Temp Sensitivity of Powders

[azsixshooter]

I was curious if anyone knows which powder is less sensitive to extreme changes in temperature? VihtaVuori N160 or RL22? I already have a couple lbs. of N160, I bought it because I couldn't find any RL22 locally but I would have preferred the RL22. If for any reason the N160 doesn't work out then I'm going to try the RL22.

I'm just concerned about the temperature issue because I'll be working this load up in North Phoenix at around 1500 ft @ 100F+ over the summer and early fall and then I'll be elk hunting up around 7000 ft in late November and early December where the temps could be really low. Last time I was up there in late October it was around 18F or so at night/early morning.

I'm definitely going to be testing my loads up there before my hunt when it is colder, but I'd like to try and do as much as possible before then to help minimize any problems I might encounter.

Thanks for any thoughts.

[James R. Burke]

I do use RL-22 for a rifle my wife has. I can not answer your question, but I two would like to know if anyone does know. I live in Michigan, and sometimes work up loads when it is cold, so when it is warm things may change, so I am always rechecking with the temp. Sounds stupid but I would rather be safe than sorry. I just picked up the RL-22 at Scheels if you have one by you. Jim

[res45]

I use Reloader #15 in my 300 Sav. and 54r I know its consistent at all temperature but I don't think RL-22 is. I have no Idea about the N powders nobody with a 100 miles of me sells any of that.

Your best bet would be to go to the powder mfg. web site and contact them,and supply all your load data,firearm to be used and hunting conditions you plan to use it in. Also being that you going to a higher altitude and the air being thinner your POI will change by a few inches so make sure you check your zero.

You may want to check out the Hodgdon web site they make quiet a few Extreme powders that are temperature insensitive to extreme heat and cold.

http://www.hodgdon.com/extreme.html

Here is a free ballistics software program,just punch in your data and it gives you a lot of useful info.
http://www.huntingnut.com/index.php?...=article&sid=3

[azsixshooter]

I wonder how much the thinner air might offset the effects of the cold on combustion? Maybe I'll get lucky and it will help level things off so I get similar velocities.

[Sport45]

The thinner air won't have anything at all to do with combustion or the chamber pressure. The propellent doesn't rely on atmospheric air to burn as the oxidizer is part of the mix. It will burn in a complete vacuum.

The thinner air will have an effect on the bullet after it leaves the barrel.

[azsixshooter]

The thinner air will have an effect on the bullet after it leaves the barrel.

That's what I meant, that maybe despite a slightly lower muzzle velocity due to the cold the bullet might make it up while traveling through the thinner air and have a closer impact velocity to what I'll get down here in Phoenix.

Mostly I'm just curious if either of those two powders stands out as being significantly different in terms of temp sensitivity. I have loaded with AA3100 and N560 but never either of these two.

[Ruger4570]

I lived in Tucson for around 25 years or so which temp wise is about the same as Phoenix. I never experienced any problems with temps, personally, I think the whole issue was develpoed to make an article for some magazine years ago and it has become just anothe "wives tales".
The Military doesn't develop certain rounds for Alaska and others for Iraq. If temps were in reality a problem, you can be sure they would adjust for the locations,, and they don't
It sounds like at 7,000 feet you are going to Flagstaff or Show Low/Pine Top for your hunting. If anything, the colder temps will lower the pressure from Phoenix.
As far at the thinner air, I doubt you could measure the difference on a Chronograph, their built in and unavoidable inaccuracy would be greater.

[azsixshooter]

I'm not too worried about it, I was just wondering if there was a hard, measurable difference between the two powders noted in that regard. If I can get the muzzle velocity I want and decent groups with this N160 I have now I don't really see any reason why I would need to try anything else.

However, if I see pressure signs before I get the desired muzzle velocity or if I can't achieve acceptable groups then I will try the RL22 and see if I can get where I want my MV to be with that. If I work up a good load and then get up and shoot in the cold and find that my POI drops a few inches then that will shorten my MPBR. Also, a loss of velocity at the muzzle will reduce my impact velocity and I want to stay within the bullet manufacturer's suggested range out to whatever MPBR I decide to zero my rifle for. I don't really anticipate any shots over 200 yards and if I get a shot it will probably be under 100 yards, but I still would like to take advantage of these great bullets and get the most out of my hunting load. I'm looking to establish a personal limit that I absolutely won't shoot past. If the animal isn't within it I'll get closer or let him walk.

I've heard that you can expect some loss in velocity in a cold as compared to a hot environment and it seemed to make sense to me. I have also heard that some powders were better than others at minimizing that effect. I don't know much else about it, which is why I posted here. I just started reloading and working over a chrony last year so I'm pretty green. I just want to feel like I considered all angles carefully when I finally settle on a load for my first bull elk hunt.

Plus, handloading is fun and I enjoy the thinking/planning process almost as much as the field testing.

[res45]

Here is some good info and other things that may interest you as well.

http://www.exteriorballistics.com/eb...ned/5th/31.cfm

[azsixshooter]

That's a great link, I love that site and didn't even think to go back and read all of that again. Thanks a million. I found that the Speer book seems to go into some pretty detailed scientific explanations too, but that exterior ballistics site is outstanding.

[Shoney]

I have been unable to find any good articles on the effects of temperature on gunpowders. If someone has any good references, please share.

Hot Weather
I do have anecdotal information from my own personal experiences, but not hard core scientific study. About 40 years ago, when temperature information was nearly nonexistent, even thru the American Rifleman and gun rags. I was on a prairie poodle shoot, with three weapons, 222, 220 Swift, and 6mmRem. Since I had purchased the Swift with my income tax refund, it was early spring and I just had to find the perfect load. Temperatures were in the mid 40°F range, and I worked up a very accurate load near max.

On the poodle shoot, temperature were brutal, between 95°F and 105°F, the first few shots with the Swift did not hit the targets, and I thought I had bumped my scope, so I aimed low but still missed, only to find I could not open the bolt without striking it with the palm of my hand. I examined the cases and discover over pressure signs on all. The next morning it was 75°F and it fired normally.

The temperature rise of 50°F to 60°F made a big difference with the IMR powder I was using.

Cold Weather
For hunting, I developed loads at 20 to 25 F. I have hunted many times at -20 to -45F with a 6mmRem for deer and 222 for coyotes. I noticed a great reduction in terminal effects of the bullets, but experienced no over pressure signs.

Since the weapons were in the cold for a long period before firing, I understand that metal physically shrinks at cold temperatures. However, I do not how cold it has to be before it is a factor. I often wondered if the great reduction in terminal effects of the bullets phenomenon was cause by:
1. the temperature effects on the powders and/or bullet, or
2. if the metal was shrinking the barrel differently from the bullet, to constrict the bullet, or
3. if the bullet was shrinking more than the barrel to give a free-bore effect (this would allow the gas to blow by the bullet).

Any ideas?

[gunner269]

I have no reference material, but do know that British manufacturers always loaded their ammunition that was going to be used in hot climates (Africa, India etc.) to lower pressures, as the heat would push it up to dangerous levels if loaded to standard pressures for the round.

[bayboy]

It seems that most propellants have similar temperature sensitivities. Here is a report that compares IMR type propellants with ball powder.