Powder sensitivity to temperature

[RBrowning]

I know that temperature is going to have an effect on burn rate, chamber pressure and muzzle velocity. Some powders are going to be more sesnitive than others. Has anyone compiled any data to show how much variation you could expect from the different powders at various temperatures? I see that this could "burn up" a lot of components and I am hoping some powder company, the military or maybe somebody with lots of time and money has already gone through the exercise and published the data.

Thanks for any input.
Rick

 

[Brent]

I have been collecting a bit of data in fairly cold temps with RL25 and have noticed some interesting things I will post after just a little more testing. It's not toooo bad but it is varying with as little as 20 degrees more than I thought it would. 3gr less powder gave the same psi on the Oehler 43 in 20 deg colder temp. If you have a powder in mind I can go back and check some other psi/velocity data and see what I find at the different temps tested with the same loads. I have data on Varget, RL22, RL25, IMR4064, H870, BLC2, IMR4350, IMR4831 and a couple others... some are limited but I'll give you what I can if I have it recorded.

 

[BountyHunter]

Obviously some are more sensitive to temperature than others. Plus you have a lot to lot variance that throws in another curve. Last year there was a lot of RL22 out that was extremely hot versus older and subsequent lots and if you do not test each time you change lots you can get into serious problems potentially. Most guys buy powder in large quantity of same lot, even the new extreme lines of Hodgen that are not supposed to be sensitive to temp changes.

BH

 

[Brent]

My brother still has a can of that HOT lot of RL22 that Hodgdon will replace if he cares too. All my data has lot #'s with it so I only compare the same ones. True, work up with each new one. I had one lot that leaned real slow and another was hotter by about 4.0gr.. The load was 120gr RL22 back down to 116 with the next lot, both were over book max of 108gr using a 400gr X in the 416wby. Talk about burnin ammo working up from 106gr, I went back and bought 5 more pounds of that lot# so I didn't have to again...For a while anyway.

 

[RBrowning]

Right now I am doing my "pre-investment homework". I am still unemployeed which means no money to spend, but lots of time to study and be ready for when I do have some jingle in my pockets.

I am looking at having a 6.5-284 built and will need to get into reloading. Always been a little intimidated by getting into a game where your next mistake might be your last.

But to get into real long range I got to go all the way and start loading my own. I am connsidering the SMK 140, the Hornady V-Max 142 or the Lapua Scenar 138 bullets. The powders that I have seen listed favorably are VV 165, H4831 and IMR4350. Any experience with these powders? Any favorite recipies for the 6.5-284?

Rick

 

[ewallace]

Rick
The H4831SC is what I am using in my 6.5/284 it is not very temperature sensitive. I have shot the same load in 80 Degrees and down to -7 and there is not that much of a difference.
Crow Mag

 

[Mysticplayer]

A rule of thumb says that conventional powders will lose about 2 to 5fps for every deg F of temp loss from the temp the load was done up. The opposite will happen with temp gain.

Today there are temp insensitive powders from Hodgdon and to some degree, Alliant. Viht. powders also have a temp insensitive line (numbers start with a 5). However, I have also heard that this coating deteriorates with time and becomes non effective. Have no hard evidence for this.

Most ball or surplus military stuff I have used is temp sensitive.

I use H4350 and H4831SC Extreme and can say that they don't change much with temp changes. I shoot the same load in winter as in summer (-2C to +35C) and get the same vel, drop and accuracy. Varget started this technology for Hodgdon so is also temp insensitive.

Hope this helps...

Jerry

 

[Brent]

RB,

Jerry has better data than I do for the two powders your looking at that I've used. I just didn't have much temp swing with those powders tested so I can't say.

I do have quite a bit of data for Varget if you'd be using it.