Temp effect on reload velocity

[rep308]

I froze my butt off yesterday to chrony a load:

200gn SWC, 45 ACP
5.3 gn of Win 231
1.255 OAL
WLP, Starline Brass

My old load results showed this at 840 at 75 deg F, and here is a reference to back up my results:
http://www.reloadersnest.com/detail_handgun.asp?CaliberID=17&BulletWeight=200&LoadID=437

It was 20 deg F and the ammo was in the trunk of my car for a couple of hours so it too was darn cold. The results were 30 to 40 fps, lower than I expected averaging 800 fps.

Does this make sense that a 50-60 degree temp would result in a 30 to 40 fps drop? My intent was to make IPSC major at 1650.

 

[Dick]

This discussion (http://www.exteriorballistics.com/ebexplained/4th/56.cfm), which I believe may be excerpted from the Sierra Bullets reloading manual - or at least appears to be put out by Sierra, would seem to indicate that your results are typical.

 

[rep308]

An informed response with references, within half an hour is why I love this place. I'm going to bump up my load a .1 of a gn that should get me 850 fps at 70 deg F with a power factor of 1700 and not shoot if it is below freezing!

 

[Supermoto]

Different powders react differently to temp. Alway add a buffer, 168-170pf is were you want to be, 165pf is a great way to go minor at a big match