Bow question

[Bigshooter19]

Hello my buddy is shooting a Bowtech destroyer 350. Shooting 70 lbs at 26 in draw shooting 305 fps. Are local archery shop (which i think the guy is a dumb***) has him shot carbon express 250 grain arrow. Also made him switch to 125 grain tips to gain more kinetic energy. I was wondering if anyone had any suggestion on how to gain more energy? I told him to switch to a 400 grain arrow with a 100 grain tip but i don't know. Thanks for the help!

 

[mglenn005]

Kinetic energy = 0.5*mass*velocity*velocity
Or 0.5*m*v^2

That is mass of the arrow. Check the units because they can be confusing but there are bow kinetic energy calculators on the web.

I would shoot the correct spine stiffness arrow and make sure that is proper before anything else. I would also rather have accuracy and silence than speed and noise.

The speed of sound is 1125 feet per second or 375 yards per second.


Consider a 30 yard shot (90ft):
300 fps bow gets the arrow there in 0.3 seconds.
If you shot 275 fps, it's 0.33 seconds. Not much difference and any alert deer will jump the string on both. I'm confident to say that the reaction time of a deer is way less than 0.3 seconds.

Speed is not king. Shoot a quiet bow. Shoot the combination of arrow, fletchings, broad heads that are the quiet and accurate.


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[Bszweda]

Rule of thumb you need atleast 5 grains per pound to be safe. He would need to be at least 350.( I guessing he's already at this weight)This is your typical Ibo setup and with his short draw length those speeds are around right.Are you sure he's not shooting 250 spine arrows? You have the right idea with a heavier arrow. It will quiet the bow down considerably & give you momentum. The only thing is a heavier arrow is less forgiving in yardage mistake. However won't make much of a difference at typical ranges 20 - 30. Definitely make sure his broadheads hit close to his field points. High fps bows, with straight vanes can be a pain to tune. I'd suggest a right helical.

 

[yoderjac]

Kinetic energy = 0.5*mass*velocity*velocity
Or 0.5*m*v^2

That is mass of the arrow. Check the units because they can be confusing but there are bow kinetic energy calculators on the web.

I would shoot the correct spine stiffness arrow and make sure that is proper before anything else. I would also rather have accuracy and silence than speed and noise.

The speed of sound is 1125 feet per second or 375 yards per second.


Consider a 30 yard shot (90ft):
300 fps bow gets the arrow there in 0.3 seconds.
If you shot 275 fps, it's 0.33 seconds. Not much difference and any alert deer will jump the string on both. I'm confident to say that the reaction time of a deer is way less than 0.3 seconds.

Speed is not king. Shoot a quiet bow. Shoot the combination of arrow, fletchings, broad heads that are the quiet and accurate.


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Great response! Just to add a bit, start with the game you are hunting. For whitetail deer with a modern bow and a well placed shot and sharp broadhead, kinetic energy is not a factor. If you are taking long distance shots and spraying arrows and are concerned about hitting a shoulder bone, again, kinetic energy is a non-factor. You can't get enough to penetrate a shoulder and get a good low exit wound with a blood trail that gives you a high probability of recovery.

Reduce shot distance (I restrict myself to about 20 yards) and take only good shot angles. That will get you 90% there.

The second biggest factor is poor distance estimation. Some folks try to shoot a very fast bow to overcome this. As you stated in your response, shooting a quiet bow is more important. Distance estimation error can be compensated for in other ways. An average modern compound will shoot pretty flat out to 20 yards. If you limit your range to that, you remove pin selection mistake as a factor. By using a laser range finder to range trees when you first enter your stand and memorizing the distance you can all be eliminate ranging error at ranges under 25 yards. If you are over a field, a safety flag at 20 yard and possibly 30 yards accomplishes the same thing.

So, back to kinetic energy. Your math is right . Folks should understand that velocity is more important than mass because it is squared in the equation when it comes it kinetic energy when the arrow leaves the bow. However, what you are concerned with is the retained kinetic energy down range when the arrow impacts the deer. Mass in the arrow helps retain the energy down range, but more importantly is the tuning. Having the correct spine given your setup and a well tuned bow reduces the volatility of the arrow faster when it leave the bow. The means less energy is lost to drag in addition to a more accurate arrow.

Just trying to expand on a good answer for others...

