Hello,
Temps were in the mid 90's at the silhouette shoot yesterday and my shots were high. I wasn't surprised since I did my sighting-in with temps in the mid 60's. But it got me thinking - Is there a rule of thumb or an equation somewhere that says for every X degrees above/below the temperature when you sighted in you will see a drop/rise of Y inches at Z distance?
Sincerely,
MBS
.41557.0
Warm weather ballistics
Moderators: rexifelis, pilkguns
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Questor
In a word, no.
You may want to experiment with Hodgdon's "extreme" powders because they're less sensitive to temperature variations. I remember reading an article on this and was quite amazed to see how some powders are very temperature sensitive and yield velocities significantly higher or lower depending on the temperature.
There's a lot to be said for sighter shots in competition.
.41562.41557
There's a lot to be said for sighter shots in competition.
.41562.41557
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Mako
But, if it's also bright ....
Targets appear smaller in very bright light ... which means that your aim might be higher ... because of sighting in dimmer light/larger target ... which means that you will hit high.
After shooting/sighting on bright targets at the Nationals ... last night night my shots were low on my usual dimmer target.
makofoto-at-earthlink.net.41570.41557
After shooting/sighting on bright targets at the Nationals ... last night night my shots were low on my usual dimmer target.
makofoto-at-earthlink.net.41570.41557
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Warren
Re: Warm weather ballistics
You didn't give us an idea of what breed of silhouette you were shooting - rimfire, centerfire, rifle or pistol, scoped or not...
Assuming you're talking center fire, some powders are temperature sensitive. As a very broad generalization, the faster burning powders are more prone to it. I know I always tried to find a powder that took up the greatest volume in the case (ie the slowest powder suitable for a caliber). That kept pressures down, gave better barrel life and changed the least on hot days.
You can also take precautions such as keeping your ammo out of the sun, maybe keeping it in a small cooler (without the ice packs!).
Predicting how much pressure will increase is pretty well impossible, especially with fast burning powders. I once saw a guy develop a load for 32 S&W Long in a semi auto that worked perfectly in spring. During summer in the competition season he began to get skirt separations, flatened and cratered primers. He was using the fastest burning pistol powder on the market; when he switched to the next slowest, his problems disappeared.
warren-at-pilkguns.com.41573.41557
Assuming you're talking center fire, some powders are temperature sensitive. As a very broad generalization, the faster burning powders are more prone to it. I know I always tried to find a powder that took up the greatest volume in the case (ie the slowest powder suitable for a caliber). That kept pressures down, gave better barrel life and changed the least on hot days.
You can also take precautions such as keeping your ammo out of the sun, maybe keeping it in a small cooler (without the ice packs!).
Predicting how much pressure will increase is pretty well impossible, especially with fast burning powders. I once saw a guy develop a load for 32 S&W Long in a semi auto that worked perfectly in spring. During summer in the competition season he began to get skirt separations, flatened and cratered primers. He was using the fastest burning pistol powder on the market; when he switched to the next slowest, his problems disappeared.
warren-at-pilkguns.com.41573.41557
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Gilberto Castaneda
Re: Warm weather ballistics
:In 10 meter pistol it surely affects, that if you use CO2 and not air, compressed air does not seem affected, I had to rub my pistol with ice after I left it in the car previuos to shooting finals, in the first sighting shots I could see the pellet droping and barely hitting the target OUT of the 1 ring, a few minutes of rubbing returned my Steyr to regular conditions.
Cheers,
Gilberto
ecolypet-at-prodigy.net.mx.41574.41557
Cheers,
Gilberto
ecolypet-at-prodigy.net.mx.41574.41557
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MBS
More details
Hello,
It was smallbore silhouette. I was expecting high shots because warm air is less dense than cool air. Less dense means less aero drag, faster bullet speeds, and ultimately higher shots. And I do believe aero effects are a cubic function so a little difference in air density can have a big affect on bullet drop. There is indeed a lot to be said for sighter shots...
I'll have to dig a little online to find more info. Somebody somewhere must have figured this out.
Thanks,
MBS
.41576.41557
It was smallbore silhouette. I was expecting high shots because warm air is less dense than cool air. Less dense means less aero drag, faster bullet speeds, and ultimately higher shots. And I do believe aero effects are a cubic function so a little difference in air density can have a big affect on bullet drop. There is indeed a lot to be said for sighter shots...
I'll have to dig a little online to find more info. Somebody somewhere must have figured this out.
Thanks,
MBS
.41576.41557
-
Mako
I like V V N320, instead of N310 ...
: You didn't give us an idea of what breed of silhouette you were shooting - rimfire, centerfire, rifle or pistol, scoped or not...
: Assuming you're talking center fire, some powders are temperature sensitive. As a very broad generalization, the faster burning powders are more prone to it. I know I always tried to find a powder that took up the greatest volume in the case (ie the slowest powder suitable for a caliber). That kept pressures down, gave better barrel life and changed the least on hot days.
: You can also take precautions such as keeping your ammo out of the sun, maybe keeping it in a small cooler (without the ice packs!).
