22 long rifle wind drift
Ralph Mowery
stated that if you shot a low velocity and a high velocity 22 rimfire the
lower velocity would have less wind drift. They also mentioned the higher
speed center fires had the opposit effect as they were supersonic.
Is it possiable the slower bullet has less wind drift than the faster one at
low velocities.
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mehrdad ghassempoory
I am not a firearms expert, but I know my dynamics and
this does not make sense. Could it be that the lower
speed 22 cartridges have the same amount of charge as
high speed ones but they have heavier bullets? More
mass will give the bullet more inertia, so it would
be harder to divert it from the course. At any rate
I though that high velocity 22 is (just) supersonic.
A look at Remington site info on 22 somehow confirms
my suspicion: 22 Standard velocity/Target is 40 grains
while the hyper velocity ones are at 33 and 36 grains.
Can someone with more experience and knowledge comment
on this?
Ralph Mowery wrote:
> ...
DougC
# Is it possiable the slower bullet has less wind drift than the faster one
Think of it this way: There is a constant wind at 90 degrees across
the path of the bullets. The slower bullet takes longer to get to the
target, so it has a longer push from the crosswind.
Doug Chandler
Jim Yanik
news:h1ub81$m20$1...@news.albasani.net:
# I was looking at an American Hunter magazine and in it was a quiz.
# They stated that if you shot a low velocity and a high velocity 22
# rimfire the lower velocity would have less wind drift. They also
# mentioned the higher speed center fires had the opposit effect as they
# were supersonic.
#
# Is it possiable the slower bullet has less wind drift than the faster
# one at low velocities.
seems to me that the slower bullet would be more affected by wind
drift,having a longer travel time.
--
Jim Yanik
jyanik
at
kua.net
Brian Whatcott
# I was looking at an American Hunter magazine and in it was a quiz. They
# stated that if you shot a low velocity and a high velocity 22 rim fire the
# lower velocity would have less wind drift. They also mentioned the higher
# speed center fires had the opposite effect as they were supersonic.
#
# Is it possible the slower bullet has less wind drift than the faster one at
# low velocities.
1
1
1
Bullets near the speed of sound see more turbulence than both those
that fly slower, and those spending their trajectory at supersonic speed.
Remember the sound-barrier? This is it!
http://www.gunsmoke.com/guns/1022/22drift_cross.html
Brian Whatcott Altus OK
Bob Holtzman
# I was looking at an American Hunter magazine and in it was a quiz. They
# stated that if you shot a low velocity and a high velocity 22 rimfire the
# lower velocity would have less wind drift. They also mentioned the higher
# speed center fires had the opposit effect as they were supersonic.
#
# Is it possiable the slower bullet has less wind drift than the faster one at
# low velocities.
As usual the news stand mags only get their facts half right. A high
speed .22 leaves the barrel at supersonic velocity, greater than 1100
and some odd ft/sec. shortly thereafter the velocity drops into the
trans-sonic range where it becomes unstable and subject to buffeting. At
that point it is much more wind sensitive than a bullet that never gets
up to supersonic velocities, i.e. a standard velocity round, what you
refer to as "low velocity". A centerfire round almost always stay
supersonic all the way to the target and never sees the tran-sonic
range. This is the reason .22 match ammo, with rare exceptions. is always
loaded to subsonic velocity. High power shooters who compete at long
range, i.e. Palma matches and the various 1000 matches, are carefull to
load hot enough to stay supersonic all the way.
--
Bob Holtzman
AF9D 8760 0CFA F95A 6C77 E125 BF90 580F 8D54 9279
"If you think you're getting free lunch,
check the price of the beer"
Rubaiyat of Omar Bradley
faster one at low velocities.>>
Sometimes yes, sometimes no...
Comparing 3 Federal loads, all with 40gr. bullets, we see these wind
drift amounts, in a 10mph wind:
Load "UM22" MV 1080fps drift 1.6" at 50 yards, 5.9" at 100 yards,
12.6" at 150 yards
Load "AM22" MV 1200fps drift 1.3" at 50 yards, 4.9" at 100 yards,
10.6" at 150 yards
Load "810" MV 1240fps drivt 1.4" at 50 yards, 5.1" at 100 yards,
10.9" at 150 yards
Note that the UM22 has *more* drift than the faster AM22, while the
AM22 has *less* drift than the faster 810.
