Powder and Temperature

[flynbenny]

I've spent many hours reading all the powder vs temperature threads on here and many on some other sites. Some good info, but I'd like to go a little further. I think from my reading the least sensitive powders are nailed down fairly well, what I lack is data on the ones that are more sensitive.

 

I'm going to do a project for a class at my university on this, so I can use some help in figuring out the powders that are least, average, and most sensitive to temperature changes. I'd like to know this for both rifle and pistol powder.

 

I'm going to do pistol for the project, I'll probably do rifle later this year or early next year (since my only .223 is still waiting for a stock and glass). While it would be interesting to test a bunch of calibers I'm sticking with 9mm for pistol and .223 for rifle for now. I intend to test a load that just makes 125 PF, and one that is a bit hotter around 145-150, to see if there's any correlation between air space in the case and output. Testing will be done over a chronograph, with ammunition that has been held for a long period of time at specific temperatures. 

 

So far what I have from here and elsewhere:

Pistol: Vihtavuori N3xx and 3Nxx are the least sensitive to temp changes, and Hodgdon Titegroup seems to be average. Some powders are reverse sensitive, e.g. more pressure at lower temps.

Rifle: Hodgdon H322 and Varget are the least sensitive. Rifles also seem to more sensitive than pistols, seems logical to me because the charge in a rifle is much heavier, usually around 5 times or more than a pistol charge.

 

What are your experiences?

[Postal Bob]

On Tuesday, January 23, 2018 at 2:23 PM, flynbenny said:

Pistol: Vihtavuori N3xx and 3Nxx are the least sensitive to temp changes, and Hodgdon Titegroup seems to be average. Some powders are reverse sensitive, e.g. more pressure at lower temps.

 

You are right about the Vihtavuori. But I find titegroup more than average to temp changes, particularly hotter temps. Some of the other powders sensitive to temp extremes, that I've used, are Clays and Bullseye.

[DIYguy]

I load Alliant Power Pistol for my 9mm. Being in MN I've notice different Chrony readings for same loads at different temperatures. I've attached a couple of my Chrony logs for reference. Even more important is the difference I've found in groupings at lower temps. Loads that are zeroed at average temperatures that fifteen rounds will punch a 1-1/2" hole at 10 yards (pistol & rest) open up to 5" spread when ammo is cold. Most noticeable when guns and ammo are in the truck all day in January and then go the range after work. First batch of magazines when cold spray a 5" group. Lay the mags out and warm up to room temp and group tightens substantially. Haven't loaded other powders and tested but do have records and targets documenting Power Pistol.

Reloading_Recipes_1.26.18.pdf

[flynbenny]

Thanks. Anyone have experience with Ramshot Silhouette in temperature extremes?  It is allegedly identical to the old Winchester Action Pistol powder.

 

I just did some 9mm loads with it last night, that stuff metered better than any pistol/shotgun powder I've ever used. Hopefully I will get to the range to fire some next week.

[jason237m]

I have noticed titegroup is more senstive than most to temp changes. 

[dillon]

W231 was notorious for losing velocity at lower temperatures. At a USPSA Nationals held at Reno, NV, I recall over 20 people were bumped from major to minor, shooting 45ACP, as temperatures dropped below the 30s

[flynbenny]

I have figured out my powders for the pistol test. To test the least sensitive powder, I will be using Vihtavuori 3N37. Silhouette will be my unknown, and Titegroup will be used for the most sensitive. 

 

I will be using a coated 124 gr bullet from Eggleston Munitions, and Winchester cases. Test gun will be a Glock 17 running the original barrel.