Cold bad for rifle cartridges?

[Ben Long]

During the Polar Vortex (formerly known as a 'cool spell' here in Montana) I left a box of hand-loaded 308 cartridges in my pickup truck for about a week of subzero temperatures. Practically speaking, would this impact the reliability or accuracy of these loads? Powder is Hodgeson CFE .223. I am not a freak about getting MOA accuracy, but my rifle is finicky.

 

[MKotur325]

Short answer: No, your ammo should perform just fine.

 

[Gr8bawana]

I think ammo is good forever unless moisture somehow gets inside.

 

[MThuntr]

Shouldn't be an issue...if so I'm in deep trouble.

I'd be more concerned about taking cartridges from -20 outside to 72 degrees inside possibly causing moisture.

 

[danr55]

I'm going to say it depends.. on how close your handloads are to max and what powder you used to load them. Some powders are extremely temperature sensative.. Some are not. Any cartridge and be sensative if it is loaded to max or over.

 

[schmalts]

I'm going to say it depends.. on how close your handloads are to max and what powder you used to load them. Some powders are extremely temperature sensative.. Some are not. Any cartridge and be sensative if it is loaded to max or over.

I think you are talking about temp sensitive at the time of being shot and Ben is talking after they were put back in a warmer climate. It is my understanding that when some powder is referred as temp sensitive it means what the burn rate change is at that given temp, and not the effect temp will have on the burn rate permanently

 

[Ben Lamb]

You should just send that Kimber & the ammo to me. I'll make sure they're safe.

 

[bjtc_brian]

Depends on when you're talking about. CFE is a temp sensitive powder. I avoid all temp sensitive powders for the reason that I use rifles in all types of weather, and have seen the affects of temps causing pressure issues when not previously seen in cooler temps. The speeds of some of these powders is intriguing, but not worth the risk, imo. My .02 cents.

 

[MKotur325]

Ok... Let me clarify a bit. I see no reason that ammo stored in cold temps for a week will be affected by cold storage.

Velocity change based on temperature is based in physics (thermodynamics and kenetics). The colder the powder at the time of the shot, the more of the energy stored in the powder is used elevating the temperature inside the case to the flash point of the powder. This effectively reduces the pressure; and thusly the velocity.

If you shoot those loads at -20, you can expect a noticeable velocity drop. Sphereical powders in some cartridges can see 1.5-3fps/degree of velocity change. Meaning if you know you your velocity at 70 degrees, you MAY see a drop of as much as 135-270fps at -20. Not all powders are this sensative, but ball powders tend to be a bit more susceptible to velocity change based on temperature shifts than extruded powders. Some powders are designed to be insensitive to temperature changes. I'm not aware of any spherical powders designed this way. If you are interested in any powders that would be more temperature stable, for a .308, Varget, H4895 IMR 4166 and IMR 8208XBR would all be good starting points. Those 4 powders are all specifically designed to maintain consistent velocity across all temperature ranges.

 

[Ben Long]

Well, come to think of it I was hunting in subzero temperatures as well. The round worked just fine at -5 but the shot was only 50 yards... Interesting thread.

 

[Mthuntinfool]

As long as they dont go through extreme temp swings( -20 to next to the woodstove) they shouldnt build condensation inside the case, which would affect performance. I leave my ammo in the truck during hunting season for that exact reason, and I have never had a problem

 

[danr55]

Spend some time at a bench rest match. Look and see how many shooters keep their ammo on ice until they are ready to shoot it.. Nuff said.

 

[jryoung]

Spend some time at a bench rest match. Look and see how many shooters keep their ammo on ice until they are ready to shoot it.. Nuff said.

Never been to a benchrest match, but that seems like a consistency issue, not a "cold" issue. Meaning, by putting it on ice they can control the temp within a range as opposed to shooting at a match in the spring at 40 degrees and in the summer at 80.

 

[Rooster52]

Shouldn't be an issue...if so I'm in deep trouble.

I'd be more concerned about taking cartridges from -20 outside to 72 degrees inside possibly causing moisture.

What he said.

 

[mtmuley]

I've had ammo that I carried and left in the truck in subzero, then brought in the house. Sometimes repeatedly during a hunting season. Or I've left it in a vehicle all season through warm and cold. All handloads in various chamberings with various powders, some considered "temp sensitive". I've seen zero issues as far as reliability or function. No pressure issues or anything. Some ammo was even used the following year. mtmuley