Source http://www.federalpremium.com/products/rimfire.aspx
Wayne
Not saying that you are wrong, but I don't follow the logic. The slower
bullet still spends more time in the air. Wouldn't the trans sonic
instability simply add to random error rather than drift?
--Wayne
snakehunter
wrote:
> ...
It is not the weight of the projectile that determines its drift. It
is the ballistic coefficient.
Bob Holtzman
#<<Is it possiable the slower bullet has less wind drift than the
# faster one at low velocities.>>
#
# Sometimes yes, sometimes no...
#
# Comparing 3 Federal loads, all with 40gr. bullets, we see these wind
# drift amounts, in a 10mph wind:
#
# Load "UM22" MV 1080fps drift 1.6" at 50 yards, 5.9" at 100 yards,
# 12.6" at 150 yards
# Load "AM22" MV 1200fps drift 1.3" at 50 yards, 4.9" at 100 yards,
# 10.6" at 150 yards
# Load "810" MV 1240fps drivt 1.4" at 50 yards, 5.1" at 100 yards,
# 10.9" at 150 yards
#
# Note that the UM22 has *more* drift than the faster AM22, while the
# AM22 has *less* drift than the faster 810.
Compare UM22, 711B, and 922A. They are all listed at 1080 fps muzzle
velocity yet the 100 yd drift is 4.2" for 711B and 5.9" for the other
two. The down range velocity of 711B is greater than the others. This
would seem to bear out everyone's intuitive opinion that the longer time
of flight means more wind drift, however the velocity loss difference is
not due to a difference in muzzle velocity (note that they are the same)
but more probably due to differences in bullet form factor. The key here
is that time of flight plays a role *as long as the bullet stays out of
the trans-sonic region*. All current .22rf match ammo I'm aware of is
subsonic for the reason I've noted.
Comments?
--
Bob Holtzman
AF9D 8760 0CFA F95A 6C77 E125 BF90 580F 8D54 9279
"If you think you're getting free lunch,
check the price of the beer"
Bob Holtzman
# Ralph Mowery wrote:
#
# # Is it possiable the slower bullet has less wind drift than the faster one
#
# Think of it this way: There is a constant wind at 90 degrees across
# the path of the bullets. The slower bullet takes longer to get to the
# target, so it has a longer push from the crosswind.
It's surprising how often intuition is wrong.
--
Bob Holtzman
AF9D 8760 0CFA F95A 6C77 E125 BF90 580F 8D54 9279
"If you think you're getting free lunch,
check the price of the beer"
Gunny_2009
"Ralph Mowery" <rmower...@earthlink.net> wrote in message
news:h1ub81$m20$1...@news.albasani.net...
# I was looking at an American Hunter magazine and in it was a quiz. They
# stated that if you shot a low velocity and a high velocity 22 rimfire the
# lower velocity would have less wind drift. They also mentioned the higher
# speed center fires had the opposit effect as they were supersonic.
#
# Is it possiable the slower bullet has less wind drift than the faster one
at
# low velocities.
Other than for some strange anomalies occasionally, think of it as if you
were swimming across a river. The faster you swim, the less downriver you
will drift before reaching the far side. "In general", the slower the
projectile, the longer it is exposed to the crosswind and more it will be
deflected.
Jim
news:h1vq8a$leb$1...@news.albasani.net...
# Ralph Mowery wrote:
#
# one
#
# Think of it this way: There is a constant wind at 90 degrees across
# the path of the bullets. The slower bullet takes longer to get to the
# target, so it has a longer push from the crosswind.
#
# Doug Chandler
Increased mass/more efficient BC results in less deflection....there's a lot
more to ballistics than time of flight.
There's a few free ballistic programs available that will do side by side
comparisons.
Michael Medley
supersonic
counterparts, because they lack the influence of transonic turbulence
when they are slowing down.
With respect to wind drift, the faster the projectile, the less time
cross
winds will have to affect it. The trick is to maintain supersonic
velocity
all the way to the target.
Larry The Snake Guy
# Other than for some strange anomalies occasionally, think of it as if you
# were swimming across a river. The faster you swim, the less downriver you
# will drift before reaching the far side. "In general", the slower the
# projectile, the longer it is exposed to the crosswind and more it will be
# deflected.
That might be a useful analogy for subsonic rounds, but a supersonic
bullet is more like swimming so fast the water is never actually
touching the sides of your body. A trans-sonic round is somewhere in
between. The water is touching your body, but it's swirling all over
the place and maybe just touching the front of your body. Less obvious
things can happen then like the current rotating your body in a
direction of the current.
