Is accuracy negatively impacted when developing loads over the winter months and then expected to perform in the other seasons? Powders used are only from the Hodgon Extreme line, no ball powders. For example if I developed an accurate load in January @ -10C for my 300 WinMag with H4831SC 200 Gn Sierra MK could I expect the chamber pressures, extreme spread, group size etc to be similar throughout the other seasons?
Winter Load Development
- Thread starter MidnightRun
- Start date
- Location
- Somewhere on the Hudson Bay Coast
Depends how you look at it. If you work up a maximum load that you test at -35, at +35 the pressure will be much higher. At the very least you can expect a change of POI, and if your cold weather loads are maximum, those loads could cause sticky bolts in the summer.
So if I delevloped a repeatable 1/2 moa load with H4831sc or H4350 or H1000 at -10C in January, other than +-predictible POI shift due to atmospheric variables could I reasonably expect to still have a 1/2 to 1 moa load at +20C in June? Given that I am at max powder weight and well on the safe side of any pressure signs at either temperature extreme.
- Location
- Somewhere on the Hudson Bay Coast
I doubt if -10 is going to make a huge difference between your summer time and winter loads. I recently did some load development for the .375 Ruger and shot at -32. Using my .375 Ultra as a control, I seemed to have 40 fps below what I would expect to see in warm weather. I load with H-4350 and the velocities when chronograph in warm weather are very uniform. This would seem be be the case with the .375 Ruger as well as velocities seemed to be about 40 fps below what was projected from loading data, but could also be effected by the short barrel.
Clearly pressure has an effect on accuracy, so you will have to recheck your loads in the warm weather to be sure.
Clearly pressure has an effect on accuracy, so you will have to recheck your loads in the warm weather to be sure.
Now if you read my first post
take a look at this link http://www.hodgdon.com/smokeless/extreme/page2.php#top
I have developed loads that shot tight groups in summer that opened up in colder weather.Those particular loads were also very sensitive to powder charge.In other words if the accuracy changed significantly by adding or subtracting a grain of powder,it usually changed significantly with a big change in temperature.The loads that were stable when adding or subtracting a grain of powder,also seemed to be the most stable in changing temperatures.
