Why brass bullets for 1000yd .50 cal target shooting?

[et...@whidbey.com]

I have a customer who target shoots .50 cal BMG.
He holds world records at 1000 yards. The bullets he shoots are brass.
In fact, I have machined bullets for him, but this was a few years
ago. Why are brass bullets better for this type of shooting? From what
I gather brass is a common material for bullets used for .50 cal BMG
long range target shooting. It seems to me that a more massive bullet
would be less influenced by wind, which must be a major factor when
shooting so far out. I was thinking that a tungsten cored brass bullet
might be better but if it was I'm sure I would have been asked to make
some. The exact size and roundness requirements for the brass bullets
I machined would be very hard to replicate using lead so I can see why
a material that is easy to machine would be desirable. But considering
what folks spend on this sport if there was an advantage to using, for
example, tungsten cored bullets, I think I would have been asked to
make some. Anyway, I'm just curious. The kind of accuracy achieved by
even the mediocre shooters in this sport sorta floors me.
Eric


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[Louis Boyd]

et...@whidbey.com wrote:
# I have a customer who target shoots .50 cal BMG.
# He holds world records at 1000 yards. The bullets he shoots are brass.
# In fact, I have machined bullets for him, but this was a few years
# ago. Why are brass bullets better for this type of shooting? From what
# I gather brass is a common material for bullets used for .50 cal BMG
# long range target shooting. It seems to me that a more massive bullet
# would be less influenced by wind, which must be a major factor when
# shooting so far out. I was thinking that a tungsten cored brass bullet
# might be better but if it was I'm sure I would have been asked to make
# some. The exact size and roundness requirements for the brass bullets
# I machined would be very hard to replicate using lead so I can see why
# a material that is easy to machine would be desirable. But considering
# what folks spend on this sport if there was an advantage to using, for
# example, tungsten cored bullets, I think I would have been asked to
# make some. Anyway, I'm just curious. The kind of accuracy achieved by
# even the mediocre shooters in this sport sorta floors me.

You are wrong that more massive bullets have less wind deflection. The
equation which determines the magnitude of wind deflection is:
D = V * (Ta -Tv)

Where:
D is the linear deflection of the bullet in some units.
V is the wind velocity in the same units as D per second. The vector
direction of D and V are the same and perpendicular to the trajectory.
Ta is the actual time of flight in seconds. Ta can also be expressed as
distance to the target)/(average bullet velocity)

Tv is what the bullets time of flight would be if fired over the same
path in a vacuum (no air drag). Tv can also be expressed as (distance to
the target)/(muzzle velocity).

In all cases the units of time and distance must be in the same units,
(like meters or feet), and all units of time must be the same.

This equation (published in 1859 by Didion) is sometimes called the
"Lag function" because the amount the bullet is deflected is the It is
roughly true for all symmetrical projectiles, whether powered during
their flight or not. There are some minor deviations from this equation
such as spin drift for spin stabilize projectiles and inertial dampening
for fin stabilized projectiles. This equation is embedded in every
commercial ballistics program which calculates wind deflection.
Typically just one line of source code.
At first glance this equation should make it very easy to estimate wind
deflection. It would be if you had an easy way to >measure< time of
flight. It takes a typical complete ballistics program with the G
functions and ballistics programs however to calculate the actual time
of flight.

So why are brass bullets desirable. Look at Didion's equation.
If two bullets have equal muzzle velocity the one with the higher
ballistic coefficient will have the least drag giving it the least wind
deflection. A brass bullet allows making the bullet more streamlined
for the same mass. Bullets of equal mass can be shot to approximately
the same velocity. Making a bullet of tungsten without also changing
it's shape will result in a higher BC but lower velocity.
Some ammo the the military SLAP (saboted light armor piercing) does use
tungsten to achieve both higher velocity and lower BC with sub-diameter
very aerodynamic tungsten bullets. Unfortunately because of the
discarding sabot it's not very accurate. The 50 BMG simply isn't enough
cartridge to drive a long full diameter projectile to the needed
velocity. The 30mm cannon on Warthogs and the 150mm main gun on the
Abrams tank does achieve the needed velocity and the latter has
amazingly low wind deflection.