That may still be overly simplistic or just mostly wrong, but the
point is it's not quite as simple as is sounds. Ask Chuck Yaeger.
Bob Holtzman
#
# Not saying that you are wrong, but I don't follow the logic. The slower
# bullet still spends more time in the air. Wouldn't the trans sonic
# instability simply add to random error rather than drift?
Instability = increased wind sensitivity.
--
Bob Holtzman
AF9D 8760 0CFA F95A 6C77 E125 BF90 580F 8D54 9279
"If you think you're getting free lunch,
check the price of the beer"
Rubaiyat of Omar Bradley
# the velocity loss difference is
# not due to a difference in muzzle velocity (note that they are the same)
# but more probably due to differences in bullet form factor.
The phrase is "ballistic coefficient". It means the average density
times the length, divided by the drag coefficient.
<<everyone's intuitive opinion that the longer time of flight means
more wind drift>>
While this works for practical purposes in the real world, it is not
actually technically correct. The amount of wind drift corresponds to
the relative amount of velocity lost, not the time of flight.
Bob Holtzman
# On Jun 25, 5:26 pm, Bob Holtzman <hol...@sonic.net> wrote:
# # the velocity loss difference is
# # not due to a difference in muzzle velocity (note that they are the same)
# # but more probably due to differences in bullet form factor.
#
# The phrase is "ballistic coefficient". It means the average density
# times the length, divided by the drag coefficient.
#
#<<everyone's intuitive opinion that the longer time of flight means
# more wind drift>>
#
# While this works for practical purposes in the real world, it is not
# actually technically correct. The amount of wind drift corresponds to
# the relative amount of velocity lost, not the time of flight.
Close. actually wind sensitity is proportional to the lag time which
IIRC is defined as the difference velocity loss in air vs velocity loss
in a vacuum. Ballistic coefficient and form factor come into play.
--
Bob Holtzman
AF9D 8760 0CFA F95A 6C77 E125 BF90 580F 8D54 9279
"If you think you're getting free lunch,
check the price of the beer"
DougC
# #<<everyone's intuitive opinion that the longer time of flight means
# # more wind drift>>
# #
# # While this works for practical purposes in the real world, it is not
# # actually technically correct. The amount of wind drift corresponds to
# # the relative amount of velocity lost, not the time of flight.
#
# Close. actually wind sensitity is proportional to the lag time which
# IIRC is defined as the difference velocity loss in air vs velocity loss
# in a vacuum. Ballistic coefficient and form factor come into play.
Now everybody is getting confused. Wind drift does not necessarily
slow the bullet- a tail wind might help sustain it. Velocity loss in
a vacuum is zero.
But most likely none of us will ever shoot in outer space.
There is a difference between a wind, which can be compensated for,
and the erratic disruption of crossing the sound barrier, which is
unpredictable. Two different things.
Doug Chandler
Brian Whatcott
This whole thread has been pretty unsatisfying. The majority wanted to
assert the "slower is more drift" common sense idea - which happens to
be wrong for bullets flying near the speed of sound. The ballistic data
is widely available on line - some contributors even extracted parts -
but that did not correct the following responses.
Pity!
Brian W
Ralph Mowery
"Brian Whatcott" <bet...@sbcglobal.net> wrote in message
news:h280km$na2$1...@news.albasani.net...
#
# This whole thread has been pretty unsatisfying. The majority wanted to
# assert the "slower is more drift" common sense idea - which happens to
# be wrong for bullets flying near the speed of sound. The ballistic data
# is widely available on line - some contributors even extracted parts -
# but that did not correct the following responses.
# Pity!
#
# Brian W
#
Yes, it has. As the OP all I wanted to know if the slow speed 22 would
drift more than the faster speed one as the answer to the question in the
magazine stated.
I guess that wind forces can act differant on slower bullets if they are
subsonic than they will if the bullet is supersonic.
Maybe even the slower spinning bullet due to speed has some effect that is
not ovious to most.
I know all about the minor bump as the bullet drops below the speed of
sound and such. I do not care if the bullet hits the target, just the
ammount of drift. I would assume the average change of direction when
dropping below the speed of sound wold be accounted for.