Thanks,

Jack

 

[mglenn005]

Another thing to consider and I have no clue who your friend is or his physical ability. But, if you can't hold your bow at full draw for 30 seconds then find your target and not accurate at "insert comfort range, say 30 yds," you might want to drop the draw weight and give up some speed. You also may make a lot of movement drawing back a heavy draw weight which could alter deer.


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[yoderjac]

Another thing to consider and I have no clue who your friend is or his physical ability. But, if you can't hold your bow at full draw for 30 seconds then find your target and not accurate at "insert comfort range, say 30 yds," you might want to drop the draw weight and give up some speed. You also may make a lot of movement drawing back a heavy draw weight which could alter deer.


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Another great response. When I help folks setting poundage, I have them sit in a chair an draw the bow. I then have them lift one foot off the ground and draw again and then switch feed and draw the bow again. This ensures they are drawing with only upper body strength. If they can draw smoothly and comfortably and then let down with sufficient control, the poundage is good for hunting. You can shoot a lot more poundage standing firmly on a range.

Another thing to consider is draw length. I shorten my target or 3D draw length by at lest and inch and maybe a bit more. The reason for this is that most shot opportunities from a treestand will not afford you perfect from. You can maintain form in many more positions in a treestand when your draw length is a bit shorter.

All of these things will result is a slower smoother shooting bow but a much higher percentage of deer harvests and recoveries.

Thanks,

Jack

 

[mglenn005]

Great response! Just to add a bit, start with the game you are hunting. For whitetail deer with a modern bow and a well placed shot and sharp broadhead, kinetic energy is not a factor. If you are taking long distance shots and spraying arrows and are concerned about hitting a shoulder bone, again, kinetic energy is a non-factor. You can't get enough to penetrate a shoulder and get a good low exit wound with a blood trail that gives you a high probability of recovery.

Reduce shot distance (I restrict myself to about 20 yards) and take only good shot angles. That will get you 90% there.

The second biggest factor is poor distance estimation. Some folks try to shoot a very fast bow to overcome this. As you stated in your response, shooting a quiet bow is more important. Distance estimation error can be compensated for in other ways. An average modern compound will shoot pretty flat out to 20 yards. If you limit your range to that, you remove pin selection mistake as a factor. By using a laser range finder to range trees when you first enter your stand and memorizing the distance you can all be eliminate ranging error at ranges under 25 yards. If you are over a field, a safety flag at 20 yard and possibly 30 yards accomplishes the same thing.

So, back to kinetic energy. Your math is right . Folks should understand that velocity is more important than mass because it is squared in the equation when it comes it kinetic energy when the arrow leaves the bow. However, what you are concerned with is the retained kinetic energy down range when the arrow impacts the deer. Mass in the arrow helps retain the energy down range, but more importantly is the tuning. Having the correct spine given your setup and a well tuned bow reduces the volatility of the arrow faster when it leave the bow. The means less energy is lost to drag in addition to a more accurate arrow.

Just trying to expand on a good answer for others...

Thanks,

Jack

Jack, good follow up. On phone here and didnt want to get all engineering and technical.

I range find and know my distances. I practice estimating year round (golf).

I used to shoot a reflex excursion (Hoyt off brand) and I calculated my bow efficieny was as 95% by integrating the draw weight curve and comparing to kinematic energy at 5 ft post release.

For non technical folks... Energy is always conserved. So it either goes to the arrow in velocity, some small friction and heat generation (tiny tiny and almost negligible) or it makes noise through vibration.


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[mglenn005]

Another great response. When I help folks setting poundage, I have them sit in a chair an draw the bow. I then have them lift one foot off the ground and draw again and then switch feed and draw the bow again. This ensures they are drawing with only upper body strength. If they can draw smoothly and comfortably and then let down with sufficient control, the poundage is good for hunting. You can shoot a lot more poundage standing firmly on a range.

Another thing to consider is draw length. I shorten my target or 3D draw length by at lest and inch and maybe a bit more. The reason for this is that most shot opportunities from a treestand will not afford you perfect from. You can maintain form in many more positions in a treestand when your draw length is a bit shorter.

All of these things will result is a slower smoother shooting bow but a much higher percentage of deer harvests and recoveries.

Thanks,

Jack

Good tips as well!


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