ANOTHER TUNE QUESTION BUT......

[Bill Norris]

We all know atmospheric conditions affect the tune of our rifles whether we are using a tuner or simply relying on the plain old powder charge vs. seat depth but, IS OUR TUNE MORE AFFECTED BY ATMOSPHERIC CONDITIONS between the chamber and muzzle or between the muzzle and target or is it equal ? Interesting to hear opinions.

 

[gunsandgunsmithing]

Once the bullet is gone, tune is over. Ya got what ya got....by any tuning method.

 

[ELR LVR]

We all know atmospheric conditions affect the tune of our rifles whether we are using a tuner or simply relying on the plain old powder charge vs. seat depth but, IS OUR TUNE MORE AFFECTED BY ATMOSPHERIC CONDITIONS between the chamber and muzzle or between the muzzle and target or is it equal ? Interesting to hear opinions.

I don't believe inside the bore matters much
Unless there is a lot of humidity in the bore creating more resistance for the bullet to move. Which would show as pressure signs.
If we think about it, the bullet is leaving the case and sealing the bore behind it
separated from the atmosphere.
In effect the powder in the case is creating its own atmosphere behind the bullet
Temp would be my only consideration in how it affects the powder burn.
Since Temp is the only thing that can transfer into the cartridge from outside.
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Therefore, I believe any atmoshperic conditions affect the bullet AFTER it leaves the bore
on it's way to the target

 

[dusterdave173]

Very interesting
Yesterday I shot an ARA 22 match--I took a great lot of ammo that has been doing wonderful and winning in the last few matches--but..conditions were awful--humidity 88 % dripping wet off of the rifles and that ammo shot like mouse poop in dresser drawer--all over the place! I pulled out another lot of ammo and wham! Tight groups and a good day--
So..Did the conditions mess with my killer ammo? I think darn right it did but scratch my head why the other lot did not seem to mind??

 

[JMayo]

Air thickness the the bullet goes through between barrel and targetmatters. Imo
Inside the barrels seems to be a stretch to me?

 

[R.Morehouse]

I like having some heat in my barrel before going to the record target. I think that matters, would you consider that atmospheric?......I Don't Know......The target seems to like it.

Regards
Rick

 

[CharlieNC]

Shoot a charge weight ladder, you will observe an overall increase in poi coupled with the flatter regions (nodes) where the barrel upswing offsets. Temperature affects the effect of velocity on drop, and temperature affects velocity (barrel time). The net effect depends on the exact combination.

 

[Bill Norris]

Seems like from the muzzle to the target is the belief. It would make sense that the round is sealed and placed within the chamber which again creates another barrier from the elements.

 

[Clancy]

I know that while it rarely rains here, my tune goes out the window when it does- until the humidity subsides. I’d love to know exactly why.

 

[hoz53]

Seems like from the muzzle to the target is the belief. It would make sense that the round is sealed and placed within the chamber which again creates another barrier from the elements.

interesting thought Bill— i would send Litz a PM and see if he would post in this thread. i imagine this answer is in one of his books i have but i dont wanna take the time to look it up.

 

[Jayplace]

This is different than the question being asked, but what about the conditions when the cartridge was being loaded? Wouldn't higher or lower humidity or even the atmospheric conditions affect what happens when the round is fired. Just high humidity would lower the oxygen content within the round.

 

[ELR LVR]

I know that while it rarely rains here, my tune goes out the window when it does- until the humidity subsides. I’d love to know exactly why.

It should print higher with humid air being less dense.
Does it also spread out?
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I don't get to encounter much of the extreme enviro conditions in Calif.
since it's pretty stable where I live even in the Mtns.
However I have shot long range in the rain at 1000 yds.
My holdover surprisingly was the same as when dry and also coincided with my drop chart.
I was expecting the bullet to be majorly deflected by raindrops
Evidentaly though, the mach wave being pushed in front of the bullet pushes rain drops out of its own way and still strikes the target on point.
I only did that once though just to see what would happen
I dont like letting my nice stuff get all wet so I never followed up to gauge if it was even an inch off at 1000, all I saw was the same elevation was required.
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Storm fronts however I read ...do majorly different things as the pressure is constantly dropping until it equalizes.
I have not yet had a chance to shoot during a storm front as it moves in yet.
I'm Looking forward to that

 

[Bill Norris]

Storm fronts however I read ...do majorly different things as the pressure is constantly dropping until it equalizes.
I have not yet had a chance to shoot during a storm front as it moves in yet.
I'm Looking forward to that

The one time I was shooting in that condition my tuner did not act the same as if it were stable conditions. Had to turn it more than I normally would.

