We're often asked by customers who are aging or dealing with an ailment such as rotator cuff injuries/surgery and when going to a 50lb bow, what changes do they need to make such as in broadhead, arrows, shot placements, etc.
I'm going to follow up more on this later, but consider the information below.
1985 speed bows
A fast shooting bow at 70lbs and a 28" draw using an 325 grain aluminum arrow with a usually heavier than today 125 grain field point would shoot approximately 235 fps. Total arrow weight is 450 grains and arrow velocity is 235 fps, meaning your kinetic energy would be 55.20 ft-lbs.
Today's compound (2014)
A compound today shooting at 50lbs and a 28" draw using a 280 grain carbon arrow with a 100 grain field point is approximately shooting 255 fps. Total arrow weight is 380 grains and arrow velocity is 255 fps, meaning your kinetic energy would be 54.81 ft-lbs.
Shooting a fairly heavy arrow including field point of 500 grains and a very respectable speed of 165 fps, kinetic energy of a powerful long bow or recurve would be 30.23 fp-lbs.
Big game all through out the world have not only been successfully taken with all three of the bows mentioned above, but extremely clean and efficiently. In terms of kinetic energy, a 50lb bow of today will out perform a compound bow 20 years ago and easily surpass any traditional bow. Add in the fact that the diameter of a carbon arrow is much smaller than a 1985 aluminum arrow or traditional cedar arrow and you then gain that much more penetration. In 1985 with a 70lb bow there would be no question about penetration on elk, bear, bison, moose or any other big game and so using a 50lb bow of today, once again it shouldn't be a question.
Shot placement is always key and still the best in penetration is a sharp cut on contact broadhead; preferably with that 2 to 1 ratio that worked so well many years ago for the great Fred Bear. Dr. Ed Ashby studied arrow performance and broadhead testing for nearly 30 years and I strongly recommend reading his results. If your looking for the best penetration, get a sharp cut on contact 2 to 1 ratio (why we sell the razor sharp Magnus broadheads, USA made and Lifetime warranty - yes send back for replacements) and an arrow set up with 18% or more front of center. Most hunters today using carbon arrows and 100 grain broadheads are only at 9-11% FOC. (note it's been a long while since I read his testing articles but I believe it was 18% to 25% FOC had the best results, anything over 25% made no difference)
Dr. Ashby's broadhead testing articles can be read here among other websites:
Bow set up questions, bow mechanics, archery related info, etc.
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