Brass (certain alloys of copper, tin, and ?) has other good properties.
Machines easily. (compared to tungsten)
Homogeneous (few voids in brass stock)
engraves well in rifle barrels (compared to tungsten)
Relatively inexpensive (compared to tungsten)
There are some use for a tungsten/lead amalgam (mostly tungsten) for
shot which can be used for bullet cores, but it offers little in
ballistic performance.

I shoot brass bullets (800 grain Barnes bore riders) in my 50 BMG bench
rifle. Those bullets are too long to fit in typical 50 BMG semi-autos
or machine guns. Also the longer bullets may need a faster twist
barrel to stabilize. The required twist isn't only a function of the
bullet (length, shape and weight) but also of the muzzle velocity, and
the air density. Lehigh also sell high BC specialty brass bullets for
the 50 BMG.

[Martin Eastburn]

I would think bronze would be better for a flight but tougher
on the barrel. Si-Bronze. Gold in color. Tough almost like A36 or better.

Martin

[David Griffith]

et...@whidbey.com wrote:
# I have a customer who target shoots .50 cal BMG.
# He holds world records at 1000 yards. The bullets he shoots are brass.
# In fact, I have machined bullets for him, but this was a few years
# ago. Why are brass bullets better for this type of shooting? From what
# I gather brass is a common material for bullets used for .50 cal BMG
# long range target shooting. It seems to me that a more massive bullet
# would be less influenced by wind, which must be a major factor when
# shooting so far out. I was thinking that a tungsten cored brass bullet
# might be better but if it was I'm sure I would have been asked to make
# some. The exact size and roundness requirements for the brass bullets
# I machined would be very hard to replicate using lead so I can see why
# a material that is easy to machine would be desirable. But considering
# what folks spend on this sport if there was an advantage to using, for
# example, tungsten cored bullets, I think I would have been asked to
# make some. Anyway, I'm just curious. The kind of accuracy achieved by
# even the mediocre shooters in this sport sorta floors me.

Why don't you talk to some of these shooters and see if they'd be
interested in running some tests of cored bullets versus solid brass
bullets? I'm sure at least readers of this newsgroup will find the
results interesting.


--
David Griffith

[Larry Fishel]

On Friday, November 16, 2012 8:56:36 AM UTC-5, et...@whidbey.com wrote:
# But considering
# what folks spend on this sport if there was an advantage to using, for
# example, tungsten cored bullets, I think I would have been asked to
# make some.

How would you ensure that the core was centered in the bullet down to the kind of accuracy that you are machining to?

[et...@whidbey.com]

Thanks for the post Louis,
So it looks like, from the formula given, that mass is not taken into
account at all regarding wind deflection? This would mean that two
bullets with the same exact shape travelling at the same speed would
be deflected by the same amount no matter what the mass? I was taught
that the more massive an object is the more inertia it has and hence
the harder it is to move from the path it is taking.
Eric

[et...@whidbey.com]

I would probably bore a collet that fits the bullet and bore the
bullet to accept the heavy insert. I may need to hold the collet in an
adjustable nose piece to make sure any runout can be adjusted out.
Making them in high numbers would require me to buy a Northfield
diaphragm air chuck or something similar.
Eric

[et...@whidbey.com]

I did talk to my customer about this. He was trying other things at
the time, bullet shapes and diameters for example, and didn't want to
add yet another variable. I still do work for him but no longer make
bullets.
Eric

[Joe Pfeiffer]

# Tv is what the bullets time of flight would be if fired over the same

# path in a vacuum (no air drag). Tv can also be expressed as (distance to
# the target)/(muzzle velocity).

Ta-Tv depends on the mass of the bullet (and a bunch of other factors).
All else being equal a lighter bullet will have more deceleration due to
air resisteance, so Ta-Tv will be greater.

<snip>

# So why are brass bullets desirable. Look at Didion's equation.
# If two bullets have equal muzzle velocity the one with the higher
# ballistic coefficient will have the least drag giving it the least wind
# deflection. A brass bullet allows making the bullet more streamlined
# for the same mass. Bullets of equal mass can be shot to approximately
# the same velocity. Making a bullet of tungsten without also changing
# it's shape will result in a higher BC but lower velocity.