 

[Bill Norris]

This is different than the question being asked, but what about the conditions when the cartridge was being loaded? Wouldn't higher or lower humidity or even the atmospheric conditions affect what happens when the round is fired. Just high humidity would lower the oxygen content within the round.

I believe it would have an affect on the load.

 

[Clancy]

@ELR LVR I can go from a .200-.250 tune and it’ll shoot .280-.350

It happens to all of us around here that I’ve talked to. Humid weather kills us. But, we don’t have to change our load much otherwise.

 

[JFrank]

When I put a load together in winter to early spring, I’ve seen the load go out the top in hot dry air. It’s not much but it does.

 

[Longrange57]

We all know atmospheric conditions affect the tune of our rifles whether we are using a tuner or simply relying on the plain old powder charge vs. seat depth but, IS OUR TUNE MORE AFFECTED BY ATMOSPHERIC CONDITIONS between the chamber and muzzle or between the muzzle and target or is it equal ? Interesting to hear opinions.

Bill, this is a very good and interesting question, but quite possibly few answers. Yes, as Ezell says, after leaving muzzle....you got what you got! I'm in line with that, but this interesting question could be bordering on a question I asked on the competition forum on May 30.
Is it possible that what some refer as dead air and especially the first couple of inches upon exit, have something to do with this issue, as humidity changes?? The various humidity changes when meeting up with spent nitrocellulose gases that weigh much more.... may cause the bullet to get upset a bit easier.

Example: Air den 60F, 1 ATM dry .0763 lb/cf
moist 90% den 60F, 1 ATM .0759 lb/cf
Oxygen same conditions .084 lb/cf
CO2 same conditions .117 lb/cf.....this could very well be 86% of the spent gas along with remaining nitrogen and hydrogen. Hydrogen won't be a big contributor to the weight. see attachment

The spent gas ahead of the bullet meets up with ATM air before leaving the barrel and the density differences due to humidity might possibly be the differences in "tune" we are talking about. This the reason you may have to move the tuner as much as you do or change the load a bit.
My two cents! However, no real answer, but question is a great one!

 

[Bill Norris]

Bill, this is a very good and interesting question, but quite possibly few answers. Yes, as Ezell says, after leaving muzzle....you got what you got! I'm in line with that, but this interesting question could be bordering on a question I asked on the competition forum on May 30.
Is it possible that what some refer as dead air and especially the first couple of inches upon exit, have something to do with this issue, as humidity changes?? The various humidity changes when meeting up with spent nitrocellulose gases that weigh much more.... may cause the bullet to get upset a bit easier.

Example: Air den 60F, 1 ATM dry .0763 lb/cf
moist 90% den 60F, 1 ATM .0759 lb/cf
Oxygen same conditions .084 lb/cf
CO2 same conditions .117 lb/cf.....this could very well be 86% of the spent gas along with remaining nitrogen and hydrogen. Hydrogen won't be a big contributor to the weight. see attachment

The spent gas ahead of the bullet meets up with ATM air before leaving the barrel and the density differences due to humidity might possibly be the differences in "tune" we are talking about. This the reason you may have to move the tuner as much as you do or change the load a bit.
My two cents! However, no real answer, but question is a great one!

Thank you Sir.

 

[Bill Norris]

interesting thought Bill— i would send Litz a PM and see if he would post in this thread. i imagine this answer is in one of his books i have but i dont wanna take the time to look it up.

Didn't find his contact info when I searched for him.

 

[hoz53]

try Bryan Litz Ballistics