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BC of Airgun Slugs

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It has never ceased to amaze me, how such a tiny bit of drag and/or wind drift affects the path of any projectile. In my (airgun) case, 100 yard shots, at mid-summer temps (90s), amount to 1/2 a mil less hold over, than mid-winter (50s) shots. All this said, we now have the means to measure (via affordable doppler radar) rather small changes in BC during a projectile's path, regardless of the cause. Thus, I suspect a lot of older, tried and true BC programs, will fall out of favor.

I find the technical aspect of this fascinating, even though it's difficult for me to grasp. Sort of like watching documentaries on the universe (which I love) and trying to wrap my head around distances, densities, speed and numbers.

I'm curious on what, if anything air temperature in a gun has to do with bc and/or accuracy. I know that firearm ammo is very sensitive to temperature and shots with cold ammo that have been exposed to low temperatures (late fall weather while hunting for example) are vastly different than hot ammo (cartridges left in a hot car trunk, dashboard, etc.)  The difference between the two trumps all other factors like powder ratio, wind, outside temperature, etc.

Are airguns as affected by hot or cold temps of the air in the reservoir itself? Just a curiosity and I certainly don't want to to take away from the original thread, but airguns have a lot more (to me) variables than a firearm and understanding/limiting them only leads to more consistent results.

The simple answer is, yes. Hot air flows a bit faster than cold (more dense) air. But, we also have to consider that the air cools as it expands, so a ton of other factors have to be considered. I'm sure Bob can address those.

Kevin, what I was alluding to in my previous post was the changing BC of a projectile, as it slows down. I think the most common misconception is, that the BC is the same no matter the velocity, and that simply isn't true!

Being a natural cynic and a person who sees a lot more gray than black and white, I always seem to have the response in my head..."Okay, but what about...?" Different airguns, barrels, elevations, temperatures, air pressures, fps, lubes, projectile designs, etc. can spin me for a loop trying to put the right pieces in the right spots. Granted, that's the challenge of this hobby and it's what makes it hard to reach to upper echelons of performance.

I think you and I are in the same school of thought. if you need more power, get a bigger gun, rather than push the one you have to its limits!

I should add, that the type of hunting and where you hunt, also dictates what you shoot.


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