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Wickes Simon
07-23-2000, 06:39 PM
Enclosed is a summary of responses to the weapons recoil query.

Thank you for your time and effort

Simon Wickes


-----Original Message-----
From: Geoffrey Kotzar [SMTP:gkotzar@biomec.com]

Subject: Re: Weapons recoil


I cannot answer your question based on information from the literature
but can provide some observations from personal experience. It is a more
complicated issue than can be simply expressed in terms of blunt trauma.
It is quite possible to handle weapons safely that recoil in the range
of 85 to100 ft-lbs without injury. However, at the 60 ft-lb range, if
the weapon is not properly shouldered it CAN result in serious injury to
the shooter with even one round. It is necessary to keep the firearm
properly located and not allow it any "running" room or it will bruise
soft tissue structures. Early in my experience with a .458 Winchester, I
fired one round from the standing position that slipped and banged me in
the shoulder. I was unable to even shoulder the gun for over a week,
much less fire it. After I learned how to handle it properly, I was able
to fire 40 or more rounds from a seated position at a bench without
injury and with good accuracy even at the end of the session. And this
was with rounds that were more powerful than the factory loads. By the
time I was able to do this, I had fired hundreds of rounds over the
course of a year or more.
But to first summarize some of the variables involved, free recoil
energy is only one. Second is the free recoil velocity. Those weapons
that recoil at higher velocities will be perceived as recoiling harder.
This, of course, assumes that we are talking about comparable free
recoil energy. Another variable is the number of rounds that the shooter
must fire with what degree of accuracy. Another is the training time
allowed for each individual. In reverse order, most anyone can be
trained to handle these heavy recoiling arms with surprising accuracy
but it takes time, and it can take a lot of it. It is necessary to build
tolerance slowly. The number of rounds that must be fired will strongly
determine what can be tolerated. Competitve shooters have found that the
recoil level of the old U.S. battle rifle cartridge, the .30-06, had
about all the recoil that the average individual could learn to handle
in a reasonable length of time. Furthermore, extend shooting sessions,
as required in many competitions, would result in "shooter headache".
The recoil level of the .30-06 in guns of that era was around 18 ft-lbs
if I remember correctly. As recoil levels increase, the shooter's
tolerance decreases. Aside from a headache, many people will develop a
substantial flinch where they anticipate being hit by the buttstock.
Here I am refering to being hit in the shoulder and the cheek, as well.
This destroys accuracy completely. Therefore, as recoil goes up the
number of accurate rounds that can be delivered must of necessity go
down.
The second variable, free recoil velocity, and its effect can be
illustrated by two two commercial hunting rounds: the .378 and .460
Weatherbys. Both are based on the same case with the same powder
capacity. Therefore the masses of the powder ejecta are equal and their
contributions to the momentum of the total ejected mass are the same.
Bullet weights are 300 grains and 500 grains, respectively. The weight
of the rifles are such that the free recoil energy is greater for the
460, by a substantial margin, but the .378 has a reputation as being a
much less pleasant rifle to shoot. The reason is attributed to the high
muzzle velocity of the .378 (3000 fps) versus 2500 fps for the .460 and
the corresponding short barrel time. Both barrels are the same length,
by the way. In standard weight rifles, the free recoil energies are 65
ft-lbs and 85 ft-lbs for the .378 and .460, respectively.
I don't know if the above can be of any help to the individual who
originally posed the question to you. But my guess is that the proposed
limit of 60 ft-lbs probably is based on something other than blunt
trauma, although the configuration and material of the military
buttstock may make blunt trauma a consideration. Most sporting rifles at
that level of recoil have integral pads for the shoulder.



Geoffrey M. Kotzar, Ph.D.
Program Manager
BIOMEC, Inc.
1771 E. 30th St.
Cleveland, Ohio 44114

216-937-2800 x229 (Ph)
216-937-2812 (FAX)

-----Original Message-----
From: Chuck Pell [SMTP:cap@ntrobotics.com]

Sent: Tuesday, July 18, 2000 8:26 PM
To: Wickes Simon
Subject: Re: Weapons recoil

Try the Piccatinny Army Base Research Library and similar resources.



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