Brady
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If you want a real scientific discussion of this and other subjects in the
design of firearms I would suggest that you get a copy of:
BRASSEY'S ESSENTIAL GUIDE TO MILITARY SMALL ARMS
Design Principles and Operating Methods
D. Allsop & L.Popelinsky
ISBN 1-85753-107-8
This book is expensive and is one of the most complete discussion of the physics
of firearms. It costs $85.00 per copy.
Eugene N. Neigoff P.E.
..
Fmintz wrote:
> ...
No. The speed of the ejected round also varies with the ammo being used
for semi-automatic weapons, and most likely also with the temperature of
the round when it was fired, the temperature of the round will vary with
the outside temperature and also how long it's chambered in a barrel hot
from previous firings. Some semi-automatic weapons also have a manual
adjustment to allow for variances in the ammo, this adjustment will also
change the ejection speed. For manualy operated guns the speed of
ejection is determined by how fast the shooter moves the bolt.
Forensic technicians may be interested in the range and direction of how
far a shell may or may not travel for a given set of circumstances which
they probably would establish by testing under specific conditions.
Competitive shooters may be interested in getting the shells to land in
a consistent manner for purposes of collecting them, and maybe psyching
others out.
Not blowing up the gun - internal ballistics
Where to aim down range - external ballistics
What happens to incapacitate, damage, or kill - terminal ballistis
Are areas of importance for which information may be found on the web
via search engines. Such information can also be found in a library.
--
Dave Bostock dea...@dc.seflin.org Florida, USA
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1)For a semi automatic case fired 5 feet form the floor, the time to
reach the floor is
t= square root (distance / acceeration )= root (5'/32'/sec/sec)= .4
seconds
2)In a Colt .45 the ejector contacts the case when the slide is back
1.3". The farthest the slide can travel is 1.8" where it hits a stop. If
the spring is perfectly sized for the gun and the round, then the slide
will just run out of energy at the stop. Assume Vslide = 0 at 1.8".
3)Energy Slide at 1.3 inches = (force) (distance)= (16lb
spring)(1.8-1.3=.5")=8 foot pounds of kinetic energy left in slide when
it hits the case
4)Energy is also = 1/2 mass velocity squared = .5 (mass of slide= weight
of slide/ grav accel=12 oz/32 ft/sec/sec)(V squared)
5) Combining equations 3) and 4): Vslide at 1.3" = square
root(E/(.5mass)) = root(8 ft lb/((.5)(.023 lb sec sec /ft)) = 26
feet/sec
6)Center of gravity is .25" from extractor claw and ejector hits the
case at .35" from the extractor claw.
Velocity of case = (.25"/.35")velocity of slide at 1.3" = (.25/.35)26
feet/sec = 18.7 feet per sec [here's your answer] = 12.75 miles per hour
7)Combining 1) and 6): Distance case travels=
(Velocity)(time)=(18.7ft/sec)(.4 sec)=7.46 feet horizontally from the
gun
Also see FAQ at Wolff springs recomends sizing spring to have shells
land at from 3 to 6 feet
http://www.gunsprings.com/
Clark
Fmintz wrote:
> ...
Fmintz wrote:
> ...
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PGP Key http://www.users.fast.net/~tkunz/pgp.html
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Clark Magnuson wrote:
> ...
Good Luck,
Doug T
Gas action, weight of bolt, weight of case don't seem nessecary to me.
5) Combining equations 3) and 4): Vslide at 1.3" = square
root(E/(.5mass)) = root(.66 ft lb/((.5)(.023 lb sec sec /ft)) = 7.6
feet/sec
6)Center of gravity is .25" from extractor claw and ejector hits the
case at .35" from the extractor claw.
Velocity of case = (.25"/.35")velocity of slide at 1.3" = (.25/.35)7.6
feet/sec = 5.4 feet per sec [here's your answer] = 3.6 miles per hour
7)Combining 1) and 6): Distance case travels=
(Velocity)(time)=(5.4ft/sec)(.4 sec)=2.2 feet horizontally from the
gun
Clark
Eric Benson wrote:
#
# > 3)Energy Slide at 1.3 inches = (force) (distance)= (16lb
# > spring)(1.8-1.3=.5")=8 foot pounds of kinetic energy left in slide when
# > it hits the case
#
# Shouldn't that be 8 in-lb?
#
# -Eric
Figuring out the formula to predict the speed of ejection combining bullet weight,
spring strength, barrel length, weight of slide, power, powder charge, mass of the
brass, muzzle velocity, temperature, humidity, posibly even the weight and stregth
of the person holding the pistol might be involved.