Bob Holtzman
# Bob Holtzman et al wrote:
#
# # # more wind drift>>
# # #
# # # While this works for practical purposes in the real world, it is not
# # # actually technically correct. The amount of wind drift corresponds to
# # # the relative amount of velocity lost, not the time of flight.
# #
# # Close. actually wind sensitity is proportional to the lag time which
# # in a vacuum. Ballistic coefficient and form factor come into play.
#
# Now everybody is getting confused. Wind drift does not necessarily
# slow the bullet- a tail wind might help sustain it.
I don't believe I said it did.
# Velocity loss in a vacuum is zero.
True, which leads to the definition I stated.
# There is a difference between a wind, which can be compensated for,
# and the erratic disruption of crossing the sound barrier, which is
# unpredictable. Two different things.
You lost me. Where did I say it wasn't?
--
Bob Holtzman
AF9D 8760 0CFA F95A 6C77 E125 BF90 580F 8D54 9279
"If you think you're getting free lunch,
check the price of the beer"
Bob Holtzman
#
# This whole thread has been pretty unsatisfying. The majority wanted to
# assert the "slower is more drift" common sense idea - which happens to
# be wrong for bullets flying near the speed of sound. The ballistic data
# is widely available on line - some contributors even extracted parts -
# but that did not correct the following responses.
# Pity!
Agreed. "My mind is made up. Don't confuse me with facts." After all,
equations are just for them ponty headed intalekchools.
--
Bob Holtzman
AF9D 8760 0CFA F95A 6C77 E125 BF90 580F 8D54 9279
"If you think you're getting free lunch,
check the price of the beer"
mehrdad ghassempoory
It a bullet is heavier its sideways acceleration is slower. If the
bullets have the same sideways profile, the heavy and the light
bullets are pushed sideways by the same force. However th elower
acceleration of the heavy bullet will show more inertia and less
drift.
Misifus
# snakehunter wrote:
#
# It a bullet is heavier its sideways acceleration is slower. If the
# bullets have the same sideways profile, the heavy and the light
# bullets are pushed sideways by the same force. However th elower
# acceleration of the heavy bullet will show more inertia and less
# drift.
#
This is not a case of mass and acceleration, but rather a case where the
sea through which bullet travels is moving sideways. This is not a
constant force accelerating the bullet sideways, but more like a boat
crossing a river. If the boat is steered straight toward the opposite
bank, the movement of the water will take the boat downstream as it
travels. The same is true of the bullet, as the medium through which
the bullet travels is moving, so is the bullet. The longer the bullet
travels through this moving medium, the farther it travels sideways, and
the greater the windage error.
This has already been established. Clearly, the turbulence associated
with the transition through the speed of sound affects this
relationship, as has also been established. If this were simple....
However, the empirical evidence has been shown. That trumps all the
theories.
-Raf
--
Misifus-
Rafael Seibert
Photos: http://www.flickr.com/photos/rafiii
home: http://www.rafandsioux.com
Ralph Mowery
"Jim" <jp...@cox.net> wrote in message news:h2114u$dqs$1...@news.albasani.net...
# Increased mass/more efficient BC results in less deflection....there's a
# lot
# more to ballistics than time of flight.
#
# There's a few free ballistic programs available that will do side by side
# comparisons.
#
I will agree there may be a lot more to it. I ran several calculations on
some intenet programs. Using the same bullet and a 10 mile wind and 100
yards for the data. Used 800 fps and it was about 2.7 inches of deflection,
used 1400 fps and got 4.8 inches. Ok so far. Then dropped to 200 fps and
got about a negative 68 inches.
Now if that bullet can go the opposit direction the wind is pushing it by
about 5 feet I would like to see that. Several programs showed the same
thing. So much for believing the calculations they are using.
I do not know much about wind drift programs, but assume they may be taking
some short cuts by leaving a few things out. I have done enough
calculactions in electronics to know that most of the time you can use
general formulars and get close enough most of the time. However sometimes
when you get to critical areas or at the extream ranges, you must include
all the factors.
snakehunter
wrote:
> ...
That is only true if the heavier bullet has a higher ballistic
coefficient.
clarkm...@gmail.com
terrible groups at 100 yards.
It has been said that is because somewhere between 50 yards and 100
yards the the bullet goes sub sonic, and looses it's way.
It is a satisfying answer, because it means it's not my fault.
Wayne
Did the 1400 fps drop to subsonic during flight? If not, why the extra
deflection?