: Predicting how much pressure will increase is pretty well impossible, especially with fast burning powders. I once saw a guy develop a load for 32 S&W Long in a semi auto that worked perfectly in spring. During summer in the competition season he began to get skirt separations, flatened and cratered primers. He was using the fastest burning pistol powder on the market; when he switched to the next slowest, his problems disappeared.
makofoto-at-earthlink.net.41578.41573
: Assuming you're talking center fire, some powders are temperature sensitive. As a very broad generalization, the faster burning powders are more prone to it. I know I always tried to find a powder that took up the greatest volume in the case (ie the slowest powder suitable for a caliber). That kept pressures down, gave better barrel life and changed the least on hot days.
: You can also take precautions such as keeping your ammo out of the sun, maybe keeping it in a small cooler (without the ice packs!).
: Predicting how much pressure will increase is pretty well impossible, especially with fast burning powders. I once saw a guy develop a load for 32 S&W Long in a semi auto that worked perfectly in spring. During summer in the competition season he began to get skirt separations, flatened and cratered primers. He was using the fastest burning pistol powder on the market; when he switched to the next slowest, his problems disappeared.
makofoto-at-earthlink.net.41578.41573
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JLK
Warren, what kinda of temperature extreme was involved? Than
: You didn't give us an idea of what breed of silhouette you were shooting - rimfire, centerfire, rifle or pistol, scoped or not...
: Assuming you're talking center fire, some powders are temperature sensitive. As a very broad generalization, the faster burning powders are more prone to it. I know I always tried to find a powder that took up the greatest volume in the case (ie the slowest powder suitable for a caliber). That kept pressures down, gave better barrel life and changed the least on hot days.
: You can also take precautions such as keeping your ammo out of the sun, maybe keeping it in a small cooler (without the ice packs!).
: Predicting how much pressure will increase is pretty well impossible, especially with fast burning powders. I once saw a guy develop a load for 32 S&W Long in a semi auto that worked perfectly in spring. During summer in the competition season he began to get skirt separations, flatened and cratered primers. He was using the fastest burning pistol powder on the market; when he switched to the next slowest, his problems disappeared.
.41583.41573
: Assuming you're talking center fire, some powders are temperature sensitive. As a very broad generalization, the faster burning powders are more prone to it. I know I always tried to find a powder that took up the greatest volume in the case (ie the slowest powder suitable for a caliber). That kept pressures down, gave better barrel life and changed the least on hot days.
: You can also take precautions such as keeping your ammo out of the sun, maybe keeping it in a small cooler (without the ice packs!).
: Predicting how much pressure will increase is pretty well impossible, especially with fast burning powders. I once saw a guy develop a load for 32 S&W Long in a semi auto that worked perfectly in spring. During summer in the competition season he began to get skirt separations, flatened and cratered primers. He was using the fastest burning pistol powder on the market; when he switched to the next slowest, his problems disappeared.
.41583.41573
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javelina
Re: In a word, no. - Sighters?!
: You may want to experiment with Hodgdon's "extreme" powders because they're less sensitive to temperature variations. I remember reading an article on this and was quite amazed to see how some powders are very temperature sensitive and yield velocities significantly higher or lower depending on the temperature.
: There's a lot to be said for sighter shots in competition.
Except you can't say anything about sighter shots in this particular competition because there are none allowed in Silhouette!
.41762.41562
: There's a lot to be said for sighter shots in competition.
Except you can't say anything about sighter shots in this particular competition because there are none allowed in Silhouette!
.41762.41562
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fuck you
Re: Warren, what kinda of temperature extreme was involved?
: : You didn't give us an idea of what breed of silhouette you were shooting - rimfire, centerfire, rifle or pistol, scoped or not...
: : Assuming you're talking center fire, some powders are temperature sensitive. As a very broad generalization, the faster burning powders are more prone to it. I know I always tried to find a powder that took up the greatest volume in the case (ie the slowest powder suitable for a caliber). That kept pressures down, gave better barrel life and changed the least on hot days.
: : You can also take precautions such as keeping your ammo out of the sun, maybe keeping it in a small cooler (without the ice packs!).
: : Predicting how much pressure will increase is pretty well impossible, especially with fast burning powders. I once saw a guy develop a load for 32 S&W Long in a semi auto that worked perfectly in spring. During summer in the competition season he began to get skirt separations, flatened and cratered primers. He was using the fastest burning pistol powder on the market; when he switched to the next slowest, his problems disappeared.
.41972.41583
: : Assuming you're talking center fire, some powders are temperature sensitive. As a very broad generalization, the faster burning powders are more prone to it. I know I always tried to find a powder that took up the greatest volume in the case (ie the slowest powder suitable for a caliber). That kept pressures down, gave better barrel life and changed the least on hot days.
: : You can also take precautions such as keeping your ammo out of the sun, maybe keeping it in a small cooler (without the ice packs!).
: : Predicting how much pressure will increase is pretty well impossible, especially with fast burning powders. I once saw a guy develop a load for 32 S&W Long in a semi auto that worked perfectly in spring. During summer in the competition season he began to get skirt separations, flatened and cratered primers. He was using the fastest burning pistol powder on the market; when he switched to the next slowest, his problems disappeared.
.41972.41583