MROBINHOOD wrote:
> ...
2) In a Colt .45 the ejector contacts the case when the slide is back
1.3". The farthest the slide can travel is 1.8" where it hits a stop. If
the spring is perfectly sized for the gun and the round, then the slide
will just run out of energy at the stop. Assume Vslide = 0 at 1.8".
3) Energy Slide at 1.3 inches = (force) (distance)= (16lb
spring)(1.8-1.3=.5")=.66 foot pounds of kinetic energy left in slide
when it hits the case
4) Energy is also = 1/2 mass velocity squared = .5 (mass of slide=
weight
of slide/ grav accel=12 oz/32 ft/sec/sec)(V squared)
5) Combining equations 3) and 4): Vslide at 1.3" = square
root(E/(.5mass)) = root(.66 ft lb/((.5)(.023 lb sec sec /ft)) = 7.6
feet/sec
6)Center of gravity [this should be moment of inertia, but that would be
work] is .25" from extractor claw and ejector hits the
case at .35" from the extractor claw.
Velocity of case = (.25"/.35") velocity of slide at 1.3" = (.25/.35)7.6
feet/sec = 5.4 feet per sec [here's your answer] = 3.6 miles per hour
7) Combining 1) and 6): Distance case travels=
(Velocity)(time)=(5.4ft/sec)(.54 sec)=2.9 feet horizontally from the
gun
And Wolff FAQ wants your empties to land from 3 to 6 feet. They must
want the slide to barely hit the stop.
http://www.gunsprings.com/1ndex.html
Clark
-> 1) For a semi-automatic case fired 5 feet form the floor, the time to
-> reach the floor is
-> t= square root ((2)distance / acceleration )= root (5'/32'/sec/sec)= .54
-> seconds
Ejected brass has a vertical component as well as a horizontal
component. This sort of makes the rest of your calculations moot.
I've had brass land anywhere from at my feet to nearly 20 feet away.
The brass tends to keep moving after hiting the ground, even in
grass.
It seems the best thing to do would be to actually measure the
velocity. As someone pointed out, a chrony won't work. However, a
camera will. Get a sound activated shutter control and set up the
camera and the microphone so that the picture will be snaped at a
known time after the shot is fired. The distance the brass has moved
from the pistol can be measured from the image. That should give a
fairly good measure.
--
David Steuber | Hi! My name is David Steuber, and I am
SAJ7580C2 | a hoploholic.
"O, reason not the need!"
-- King Lear
When a fly lands on the ceiling, does it do a half roll or a half
loop?
David Steuber wrote:
#
# It seems the best thing to do would be to actually measure the
# velocity. As someone pointed out, a chrony won't work. However, a
# camera will. Get a sound activated shutter control and set up the
# camera and the microphone so that the picture will be snaped at a
# known time after the shot is fired. The distance the brass has moved
# from the pistol can be measured from the image. That should give a
# fairly good measure.
--
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--
Dave Bostock dea...@dc.seflin.org Florida, USA
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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#Clark Magnuson <cmag...@home.com> writes:
#
#-> 1) For a semi-automatic case fired 5 feet form the floor, the time to
#-> reach the floor is
#-> t= square root ((2)distance / acceleration )= root (5'/32'/sec/sec)= .54
#-> seconds
#
#Ejected brass has a vertical component as well as a horizontal
#component. This sort of makes the rest of your calculations moot.
#
#I've had brass land anywhere from at my feet to nearly 20 feet away.
#The brass tends to keep moving after hiting the ground, even in
#grass.
#
#It seems the best thing to do would be to actually measure the
#velocity. As someone pointed out, a chrony won't work. However, a
#camera will. Get a sound activated shutter control and set up the
#camera and the microphone so that the picture will be snaped at a
#known time after the shot is fired. The distance the brass has moved
#from the pistol can be measured from the image. That should give a
#fairly good measure.
#
Or better yet, have a flash set up to fire several times at known
intervals while the shutter is open. The distance the casing moves
between successive flashes will allow one to calculate both the
speed and the accelleration.
Doug T
P.S. Is to original poster still looking for an answer?