--Wayne
Larry The Snake Guy
# Velocity loss in a vacuum is zero.
If your range is sufficiently far from the nearest planet, yes. Near
the surface of the earth, velocity is a vector that changes in it's
vertical component due to gravity. For a bullet traveling in a
ballistic arc in a vacuum, velocity will decrease for the first half
(roughly) of the flight and increase for the second half.
I doubt any ballistics program you find on the web is going to
integrate that change, and I have no idea whether it's significant
over rifle bullet ranges (I doubt it),
Jim
# Using the same bullet and a 10 mile wind and 100
# yards for the data. Used 800 fps and it was about 2.7 inches of
# deflection,
# used 1400 fps and got 4.8 inches. Ok so far. Then dropped to 200 fps and
# got about a negative 68 inches.
#
Irritating thing about computers....the results you get are only as good as
the data fed them.
I can't think of too many rifle or pistol rounds putt-putting along at
200fps. I doubt the programmer did either. Within practical limits results
are determinable.
Louis Boyd
# I can get great groups at 50 yards with a 22LR rimfire, but get
# terrible groups at 100 yards.
#
# It has been said that is because somewhere between 50 yards and 100
# yards the the bullet goes sub sonic, and looses it's way.
#
# It is a satisfying answer, because it means it's not my fault.
Have you tried subsonic ammo? If it starts subsonic it can't go
transsonic at any distance. It will have more drop but it will likely
have much better accuracy, at least if it stabilizes with your barrel
twist. Try more than one brand.
Wayne
<clarkm...@gmail.com> wrote in message
news:h2bram$3ft$1...@news.albasani.net...
#I can get great groups at 50 yards with a 22LR rimfire, but get
# terrible groups at 100 yards.
#
# It has been said that is because somewhere between 50 yards and 100
# yards the the bullet goes sub sonic, and looses it's way.
#
# It is a satisfying answer, because it means it's not my fault.
#
My buddy (who may not be right, but knows WAY more on the subject than I
do)...says that when the bullet slows down to the transsonic region, bullet
drag increases, and then decreases significantly after passing to subsonic.
Thus, the most wind drift would occur if the round goes through the
trans-sonic region well before striking the target. FWIW....
--Wayne
Wayne
"Louis Boyd" <bo...@apt0.sao.arizona.edu> wrote in message
news:h2cstl$f8p$1...@news.albasani.net...
# clarkm...@gmail.com wrote:
# # I can get great groups at 50 yards with a 22LR rimfire, but get
# # terrible groups at 100 yards.
# #
# # It has been said that is because somewhere between 50 yards and 100
# #
# # It is a satisfying answer, because it means it's not my fault.
# Have you tried subsonic ammo? If it starts subsonic it can't go
# transsonic at any distance. It will have more drop but it will likely
# have much better accuracy, at least if it stabilizes with your barrel
# twist. Try more than one brand.
#
Yeah, and funny how my Savage MKII and Kimber 82 both like Lapua ($) ever
so much better than WalMart Remington 550 bulk.
:)
--Wayne
Bob Holtzman
# On Jun 25, 5:26 pm, Bob Holtzman <hol...@sonic.net> wrote:
# # the velocity loss difference is
# # not due to a difference in muzzle velocity (note that they are the same)
# # but more probably due to differences in bullet form factor.
#
# The phrase is "ballistic coefficient". It means the average density
# times the length, divided by the drag coefficient.
I know the term. I used form factor because the coefficient of drag is
related to it.
Bob Holtzman
Bob Holtzman
# deflection?
Since the range was stated to be 100 yds, I guarantee it went subsonic
short of the target.
--
Bob Holtzman
AF9D 8760 0CFA F95A 6C77 E125 BF90 580F 8D54 9279
"If you think you're getting free lunch,
check the price of the beer"
Tom Line
move the projectile increases. Instead of swimming through a river of
water, you're suddenly swimming a river of molasses flowing at the same
speed.
Bob Holtzman
# Does the sonic boom compress the atmosphere so much that it's effect to
# move the projectile increases. Instead of swimming through a river of
# water, you're suddenly swimming a river of molasses flowing at the same
# speed.
That's not a bad way of thinking of it. The bullet is subjected to
increased drag in the transonic region. That increases velocity loss
which means greater lag time. Drift is proportional to lag time (so
sayeth the aerodynamicists). You will find that almost all match grade
ammo (true match grade...not what's printed on the box) is loaded
subsonic.