Right -- same mass with different ballistic coefficient, or same BC with
more mass...

[Martin Eastburn]

Brass = copper & Zinc in some combination. Normally soft.
Bronze = copper & Tin in some combination. Normally hard.

Si Bronze - add silicon to the Bronze. A hard tool grade Bronze.

I would think if it were zinc copper - a brass - it would be to soft
for hard surface work.

Tungsten core would make it armor piercing. Where the bolt of Tungsten
vaporizes the target as the carrier metal flows and sheds.

Martin

[Bob Holtzman]

On 2012-11-18, et...@whidbey.com <et...@whidbey.com> wrote:
# Thanks for the post Louis,
# So it looks like, from the formula given, that mass is not taken into
# account at all regarding wind deflection? This would mean that two
# bullets with the same exact shape travelling at the same speed would
# be deflected by the same amount no matter what the mass? I was taught
# that the more massive an object is the more inertia it has and hence
# the harder it is to move from the path it is taking.

Mass is taken into account indirectly in that the more massive
projectile (all things being equal...which they never are) should shed
velocity slower than a less massive one, thus less lag.

--
Bob Holtzman

[Gunner]

On Sun, 18 Nov 2012 01:20:23 +0000 (UTC), et...@whidbey.com wrote:

#I would probably bore a collet that fits the bullet and bore the
#bullet to accept the heavy insert. I may need to hold the collet in an
#adjustable nose piece to make sure any runout can be adjusted out.
#Making them in high numbers would require me to buy a Northfield
#diaphragm air chuck or something similar.
#Eric

Or a decent screw machine such as an Acme Gridley or similar. They can
be had for peanuts these days.

Or I can sell you a nice new or used OmniTurn

www.omniturn.com
www.omni-turn.com

A number of 50 cal bullet prototypes have been done on them with very
good sucess.

Gunner

[et...@whidbey.com]

On Sun, 18 Nov 2012 13:14:01 +0000 (UTC), Bob Holtzman
<hol...@cox.net> wrote:

#On 2012-11-18, et...@whidbey.com <et...@whidbey.com> wrote:
## Thanks for the post Louis,
## So it looks like, from the formula given, that mass is not taken into
## account at all regarding wind deflection? This would mean that two
## bullets with the same exact shape travelling at the same speed would
## be deflected by the same amount no matter what the mass? I was taught
## that the more massive an object is the more inertia it has and hence
## the harder it is to move from the path it is taking.
#
#Mass is taken into account indirectly in that the more massive
#projectile (all things being equal...which they never are) should shed
#velocity slower than a less massive one, thus less lag.
Greetings Bob,
Your statement above makes perfect sense.
Thanks,
Eric

[Larry Fishel]

On Saturday, November 17, 2012 8:20:23 PM UTC-5, et...@whidbey.com wrote:
# I would probably bore a collet that fits the bullet and bore the
# bullet to accept the heavy insert. I may need to hold the collet in an
# adjustable nose piece to make sure any runout can be adjusted out.
# Making them in high numbers would require me to buy a Northfield
# diaphragm air chuck or something similar.

Duh. We were talking bullets, so my brain skipped over that fact that we were using metals that could be machined...

[benevenu...@yahoo.com]

On Saturday, November 17, 2012 6:38:15 AM UTC-6, Louis Boyd wrote:
"...

You are wrong that more massive bullets have less wind deflection.

..."

Nonsense. If all other factors are the same a heavier bullet will be deflec
ted less by the wind.

Make one bullet of plastic and a second of lead. Both have the same dimensi
ons. The lead bullet will be deflected less by the wind. Why?

Because the force applied by the cross-wind to both bullets is identical, b
ut the consequent acceleration of the lead bullet is less (F=3Dma and a=3DF
/m and m is larger for the lead bullet). Thus it requires more time for the
cross-wind to accelerate the lead bullet to equal the cross-wind speed.

Similarly toss a lead ball straight up in the air during a cross-wind and t
hen a styrofoam ball of the same dimensions. The styrofoam ball will be def
lected more.

