Why do shotshells seem to under-perform on a cold day vs. warm day?
John

Shotshell performance is based on powder burn. Chemical reactions are highly dependent on temperature. Propellants, such as nitro powder, are also dependent on pressure for burn rate. The initial cold temperature must be overcome to raise the temperature and pressure sufficintly to achieve normal burn rate. That itty bitty fraction of a second while the powder jump starts itself can sometimes be sensed. A blooper occurs when the powder can't develop enough pressure to get up to normal burn rate before the shot charge moves and increases the combustion chamber volume.

They don't just "Seem To" they actually do. This has been well documented under lab conditions. The Cold Powder doesn't build pressure as fast. Some powders can build excessive pressure under extreme hot conditions. Also some powders are more sensitive to temp changes than others. A fast powder is apt to be more sensitive to "Hot" & a slow powder to "Cold". A slow powder loaded to borderline pressures for it's design characteristics can give total failure in the very cold.

Smile if you like, but for cold weather I use 700X at low pressure, no 4756 or 7625 for me.

Rocketman, as usual, offers a superb explanation.
I use ADI (Australian Defence Industries) powders (many of which are packaged and sold as Hodgdon in the US - for cheaper than we pay here!); temperature sensitivity is something they pride themselves on minimising, borne of research into propellants for military applications under extreme climate variations.
RG.

Balistic Products had cautioned me about the following load that they provided the recipe for.....that it would not do very well in cold weather:

12 ga. 2-3/4 WAA hull
W209 primer
W540 - 34.1 gr.
Balistic Prod. BP12/BPGS + 20 ga. felt in bottom of plastic wad
1-1/4 oz. #5 nickel-plate shot
Tyvek over-card
8-star crimp

Yes, the colder it gets, the less bang (sound) that I get out of it.
John

Another factor in degraded cold weather performance may be the wad becoming stiffer, less flexible and not sealing the load as well.

Keith, you are right. Our club sold really cheap 12 ga wads years ago, and in our Manitoba winters, at -10oC or less these wads turned brittle and seemed to shatter when fired as opposed to Federal and Winchester wads on the same day. Bloopers indeed.
Mike

Question: what is the "standard" temperature that shells are pressure tested?

No smiles from me King; I swore off 7625 about 30yrs ago. Was using a load straight from the then DuPont manual in 12ga with 1¼oz shot @ about 7K psi. We were breaking ice to get a john boat back in the woods in a duck swamp & it totally let me down. I mostly use Green Dot now.

If you get out one of the old WW reloading books you will note they don't have any low pressure loads for hunting. They favor 10,000 psi or more. I am suprised about the 540 comments, we use it for ducks and it was in the teens on many of the mornings, we did use Remington wads?
bill

Some of us have long standing habit of ONLY using cold-weather hunting loads that have at least 9.000 psi at nominal 75F temperatures. We acquired that habit after getting bloopers in cold weather - near freezing or below - with loads of slower burning powders, loads that were just fine at 50F and above.

Lower pressure - lower velocity loads with Blue Dot taught me that lesson one cold day in the marsh. Two more grains of that slow powder and all was well, down to around freezing, at least. My all-time favorate powder for lower pressure, lower velocity loads, IMR SR7625, needs to be loaded to nominal 9K+ psi at 75 F to give reliable perfomance when the ice forms. Green Dot, by contrast, does not produce bloopers so readily when going from 75F to freezing. I use a lot of Green Dot in recent years.

Niklas

Does anyone have experience with PB in low temps? Maybe down to 20 degrees F.

builder,

I used PB heavily for a year or two in the 1970s, in loads having about 9K psi. Don't recall any problems. I switched to IMR SR7625 at similar pressures and had no problems on those few days ice formed along the Texas Gulf Coast. Probably had some of those rare days too when using PB. Don't even recall now for sure why I switched to 7625.

Niklas

Standard atmospheric temperature is around 60 F. Most testing would be near to that temperature.

700X for me also for many years for my waterfowl loads. I used to have the old Mark V Winchester/Western cases occasionally split right down the middle when hunting in cold (<-10F) weather, but not for years. They must have changed their plastic composition slightly.

The one point(I think) that has not been addressed in this thread as well as other threads in the past is the role of the primer. When the temperature get low, the efficiency of the primer deteriorates on two levels. One is the thermal heat sink issue of the primer stuck and surrounded by the metallic shot shell rim. When the temperature gets lower, the lead staphinate (primary explosive)will ignite as well and as quickly as at higher temperature. However, if the primer cup is cold, a substantial amount of the brisance (explosive umph for a lack of better terms)is disipated by the cold copper/brass cowling about the primer cup. I've taken a chunk of dry ice and placed the shot shell base on it for a few moments, enough to get it frosty without cooling down the powder which is insulated by the base wad. Then I stuck it quickly in the gun, so it did not have time to heat up substantially and pulled the trigger. Bloobers or no ignition (WW shells). I haven't done this, but what would be cool is to take the upper part of the shell containing the shot and the powder, wrap it with cloth and ice or dry ice for a bit while keeping the base brass warm and see what happens. Grant it that it isn't too scientific, but this might be an interesting Armbruster like approach to study ignition, shell pressure and fps analysis using a chronometer with different primers and powders.

Iggy

Sorry, I mispoke, the base wad is over the powder, I meant the plastic shell casing, Again, I did this with low brass Winchester 12 out of the box trap loads

Black powder works really excellent in very cold whether I should know. This is written 100 miles north of the Arctic Circle and it is -18C°just this moment.

Welcome to the board, snowman. Iqualiut, Nunavut or Alaska?

Base wad or shell base of single piece hull is under the powder. Interesting point on the primers - thanks!!

Base wad or shell base of single piece hull is under the powder. Interesting point on the primers - thanks!!