--
Bob Holtzman
AF9D 8760 0CFA F95A 6C77 E125 BF90 580F 8D54 9279
"If you think you're getting free lunch,
check the price of the beer"
jaf
No. The shock wave causes instability.
The spin rate of the bullet needed for stability is different at supersonic speeds.
Different at subsonic speeds.
And different at transonic speeds.
Obviously the spin rate can't be regulated in flight although it does slow with time.
Life is a compromise.
John
Bob Holtzman
# Tom,
# No. The shock wave causes instability.
# The spin rate of the bullet needed for stability is different at
# supersonic speeds.
# Different at subsonic speeds.
# And different at transonic speeds.
True, but the aerodynamists I talked to still claim the lag time is the
causative factor.
--
Bob Holtzman
AF9D 8760 0CFA F95A 6C77 E125 BF90 580F 8D54 9279
"If you think you're getting free lunch,
check the price of the beer"
Bob Holtzman
# On 2009-07-17, jaf <jaf....@myfairpoint.net> wrote:
# # Tom,
# # No. The shock wave causes instability.
# # The spin rate of the bullet needed for stability is different at
# # supersonic speeds.
# # Different at subsonic speeds.
# # And different at transonic speeds.
#
# True, but the aerodynamists I talked to still claim the lag time is the
# causative factor.
Sorry to follow up to my own post, but the word I meant to type was
ballisticians, not aerodynamists.
--
Bob Holtzman
If you think you're getting free lunch,
check the price of the beer!
Gunny_2009
"Bob Holtzman" <hol...@txpwlcox.net> wrote in message
news:h3r08v$rpp$1...@news.albasani.net...
# On 2009-07-17, jaf <jaf....@myfairpoint.net> wrote:
# # Tom,
# # No. The shock wave causes instability.
# # The spin rate of the bullet needed for stability is different at
# # supersonic speeds.
# # Different at subsonic speeds.
# # And different at transonic speeds.
#
# True, but the aerodynamists I talked to still claim the lag time is the
# causative factor.
But is that true only in the northern hemisphere and when shooting north to
south? What about in Australia and shooting east to west? LOL
Wayne
"jaf" <jaf....@myfairpoint.net> wrote in message
news:h3qn19$frm$1...@news.albasani.net...
# Tom,
# No. The shock wave causes instability.
# The spin rate of the bullet needed for stability is different at
# supersonic speeds.
# Different at subsonic speeds.
#
# Obviously the spin rate can't be regulated in flight although it does slow
# with time.
#
# Life is a compromise.
#
# John
#
The transition between supersonic and subsonic does cause instability.
However, wind drift is a different animal. My understanding is that drag is
substantially greater just above the speed of sound than the drag just below
the speed of sound. In rounds such as 22LR, that drag causes a rapid
deceleration on supersonic bullets, and substantial wind drift occurs.
Random tumbling of the bullet also occurs.
At least, that's the way a local menso explained it to me....... :)
--Wayne
jaf
# But is that true only in the northern hemisphere and when shooting north to
# south? What about in Australia and shooting east to west? LOL
#
No.
In Australia everything is upside-down so there are no effects in the transonic range! ;<)
John
brian whatcott
# # But is that true only in the northern hemisphere and when shooting north to
# # south? What about in Australia and shooting east to west? LOL
# #
#
# No.
# In Australia everything is upside-down so there are no effects in the transonic range! ;<)
#
#
# John
Well, Yes! The bullets fall upwards there, doncha know?
Brian W
Wayne Richards
<hol...@cox.net> wrote:
#On 2009-07-17, Tom Line <tl...@iglou.com> wrote:
## Does the sonic boom compress the atmosphere so much that it's effect to
## move the projectile increases. Instead of swimming through a river of
## water, you're suddenly swimming a river of molasses flowing at the same
## speed.
#
#That's not a bad way of thinking of it. The bullet is subjected to
#increased drag in the transonic region. That increases velocity loss
#which means greater lag time.
I'm not sure what you mean by lag time. The only definition I could
find was related to online gaming. However, I believe what you are
calling lag time is the time it takes for the bullet to reach the
target after the gun is fired. If this is not the case, please
correct me.
Increased velocity loss DOES NOT mean increased "lag time". For
example, if a bullet is fired at 2,500 fps, and hits the target at
2,000 fps, the "lag time" will be far less than if a bullet is fired
at 1000 fps and hits the target at 900 fps, holding the distance
constant.
