To elaborate further...

Why give up trajectory to gain a trivial amount of momentum when your setup is already packing that much energy?

What #draw are you using with your BOWTECH? I have 4 friends that all shoot bowtech and non of them with 400 gr arrow are hitting 300 fps.

I shoot a mathews. 550gr arrow[2514 xx78, 125 gr point]. at 29 in draw set to 90# and I do not get 300 fps.I am sure when I turn it up to 100# I will be in the 310 to 320 fps range.

I think there is a ton of people that kinda push what they get for FPS.

To get 300fps at 400 grains my specs are 29 inch DL and 70.5#.

I would hope you are not trying to include me in there.

Here is a pic of my BC....... Oh yea she smokes

The further down range you get the heavier arrows will have more KE, they don't loose speed as fast as the lighter arrows. At most eastern US ranges this is probably insignifcant, as in the trajectory loss for most shots around here if you know your bow and your hunting spot but once you go out west and see people launching arrows at 40-60 yards the numbers will start looking a little different. The trajectory will get you with the heavier arrows but the KE will be in their favor out that far. This is one place where momentum does matter. Pick your poison on this one.

I personally like a slightly heavier arrow because it is a little quieter, a little less stress on the bow as more energy is absorbed by a heavier arrow, and in my bows case it is more effiecient to use heavier arrows. I'm not talking 600 grain fence posts, I'm talking 450-500 grain out of a 65 pound bow. Or 450 out of my 55 pound bow.

Trapper--a 'slightly' over-spined heavier arrow will give you more consistency in KE further down range than will a lighter arrow.
Me, I prefer a slightly over-spined heavier arrow, helps silence the bow, will maintain its speed and will pack a punch.

A summary of the factors that determine initial Kinetic Energy...

There are exactly no more and no less than 2 factors that determine the amount of initial KE. They are: 1) The amount of biochemical energy the archer is able to transfer to mechanical energy stored in the bow limbs. This is bascially a fucntion of how strong the archer is but it is also influenced to a lesser degree by the ergonomic design of the bow. 2) The amount of stored mechanical energy the bow transfers to the arrow on release which is called efficiency. The higher the efficiency the more initial KE. Efficiency is effected by 2 factors. 1) The internal resistance the bow has to acceleration which is summed up in a term called virtual mass. Virtual mass is basically frictional resistance called dynamic hysterisis plus the resistance to acceleration due to the need to also accelerate the mass of the moving parts in the bow during launch which of course drains potential KE from the arrow. Virtual mass for a modern bow is typically around 100 grains. If you would like a better explination of virtual mass see http://homepage.ntlworld.com/joetapley/. The second and stonger factor effecting efficiency is arrow mass. The heavier the arrow the more efficient the bow transfers its mechincal energy, the lighter the arrow the less efficient.

To sum up, if you want more initial KE then you must transfer more biochemical energy to the bow, lower the bows virtual mass, or shoot a heavier arrow. There are no other options.

So "what is the best way to get kinetic energy?"

I don't know about best, best is somewhat subjective but think about this. Shooting more weight and shooting heavier arrows both have some downside associated with them. If you increase your weight too much it may negatively effect your ability to shoot accurately. Too heavy an arrow will produce a larger arch in trajectory making it more critical to judge distance accurately. The only factor that is "free" so to speak is to keep virtual mass as low as you can. If you use string silencers, choose the lightest you can that still do the job. If their are lubrication needs for your bow be sure its done regualarly. Use string knocs that are as light as possible. Also if you have things that are vibrating and/or making noise try to eliminate it. Doing this things won't make a huge difference but hey its free KE.

Not true , a heavier arrow will soak up more energy while on the string and carry it with it further than a light arrow .


Increase draw weight , decrease brace height , get all the junk off of your string , and use a heaver arrow . Those are the easy est ways , making sure your bow is tuned , using a narrower string that has the correct amount of twists , or x-coat to prevent ballooning , lubing axles and various others will give less dramatic returns .

edit - longer draw will do it to , but your draw "is what it is" so its not an option .

speed counts more towards KE ........ very fast and light will on paper get you more KE

in the real world momentum is probably a better way to measure penetration

It is misleading to say that speed counts more towards KE. Counts more than what?

The initial kinetic enery an arrow will cary is equal to the energy stored in the limbs of the bow minus the amount of energy wasted in the launch. Heavier arrows shot from the same bow waste less energy in the lauch and consequently cary more initial kinetic energy. Can lighter faster arrows cary more KE than heaview slower arrows. Of course but that doesn't say anything practical. A practical statement is that if you shoot a heavier arrow out of the same bow it will cary more KE than a lighter arrow shot from the same bow.