Being fairly new to reloading, I got to thinking about outside temperatures and bullet /powder performance. I do a lot of loading "developement" in the winter and shoot in say 25 to 45 degrees F.
How, if any, will the bullet/powder/performance be when its 65-85 F temps?
Would like to hear your thought.

In the warmer temps, you will get a net gain in velocity and pressure. A good reason to not redline your loads. What it will do to your accuracy, only shooting will give you that answer. With hunting in mind, I've found that the groups don't suffer that much and usually a few clicks of windage/elevation will correct any diviations. I have read posts that say the effects are much more dramatic but I haven't experienced that.

What wasbeeman said. The difference in pressure and velocity between moderately cool ambient temperatures and moderately warm temperatures isn't all that great, but if you do work up loads at <40F then I would recommend rechecking those loads if using them at ambient temps >80F.

Ammo sitting someplace in the sun like the dashboard of your truck can warm up to the point that it might cause you some problems.

quote:

Ammo sitting someplace in the sun like the dashboard of your truck can warm up to the point that it might cause you some problems.

Yeeesss! One time "just to see", I laid a 22-250 round in the sun on the shooting bench. After a couple or three minutes, it blew a primer when I fired it. The rest of the ammo, which was in the shade but with the same air temp, was fine.

Just wondering ?

As we are dealing with pressure, volumes and gas molecules how can it be that Temperature has no effect or little effect? Or do the various gas laws not apply to our craft?


Why would it be that in the reporting of each and every type of ballistic event it is customary to report on ambient temperature and barometric condition?

Perhaps as in many other things ballistics we are quite ignorant of what contributions ambient conditions have on what we do?

powders have burn retardants on them.
some powders are affected by temperature some are not.
the hodgdons extreme line is made to be not temp sensitive.
others just are h-110,blue dot,h-4227.
are affected by temperature.
110 and blue dot by cold and 4227 by heat.
just as an example.
other suffer from ignition issues in the cold.
I-4895 is one of them.
it's just a chemical make-up issue look at imr powders and the pressures they show [and the weight differences] compared to hodgdons powders of the same number.
guess which ones are more likely to burn hotter when subjected to high heat or direct sunlight.

It's not whether the powder itself is temperature resistant, it's once it is chemically converted to a gas that temperature is at issue. The laws of physics dictate this !

PV=nRT this is fundamental to the way guns work. In fact it defines the modern gun .

Without this simple law a gas powered car won't work and a gun powered by a propellant will not propel a projectile down the bore.

quote:

Originally posted by Stonecreek:
Ammo sitting someplace in the sun like the dashboard of your truck can warm up to the point that it might cause you some problems.

I was involved in a research project a couple years ago, involving ammo temp VS pressure/velocity
Baseline temp (ambient) was 55^ish, ammo left on the dashboard (sunny day or defroster on overcast day) was 135^. The difference in velocity averaged in the 125fps range, with the "temp stable" powders being the ones showing the largest increase in velocity (IIRC about 135fps).
The test was also done at -35^ (cooler with dry ice), velocity dropped by about 115fps at that temp.

Thanks all,

Sometime ya just wonder 'bout something and gotta ask.

I will check my loads in warmer weather when it arrives.

Interesting sometimes to observe the differences between the operation of mathematical theories (which basically all physics is), and real life practices.

Though gas expansion and activity IS both pressure and temperture sensitive, in real life practice they seem to be more sensitive (in terms of safety) as either extremes of temp/pressure ranges are approached.

Which is why if a person loads in the mid-portion of designed operating pressures of his powders, temps become relatively less critical.

That's another way of saying...generally if you stay away from top-end and bottom-end loads, temperatures you are likely to be shooting in/at will not be the cause of problems.

If you operate at the extreme edges of ANY endeavor the liklihood of unanticipated and unwanted results increases dramatically with even the slightest environmental changes....every race car driver, pilot, trapeze artist, or even politican knows that.

Hence the development over the ages of the philisophical "golden mean"..."moderation in all things".

If you're looking to load something near max or above max it's best to test that out in the heat of the summer.

Cold weather shooting will reduce velocity some but depends on the load the temperature and the range. IMHO>