#Drift is proportional to lag time (so
#sayeth the aerodynamicists).
You are correct in saying that drift is proportional to "lag time".
However, "lag time" is NOT a function of just velocity loss. If that
were the case (it's not) you could tell me what the "lag time" was if
I gave you just the velocity loss. Obviously, that is not true.
In general, if a bullet is fired at a higher velocity, the "lag time"
will be less than if the same bullet is fired at a lower velocity and
the distance to the target is the same. Anything other result is
simply impossible.
It's pretty trivial to prove this concept with mathematically but you
can think about it like this:
"Lag time" is a function of the average velocity of the bullet during
it's flight. Velocity loss over a given time period is a function of
the velocity of the bullet at the start of that time period. That
means the velocity loss of the a bullet traveling at X fps over a time
period Y milliseconds will be the same regardless of what the bullet
was doing prior to the start of that time period. If the initial
velocity of the bullet is higher, then the average velocity of the
bullet must be higher, therefore, the "lag time" is lower.
#You will find that almost all match grade
#ammo (true match grade...not what's printed on the box) is loaded
#subsonic.
Well, that is not really true. Most rifle match ammo is loaded to
supersonic velocities. 5.56, .308, 50 BMG are some examples. The
accuracy gain for subsonic ammo has nothing to do with "lag time", it
has to do with the turbulence the bullet experiences going from
supersonic to subsonic velocities. In general for match ammo, if you
fire a bullet at supersonic velocities you want it to hit the target
at supersonic velocities, to avoid the turbulent transition from
supersonic to subsonic velocities. If you fire a bullet at supersonic
velocities, the "lag time" will always be less than if you fire the
same bullet over the same distance at subsonic velocities.
Louis Boyd
# In general, if a bullet is fired at a higher velocity, the "lag time"
# will be less than if the same bullet is fired at a lower velocity and
# the distance to the target is the same. Anything other result is
# simply impossible.
You are confusing time lag with time of flight. They are not the same
thing. The statement above is simply not true.
Lag time as used in ballistics is simple to state:
Lag time is time a bullet actually takes to travel from the muzzle to
the target minus the time it would take for the bullet to reach the
target if there were no atmospheric drag.
Time lag can also be stated as the additional time atmospheric drag
causes a bullet to take to reach the target.
Stated as an equation:
Lag_time = ( (time of flight) - ( target_distance/muzzle_velocity))
How wind deflection relates to time lag is also very simple:
Wind deflection at the target = crosswind_velocity * lag_time.
Notice thats an equal sign. It's not just proportional.
It's that simple! It's called Didion's equation. He was a French
ballistician who discovered the relation and published it in 1859. It
is only required that consistent units for used for the wind velocity,
bullet velocity and the distance to the target. such as feet and seconds
or meters and seconds. What units are used doesn't matter. Furlongs
and fortnights would work.
At least to the first order the equation is correct for all symmetrical
projectiles (non lifting) whether the have their own power source (like
an unguided rocket) or not and whether they're fin or spin stabilized.
The actual time of flight may be measured directly or calculated.
Calculating actual time of flight is where drag functions, ballistic
coefficients and air density become useful, But you only need to know:
1 Target distance
2. muzzle velocity
3 Crosswind velocity
4. actual time of flight (measured or calculated)
to correctly determine a bullets crosswind deflection.
The equations for headwind or tailwind components are separate.
Second order effects are related to the time it takes a spinning or fin
stabilized projectile to align itself into the wind and effects related
to a motion mutually perpendicular to the bullet direction and the
crosswind direction. For practical purposes however Didion's equation
works very well. For a full mathematical description of Didion's
equations, equations for head and tail winds, and the second order
effects see "Modern Exterior Ballistics" by Robert L. McCoy. McCoy
was a researcher at the US Army Aberdeen Proving grounds. He also
provided the equations which are use in most ballistics computer
programs in use today.
Bob Holtzman
# example, if a bullet is fired at 2,500 fps, and hits the target at
# 2,000 fps, the "lag time" will be far less than if a bullet is fired
# at 1000 fps and hits the target at 900 fps, holding the distance
# constant.
Your definition of lag time is incorrect. What you're talking about is
time of flight. Search on "lag time + ballistics" and one of the many
hits you get is :
http://www.exteriorballistics.com/ebexplained/4th/532.cfm
#
# #Drift is proportional to lag time (so
# #sayeth the aerodynamicists).
# You are correct in saying that drift is proportional to "lag time".
# However, "lag time" is NOT a function of just velocity loss. If that
# were the case (it's not) you could tell me what the "lag time" was if
# I gave you just the velocity loss. Obviously, that is not true.
#
# In general, if a bullet is fired at a higher velocity, the "lag time"
# will be less than if the same bullet is fired at a lower velocity and
# the distance to the target is the same. Anything other result is
# simply impossible.
That would be true *if* your definition of lag time was correct.
