Interesting Observation with Temperature and AA No.7 / 9MM

[Echocrewchief]

Thought I would pass along an experience relating to outside air temperature. Likely old news to most folks here...

I had purchased some Accurate No.7 and wanted to try out some 9MM rounds with it.

Missouri Bullet 124 grain Lead Smallball
5.0 grains of A No. 7
COL 1.050"
Outdoor air temp: 31 degrees
Weapon: XDm 3.8" barrel

Round was extremely accurate, but there were several failures to feed. Recoil was very light. Tried a few rounds in a G26 with the same results. My nephew's Ruger LC9 was able to fire them without issue. We didn't weigh the slides, but I'll assume the Ruger slide is lighter.

Same recipe but the outdoor air temperature this time was 55 degrees and the XDm was able to cycle the same rounds without issue. Recoil was still light, the round was accurate, but a lot of smoke.

Made up 30 additional rounds at 5.2 gr., 5.3 gr. and 5.4 gr. - all fired fine and the smoke seemed to be a lot less.

I've read some other posts about temperature sensitive powders - is there a list of powders that are very sensitive - like the burn rate chart?

 

[Walkalong]

Your charge is too low. Toss in cold temps on top of that, and you get weak rounds.

 

[gamestalker]

Just a quick glance at the data says you are significantly below published start charge.

GS

 

[Steve C]

You will get lower velocities by some amount from any powder under cold conditions as cold air is heavier as well as reducing the burn rate somewhat. A truly temperature sensitive powder will have erratic pressures and may even have higher pressure when cold. Blue Dot is an example of a temperature sensitive powder often used in handgun loads that performs erratically in the cold but does fine in hot weather.

That being said, as others have mentioned you are below start levels for AA7 using a 125gr Lead bullet. Go on line and download the Accurate manual No 5. and save it for future reference. You will find they list the 9mm load for a 125gr lead bullet as 5.7 to 6.5 with AA7.