Furthermore, since the time of flight of the bullet is low, the lead bullet
usually never accelerates to the cross-wind's speed (unless you're taking
a really long shot).

[Ralph Mowery]

Here is where you can run the calculations yourself.
http://handloads.com/calc/

As you can not drive a heavy bullet as fast as a lighter bullet in the same
gun, the faster bullet will deflect less at 1000 yards. Time to target is
often the most important thing at the longer ranges.

Try it with the numbers of a typical 30/06. Use 3000 fps for a 150 gr
bullet and 2700 fps (which is too much) for a 220 gr bullet. The 150 gr
will deflect less.

Be sure to use the BC calculator on the left side for each bullet.

[Bob Holtzman]

On 2012-11-19, Ralph Mowery <rmower...@earthlink.net> wrote:
#
# Here is where you can run the calculations yourself.
# http://handloads.com/calc/
#
# As you can not drive a heavy bullet as fast as a lighter bullet in the same
# gun, the faster bullet will deflect less at 1000 yards. Time to target is
# often the most important thing at the longer ranges.

Not time to target but lag time is the important factor.

--
Bob Holtzman

[benevenu...@yahoo.com]

On Monday, November 19, 2012 1:28:09 PM UTC-6, Ralph Mowery wrote:
# Here is where you can run the calculations yourself.
# http://handloads.com/calc/
...

If simple physics defies you then there is no reason for me to run a ballis
tics program. The program may work properly and give the right answers give
n it's assumptions. However what I am saying is true regardless of the ball
istics program.

It is basic physics that, if all dimensions and initial conditions are iden
tical, then a heavier (therefore more dense) bullet (or ball or block or wh
atever) will be deflected less than a lighter(therefore less dense) bullet
(or ball or block or whatever).=20

Let me try again to phrase my use of Newton's law (since Google Groups is m
essing up my equal sign and appending the characters "3D" for some reason):
=20

The force applied by the cross-wind to both bullets is identical,=20
but the consequent acceleration of the lead bullet is less: force F is equa
l=20
to mass * acceleration and therefore acceleration is force / mass and the
=20
mass is greater for the lead bullet, making it's acceleration less. Thus it
=20
requires more time for a cross-wind to accelerate the lead bullet to the p
oint where it's transverse speed equals the cross-wind speed. In fact it is
=20
unlikely that the bullet's transverse speed _ever_ reaches the cross-wind s
peed.

[Ralph Mowery]

Maybe you are missing the point that in the same gun a lighter bullet can
safely be driven to a higher velocity than the heavy one.

Using a 30 caliber Serria 190 and 200 matchking bullets the 190 gr bullet
can be driven 100 fps faster than the 200 gr bullet. Given the 100 fps
differance the 190 gr bullet will have less wind drift than the 200 gr
bullet.

If you did not miss that the lighter bullet is going faster, it would be
pointless for anyone to try to enlighten someone that knows more than the
people at Serria.

[SaPeIsMa]

The fact that is ignored in the above thread is that if you apply the same
amount of force over different time spans, there will be a point where the
cumulative effect on the heavier/slower bullet will be greater deflection
than on the lighter/faster bullet.

[Larry]

In article <k85gmj$hkc$1...@news.albasani.net>, et...@whidbey.com says...

# I have a customer who target shoots .50 cal BMG.
# He holds world records at 1000 yards. The bullets he shoots are brass.
# In fact, I have machined bullets for him, but this was a few years
# ago. Why are brass bullets better for this type of shooting?

It depends on how the bullets engage the rifling. I don't know the details,
but know that some .50 BMG match rifles will not shoot conventional ammo.

[et...@whidbey.com]

On Tue, 20 Nov 2012 02:50:59 +0000 (UTC), "SaPeIsMa"
<SaPe...@Hotmail.com> wrote:

#
#The fact that is ignored in the above thread is that if you apply the same
#amount of force over different time spans, there will be a point where the
#cumulative effect on the heavier/slower bullet will be greater deflection
#than on the lighter/faster bullet.
#
This is something I didn't consider, that a heavier bullet would be
going slower for the same amount of push from the rifle. But if a
marksman did decide that a heavier bullet would be better then he
would compensate by using more propellent. That is if the rifle could
handle the extra energy. I imagine the real reasons for using brass
bullets are many and they all converge on a small range of material
densities.
Eric

[Bob Holtzman]

On 2012-11-20, Ralph Mowery <rmower...@earthlink.net> wrote:
#

# Maybe you are missing the point that in the same gun a lighter bullet can
# safely be driven to a higher velocity than the heavy one.

