishermen, who have to put fish in the boat to get a paycheck, use much stouter equipment. Guys who want to be sure they've got a bit extra oomph when the arrow hits, for better penetration on larger animals, they use heavier arrows.

Now, you 'can' ramp up momentum with speed as well. For example, a 350 gn arrow at 300 fps carries the same momentum as a 700 gn arrow at 150 fps.However,Dr. Ashby has concluded that all momentum is not the same either. He says momentum gained through arrow speed is not nearly as effective as the momentum gained through arrow weight. He's spent many years doing research in the field, on actual animalflesh and boneinstead of poking arrows into foam targets, so I tend to believe his results.

I believe a very old rule of thumb is just as valid as it was many years ago. For hunting, use the heaviest arrow that will give you acceptable trajectory. Don't use the heaviest arrow you can get. Don't go with the flattest trajectory you can get. Balance the two.

Archery has always a matter of trade offs - sacrificing one thing to get another. Contrary to popular belief among the speed cult,none of the technology that has come along has changed that, nor will it ever change that. They use ultra light arrows to get the fastest speed and flattest trajectory possible. What they trade for that is shorter bow life, more expense (those rubber doodads I mentioned earlier, for example), more bow noise... Not to mention having to buy a new bow every year or two just to stay on the raw edge of performance.

Whether that's smart or not, I'll leave it to you to be the judge.

davidmil

Not only will you get better down range performance from a heavier arrow, you'll also get a much quieter bow to shoot. You're a big boy, give up a few fps, add about 100 grains to your arrow weight and you have really got something with that 29 inch draw. I might even try to beef the poundage 2 or 3 pounds to help hold some speed. You want to be a speed freak on the range...fine, but for hunting and shooting broadheads I'd go the other way.

metro

Thanks guys especially Arthur, that was very informative. My goal is hog hunting this late spring and summer when I move to Texas. So right now my main goal is to get this bow dialed in, I have already noticed it is much less forgiving than my TomKat. I like the smoother shooting, quieter, less shock train of thought so I think I'll take Davidmil's advise and bump up 100 grains. I just need it to be fairly flat shooting out to 30 yards or so.

Sylvan

metro,
Anyone who knows me knows I'm always advocating to error on the heavy side as far as arrow mass is concerned.A heavier arrow always delivers more "punch"but in your case imo you've got a lot of"punch"to spare. To put it in perspective I took your conditions and scaled it down to 55 pounds peak weight but increased the arrow mass to 600 grains. The new calculated values are 65.2 ft/lbs ke and 0.59 pound seconds of momentum. Almost everyone would agree that 55# and a 600 grain arrow launched with 65.2 foot pounds of ke (that's221 ft/sec)is more than adequate for any elk or even moose. Now if that is adequate, your setup outperforms this one both in ke and momentum right on out past 50 yards. So in other words you are delivering more "punch" by any measure be it ke or momentum than the same bow set up at 55 pounds peak shooting a 600 grain arrow at virtually any practical hunting distance. Anyone who agrees that 55# peak and 600 grain arrow will do the job can't argue about your setup even with the 347 grain arrow.

I hope this little exercise helps...

ButchA

Metro,

Try this link.... It's from a site called "Prairie Shack". They have all sorts of fps speed calculators, KE tables, etc...etc...etc... It's a pretty cool site.

http://www.prairieshack.com/

Arthur P

I won't argue that, Sylvan, but put that 600 gn arrow on his bow at 70 pounds and I know youwouldn't argue that itcan't do better than the 347 gn arrow. Especially when he's talking about some of these mud-caked, thick skinned, 300-500 poundTexas hogs.

Oh, and while you're at it, calculate the midrange trajectory for both arrows at 30 yards and tell us what you come up with.

Sylvan

There is no question that a heavier arrow shot from the same bow will deliver more of both ke and momentum and at any range. A heavier arrow shot from a bow set at 5 pounds more peak weight will deliver even more. Whether or not it can "do better" is a bit more complicated question.

If we stick with my original comparison for a moment and say that the 55 pound 600 grain example will deliver enough "punch" for a consitently clean pass through at hunting ranges then most certainly the 65 pound 347 grain example will pass through as well as it delivers more "punch". Now the 70 pound 600 grain arrow will obviously deliver more of both ke and momentum than either of the previous 2 examples so most certainly will result in pass throughs as well.

There will be2 differrences. 1) The 70 pound 600 grainexample caculatingto 249.6 ft/sec will follow a slightly more arched trajectory to its target than the65# 347 grain example and a slightly less arched trajectory than the 55# 600 grain example. 2)After "passing through" the animal itwill strike the ground with more "left over" energy than either of the 2 other examples.

So does it "do better"?Wellimo, it makes no differencehow far an arrow penetrates the ground after passing through an animal soif the measure is damage done to the animal thenclearly it has no advantage on that count. It does howeverfollow a slightly more arched trajectory than the 347 grain arrow so on that count it doesn't do quite as well. So given the facts you tell me.

IMO, more ke and momentum is "better" only to a point. Once you start driving arrows deeper and deeper into the ground after passing through, more energy is only wasted and that wasted energycould be used to flatten trajectory.