Temperature and Powder

CrossHairs · Dec 9, 2009

It was cold today, gauge on the car showed 32F as I pulled up to the pistol range at TCGC this morning for a quick shoot. Blue skies, no wind.

I'd loaded some Acc #7 8.7 gr with Berry's 115gr RN 9mm that was the same as I'd shot last weekend with some success. Today....phew, where's that barn door boss?

I was getting a drop of close to 12"-14" at 25 yards, with a recipe, that the weekend before, had given me a pretty flat and accurate trajectory for the same bullet, same distance. So, I did what anyone would do under the circumstance...and threw a couple of mags in my pants pockets and 'snuggled' them somewhere warm while I stood in the sun in a feeble attempt to get some warmth from it.

Next ten rounds started in about the right place, and then, as the cold got to them (I was not rapid firing obviously) each shot got lower and lower!? Mmmm! Next mag...something similar.

Can anyone share their own thoughts on cold weather shooting/reloading and powder choices?

elsie · Dec 9, 2009

This might be a bit helpful:

http://www.exteriorballistics.com/ebexplained/4th/56.cfm

elsie

Cougfan2 · Dec 9, 2009

Elsie; very informative post. When I was working at Hodgdon Powder company, I remember Winchester pulling their Win 630 powder from their lineup. If my old brain remembers correctly, this was also our HS 6 Powder. At that time, all Hodgdon ball powders were repackaged Olin powders. It was found that at extremely low temperatures, that the coating on the outside of the individual ball powder granuals could fracture under extremely low temperatures and create unsafe pressure conditions. Curious if with current powders if extreme cold would produce pressure variations that would contribute to shot group variance. Hmmmmmmmmm.

CrossHairs · Dec 9, 2009

elsie said:
This might be a bit helpful:

http://www.exteriorballistics.com/ebexplained/4th/56.cfm

elsie

Very helpful. Thanks for the link.

The interesting thing is that the load I am using is right about the minimum mark, and the drop in velocity due to temperature could well be to the point that the actual muzzle rate is now low enough that the round is having a hard time staying on a flat trajectory at all, which is also affecting accuracy.

So, I guess some larger loads and a few trips to the range are in order to test things out.

elsie · Dec 10, 2009

I don't remember if the pistol range at TCGC has a woodstove or not. If it does, you could always crank it up and try keeping your ammo warm that way.

Like you said, you're pretty much at minimum load so anything that reduces the muzzle velocity is probably going to have a more profound affect. I keep my 9mm rounds around the middle of the load chart. I never know if I'm going to be using it in hot or cold so I figured that was the safest bet.

Other things I have heard (these may or may not be urban legend, but it could be worth looking into) that may affect velocity and pressures:

- keeping ammo in the vehicle for extended periods: apparently breaks down the powder granules due to vibration and can cause higher pressure

- small loads in large cases: the powder can end up at the base of the bullet at the farthest point from the primer and can cause incomplete ignition

I've never had a specific issue with any of those, but I keep them in mind.

elsie

CrossHairs · Dec 10, 2009

TCGC does have a fire barrel at the pistol range, I'll take matches next time!

Just doing the math, I think I am going to try out some low mid to mid range loads and see how those pan out (9.0 to 9.2 Acc#7) for the same rounds and see what the net effect is...can't be worse than I was getting, that's for certain.

Yeah, leaving loads in the car does not sound like a good idea...

jib · Dec 10, 2009

(9.0 to 9.2 Acc#7) for the same rounds and see what the net effect is.

Sounds pretty warm ? I'd try a faster powder W-231 and AA#5 come to mind.

<broken link removed>

motoman98 · Dec 10, 2009

I like to work up Elk loads in the winter at or near freezing temperatures. Then in the woods and it's usually in the low 20's or below, I know I have the velocity/trajectory I want. ( I like 3000fps with a 200 gr Nosler in .30 cal.)