SmallCaliberCentral

Hello again . Starting to test & load my 204 for a PD hunt in S. Dakota in June . Plan to be using IMR4895 under 32gr. vmax & CCI BR4 primers, to start with . Here in Pa. temp is 40 to 60 deg. this time of year & I expect much warmer if not down right hot in S. Dakota in June. Is IMR4895 going to build undo presure in hot weather if i need to load near max? I have 8lbs of this powder.(I use it for 222 rem with good results but not near max.) If I need to buy a different powder I can but would like to save the $$$.

You should look up the powder with the manufacturer's website to see what the temp tolerances run.

Normally, I will prep all my brass and hold off working up exact loads until right before I go due to the potential effects of the temp change. It doesn't take that much time to charge and seat bullets

I use powders that are considered "extreme" for the temp changes and have found in the past that, while there are no real pressure problems, the accuracy will change due to temperature and elevations...Or maybe I just shoot a little differently in hot weather...

Many folks "claim" the "EXTREME" powder designation is just a bunch of maketing hype and have supposedly tested several powders of the "EXTREME" variety and powders of the "NON-EXTREME" variety and found that there wasn't a lot of difference.

As for me, I will continue to use the Hodgdon Extreme powders for up here in North DaColder where the temperature can be anywhere from 32º to 110º when I am working up loads and then be anywhere from -32º up to 110º when I am out shooting those loads in the field. I just "FEEL" better about using the Extreme powders. I have no documentation to prove the theory that they are less sensitive to temperature extremes than other powders, but I like that "FEEL GOOD" feeling anyway.

I just don't believe in loading up super hot loads in temperatures down in the 30 to 60 degree temperatures and then using them out in a prairie dog town when temps run 80 to 110 degrees. That just isn't using good common sense. It would certainly be better if you could work your loads up in the same or similar temperatures as you are going to experience when you use those rounds in the field. That's not always practical, so keep those loads in the safe zone in case the temperatures do get extremely hot or you happen to forget a round in a hot chamber and cook it a wee bit!!!

I cannot say anything about the IMR powders, but looking at a Hodgdon manual, H4895 is an extreme powder, and so is Benchmark. Personally, I load Benchmark in my 204, with very good results. When I was working up some loads this past summer and into fall, the weather was pretty warm, and at times I was testing loads up to just under max. I learned a little trick from a shooting buddy. He told me to keep my ammo in an ice chest, to keep below some temp extremes and try to keep over pressure problems from being a problem. I never had any signs of over pressure during testing. He always keeps his loads for his 22-250 in a cold ice chest when shooting belding squirrels. We get some real swings in temps around here, anywheres from the mid 30's all the way up to the mid 90's at times. Maybe this will help you.

Here's an article from Sierra that talks about cartridge temperature effects. I know its not exactly about what you are asking in that its not about pressure differences, but it does talk about cartridge temp's effect on velocity.

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

This article is from sierra's online manual found out

http://www.exteriorballistics.com/ebexplained/index.cfm

Here is what I know, which ain't much. I have loaded my Savage 22-250 for years this way.
In colder weather I load H380 gives my 3/8" groups @ 100 & 200 yds. But when the temp rises,
I have to go to Varget. My H380 loads will go all over the paper. Varget which is not as accurate
for me, 1/4" @ 100yds and 1/2" @ 200 yds. is at least constant in the warmer temps.