And you may have missed the fact that he was basing his conclusion on the
assumption of all things being equal which,of course, they never are.
This means that while he's right from a theoretical perspective, you're
right in the real world.

.........snip........

--
Bob Holtzman

[Larry Fishel]

On Monday, November 19, 2012 9:50:57 PM UTC-5, Ralph Mowery wrote:
# Maybe you are missing the point that in the same gun a lighter bullet can
# safely be driven to a higher velocity than the heavy one.
#
#
#
# Using a 30 caliber Serria 190 and 200 matchking bullets the 190 gr bullet
# can be driven 100 fps faster than the 200 gr bullet. Given the 100 fps
# differance the 190 gr bullet will have less wind drift than the 200 gr
# bullet.

However, the topic of discussion is 1000 yard target shooting. By 1000 yards, the 200gr bullet has caught up due to it's higher BC.

In both scenarios you laid out, using the calculator you posted a link to, I get less wind drift with the heavier bullet. In the first case (220 vs 150) I get almost twice the drift at 1000 yards for the lighter bullet. Am I missing something?

[Larry Fishel]

On Tuesday, November 20, 2012 5:22:05 PM UTC-5, et...@whidbey.com wrote:
# But if a
# marksman did decide that a heavier bullet would be better then he
# would compensate by using more propellent.

We all with that were true, but here is the key...

# That is if the rifle could
# handle the extra energy.

In the read world, guns used for long range target shooting are limited by
peak pressure that can be safely handled in the chamber (the brass is often
(intentionally) the weakest link). Since the lighter bullets are already c
reating near maximum safe pressure and heavier bullets remain in the barrel
longer (pressure is increasing over time) you actually have to use LESS po
wder with a heavier bullet... (In certain cases you can switch to different
powder and make up some of the difference.)

[Larry]

In article <k8h8d9$h4l$1...@news.albasani.net>, ldfi...@yahoo.com says...
# In the read world, guns used for long range target shooting are limited by
# peak pressure that can be safely handled in the chamber (the brass is often
# (intentionally) the weakest link). Since the lighter bullets are already c
# reating near maximum safe pressure and heavier bullets remain in the barrel
# longer (pressure is increasing over time) you actually have to use LESS po
# wder with a heavier bullet... (In certain cases you can switch to different
# powder and make up some of the difference.)

Very sophisticated engineers at Federal have learned how to use a mix of
powders to achieve higher velocities while still staying within SAAMI limits.
The Federal Premium .30-06 load is a good example.

[et...@whidbey.com]

After I made my last post I thought about the longer travel time of a
heavier bullet and wondered what that might do because of the way the
powder burns. The rifles I've seen have 1.5" diameter barrels. There
must be a reason for that besides making them hard to carry around.
Eric

[Larry]

In article <k8j38q$sms$1...@news.albasani.net>, et...@whidbey.com says...
#
# After I made my last post I thought about the longer travel time of a
# heavier bullet and wondered what that might do because of the way the
# powder burns. The rifles I've seen have 1.5" diameter barrels. There
# must be a reason for that besides making them hard to carry around.

Less barrel whip with a stiffer spring. Also more thermal mass, so they don't
change that much from shot to shot. The old time exhibition shooters used to
dunk their guns in barrels of water to cool them off.

[Larry Fishel]

On Thursday, November 22, 2012 3:48:01 AM UTC-5, Larry Caldwell wrote:
# Less barrel whip with a stiffer spring. Also more thermal mass, so they don't
# change that much from shot to shot. The old time exhibition shooters used to
# dunk their guns in barrels of water to cool them off.

Also, more total mass of the gun means more tolerable recoil. Not insignificant in a .50.