#
# It's pretty trivial to prove this concept with mathematically but you
# can think about it like this:
# "Lag time" is a function of the average velocity of the bullet during
# it's flight. Velocity loss over a given time period is a function of
# the velocity of the bullet at the start of that time period. That
# means the velocity loss of the a bullet traveling at X fps over a time
# period Y milliseconds will be the same regardless of what the bullet
# was doing prior to the start of that time period. If the initial
# velocity of the bullet is higher, then the average velocity of the
# bullet must be higher, therefore, the "lag time" is lower.
#
# #You will find that almost all match grade
# #ammo (true match grade...not what's printed on the box) is loaded
# #subsonic.
# Well, that is not really true. Most rifle match ammo is loaded to
# supersonic velocities. 5.56, .308, 50 BMG are some examples.
Read the subject line. What's under discussion here is .22 rf ammo!
# The
# accuracy gain for subsonic ammo has nothing to do with "lag time", it
# has to do with the turbulence the bullet experiences going from
# supersonic to subsonic velocities.
Accuracy is not the subject here. Wind drift is. They are *not* the
same thing. Furthermore, your assertion is incorrect. Read the link I
cited among the others the search I suggested yields.
# In general for match ammo, if you
# fire a bullet at supersonic velocities you want it to hit the target
# at supersonic velocities, to avoid the turbulent transition from
# supersonic to subsonic velocities. If you fire a bullet at supersonic
# velocities, the "lag time" will always be less than if you fire the
# same bullet over the same distance at subsonic velocities.
*sigh*...read.
--
Bob Holtzman
AF9D 8760 0CFA F95A 6C77 E125 BF90 580F 8D54 9279
"If you think you're getting free lunch,
check the price of the beer"
robert...@gmail.com
# I was looking at an American Hunter magazine and in it was a quiz. They
# stated that if you shot a low velocity and a high velocity 22 rimfire the
# lower velocity would have less wind drift. They also mentioned the highe
# speed center fires had the opposit effect as they were supersonic.
# Is it possiable the slower bullet has less wind drift than the faster one at
# low velocities.
In .22 rimfire only the drift is a function of the time of flight in the atmosphere
vs the time of flight in a vacuum. The difference in time for the sub sonic is
percentage wise--less than the percentage of difference in the super sonic. It
is this "difference" which determines drift in .22 rimfire.
Just Wondering
# On Wednesday, June 24, 2009 at 6:01:21 PM UTC-5, Ralph Mowery wrote:
# # I was looking at an American Hunter magazine and in it was a quiz. They
# # stated that if you shot a low velocity and a high velocity 22 rimfire the
# # lower velocity would have less wind drift. They also mentioned the highe
# # speed center fires had the opposit effect as they were supersonic.
# # Is it possiable the slower bullet has less wind drift than the faster one at
# # low velocities.
#
# In .22 rimfire only the drift is a function of the time of flight in the atmosphere
# vs the time of flight in a vacuum. The difference in time for the sub sonic is
# percentage wise--less than the percentage of difference in the super sonic. It
# is this "difference" which determines drift in .22 rimfire.
#
That doesn't make sense. Wind drift is a function of the time a
projectile is subject to a cross wind, not the projectile's velocity.
One big culprit affecting a .22LR's accuracy is crossing the sound
barrier. Most popular.22LR cartridges have muzzle velocities in the
1200-1400 fps range which makes them supersonic, but barely so. (The
speed of sound varies with temperature, elevation etc. but think of it
as around 1100 fps). A supersonic .22LR projectile will go subsonic
somewhere between 80-120 yards depending on its initial velocity.
Funny things happen to a projectile when it crosses the sound barrier.
https://loadoutroom.com/thearmsguide/long-range-shooting-external-ballistics-transonic-region/
This can make a .22LR's long range accuracy problematic. Match grade
..22LR ammo is almost always subsonic not because of anything to do with
wind drift, but to avoid the turbulence that comes with crossing the
sound barrier.