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Discussion Starter · #1 ·
This may seem like a stupid question but how much does temperature and humidty affect tragectory, is it negligible?.. I was shooting my 597 today and it was off from where it was last time I shot.. Today was 85 degrees and last time I shot it was maybe 45.High atmospheric pressure today, low last time out. I also went through quite a few rounds and the barrel was pretty hot as well.. I'm not a serious shooter, just a plinker, but I hate to have to mess with the scope everytime I go out. .. Same ammo, same range, same targets, the rifle was not bumped or anything.. It has a 4x Bushnell scope mounted... BTW.. since switching to CCI and Winchester ammo, no more jamming period!......... Anyone want to buy half a brick of Remington golden bullets cheap?.. LOL.. thanks
 

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temp is'nt neccissarily affecting your trajectory..... but, what I see here is at 45 deg, when a round is fired, it builds so much pressure, (lets give this a value of X) now, you said that today you went out it was 85 deg. now thats 40 deg warmer. thats X+ 40 the pressure generated by X+40 will be higher than just X.

now I would assume, that givin same bullets same targets same range, same gun... and this was from a fixed rest, were your shots printing lower?
 

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Discussion Starter · #3 ·
The groups shot HIGHER on the warm day.... There are so many factors involved I'm sure.... I think if I knew them all, it would take the fun out of it.
 

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Higher makes sense to me, more pressure = higher velocity

higher velocity = shorter travel time = less time to fall

the bullet is propelled towards the target by the blast from the powder exploding, this can vary according to environment.

the bullet is also pulled down via gravity wich is always constant in theory and the variences will not make enough difference to measure. :t

it also takes more energy to burn cold powder than hot/warm powder.

just a few of the factors that can come into play

:)
 

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powder exploding :eek:

all is very controlled, it burns at a precise rate, at higher temps, it might burn a little faster, giving you a higher pressure rise. this could then cause the gun to recoil a slight bit more before the round exits the barrel giving you the higher grouping.

it would be interesting to shoot over a chrony on the days in question, and see if there were any veriations in fps. higher velocity could also be causing some of this, BUT, I would think, that if the round was leaving the barrel earlier, the muzzle would be a little lower in the recoil cycle an maybe the groups would be a little lower?

Ah the wonders that are internal ballistics!

TIC, I think, maybe if you look around at some of the books available, you'd be suprized at the fun it can be trying to figure out why that darn little thing just did what it did. :rolleyes: some can get fairly indepth, Yawn, but others may keep your intrest.
 

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Here's a link to an article by Bob Collins on barometric pressure, temp and humidity. JT

http://benchrest.com/csaccuracy/eleybythenumbers.html

An excerpt:

"... dry air has a higher drag on objects moving through, and it slows down bullets like shooting into water. The thing to remember is that barometric pressure is first, then temperature, and then last is relative humidity. Remember we almost always shoot in warm summer months, so the relative humidity is very important."
 

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Discussion Starter · #7 ·
Just as I feared, this gets very involved.. I read the article, thanks for the link.... I plan on keeping my shooting very simple..But it is interesting to see that volumes can and have been written on the subject.
 

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Basic applied physics: Cool air is much more dense than warm air. Cold air molecules are more tightly packed. Therefore, with all other variables remaining constant, projectiles will have higher velocity in warm air because there is less air resistance and less aerodynamic drag. Granted, it won't make a LOT of difference with a rimfire bullet, but it will always make some difference.

Don't get me started on induced and parasitic drag.

Call the home - I'm ready now.:D
 
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