Straightarrow

7 grains per inch is a pretty light arrow. 7 grains per pound would be a much better choice for most people. I'm not saying that you aren't hitting where you're aiming. It has been proven time and time again that a very poor flying arrow can hit the same spot each time. Your arrow may be flying perfectly, but you won't know just because it's hitting where you're aiming.

That's a 5% increase in K.E. I doubt that will be noticable in the field.


Personally, I've seen very few hunters who actually tune their bow for perfection. Most of the ones I've observed do a very half-baked job. I do agree that it's a good idea to try to get your arrow to perform it's best. I just have a different definition of what is best. I don't think tuning for speed or KE is best. I think arrows should be tuned for the best possible flight. This can be done on many medium weight arrows and lots of heavy weight arrows, but is much more difficult on very light weight arrows shooting fixed blade broadheads.

NY Hunter

I've crunched the numbers for a lot of friends bows and anything from a heavy,slow arrow to a light,fast arrow will yeild the same KE numbers (per the formula) on the same setup. You must change draw weight or draw length to change the KE numbers for a given bow. That's the math... I would rather have the heavy arrow hit the deer,but the mathmatical numbers come out the same.

NY Hunter

I've crunched the numbers for a lot of friends bows and anything from a heavy,slow arrow to a light,fast arrow will yeild the same KE numbers (per the formula) on the same setup. You must change draw weight or draw length to change the KE numbers for a given bow. That's the math... I would rather have the heavy arrow hit the deer,but the mathmatical numbers come out the same.

MilDotMaster

[quote]ORIGINAL: Straightarrow

7 grains per inch is a pretty light arrow. 7 grains per pound would be a much better choice for most people.
[quote]


Straightarrow...I was think the same thing you just posted above, glad you clarified that for him. Maybe he either said/typed it wrong or he has the numbers mixed up.

7 grains per inch is very light if he is trying to get KE up.

6.5 to 7 grains per pound of draw weight is dead on in my opinion. I'm thinking he needs to find an arrow around 8.9 to 9.5 grains per inch of arrow lengthto get that weight, not 7 grains per inch of arrow length.

There is alot of new stuff and formulas for any bow hunter to remember, just want to make this crystal clear for him and others reading this post.

Paul L Mohr

The KE will almost always be the same within a few lbs because your bow will only put out so much energy. However the momentum will always increase with heavier arrow and this can help with penitration and down range energy. If I shoot two arrows at a target 20 yards away, one being a fast light arrow and the other being a slow heavy arrow (300 grn/400+ grn) the heavy arrow will hit the target much harder. You can see and hear the difference at the shot.


There is a reason why traditional archers shoot heavier arrows, they just work better out of lower power set ups.

Paul

Arthur P

Remember, once you release the arrow, it begins losing speed, energy and momentum immediately and continues losing it as it cuts through the wind resistance, heading downrange. Since we're talking about crunching numbers, I plugged your numbers into the ballistics calculator over at www.bowjackson.com and here's what I came up with, at 10 yard increments.

Speed, KE and momentum (in pound/seconds)figures for your 314 gn arrow at 269 fps:

0 - 269 50 .3745

10 - 264 49 .3676

20 - 259 47 .3611

30 - 255 45 .3543

So, over 30 yards your 314 gn arrow loses 14 fps in speed, 5 ft lbs ofKEand .0202 pound/seconds of momentum. In percentages, 5.2% loss of speed, 10% in energy and 5.4% in momentum

For your 398 gn arrow:

0 - 244 53 .4306

10 - 241 51 .4244

20 - 237 50 .4186

30 - 234 48 .4126

That arrow lost 10 fps, 5 ft lbs and .0180 pound/seconds in momentum. Or 4% in speed, 9.4% in energy and 4.2% in momentum.

The heavier arrow retained it's speed, energy and momentum better than the light one, which means it retained more penetration potential. Even more important though, the heavy arrow still carried as much KE at 20 yards as your light arrow had at the bow!

At 30 yards,the 398 gn arrowhas only2 ft lbs less energy than the light arrow started out with, and also had more significantly moremomentum than the light arrow had at the bow.

Now, those losses come solely from the arrows cutting though thin air. If the light arrow can't penetrate AIRas well as the heavier one, wouldn't it stand to reason it also can't penetrate a deer's chest cavity as well?

Since increasing your total KE is not going to happen without going to a different bow or increasing your draw weight dramatically, I think the best thing to do is to optimize what KE you ARE getting by using the heavier arrow.

If the decision is between getting the arrow to the deer a few microseconds sooner or increasing the arrow's penetration potential, I know which I'd choose. And I'd alsoecho the suggestions aboutaiming to keep the arrow a little further away from the bones in the shoulder.

arkansasbowhunter

man now that is some number crunching and interesting information. what I was trying to do was use a heavier arrow and still be able to use one pin out to 30 yards. I did increase my arrow weight but I compromised to b/t the 314 and 398 grains I originally started with and settled on the 349 grain arrow by adding 4 inch vanes and the crest. Perhaps, before next year I could increase my draw wt with practice which would enable me to increase my ke. I definetely cannot increase my draw length unless I get put in one of those archaic stretch torture machines

MilDotMaster

Arthur,

Nice job. I was wondering when you were going to pop in and say something. I knew you were a heavy arrow fan. Your info listed above is what I do for myself with a chrono, but have not taken the time to do it for somebody else. Very nice of you to spend the time to helpall of usout with your response. Glad to see somebody else out there likes crunching numbers also.

gibblet

art kicks some serious a%*

Straightarrow

Actually, I'm also a fan of heavy arrows. However, with the above senerio, he has a given arrow that has certain flight characteristics. He's somewhat limited as to what he can do, without weakening the spine too far. As long as he's going to use those light weight arrows, he should still tune them for the best flight, nothing else. Now, when it comes time to buy a new dozen, get some hunting weight arrows, stiff enough to put a nice heavy broadhead on and then he'll notice a real difference in penetration, without screwing up their flight.