Marshall Stanton
01-11-2001, 07:48 AM
I thought that a thread concerning load development and ambient temperature might be in order now.
Being that it is now mid-January, and most of us who shoot are somewhat cooped up, now is the time that much load development takes place amongst our ranks. *This is a natural way to beat the cabin fever we seem to endure each winter, especially if you live in the snow belt.
However, this tendency to develop a pet load during the winter months can and does have potential dangers! *Although we don't hear much about it any more from gun writers, the hazards still exist. *What am I talking about?
The hazards of working up a maximum load in any cartridge during winter months when the ambient temperature can be a full 50-60 degrees below temperatures encountered later in the year when the same ammo can and will be used! *A load that is worked up to absolute max during the winter, and all range testing and chronographing is done when the temperatures are near or below freezing, can and most likely be into the <span style='color:red'>red zone</span> once temperatures become comfortable for shirt sleeves!
I once worked up an absolute max load in my Marlin .375 Winchester using a BTB .377"-250g LFNGC bullet and a mighty stiff load of AA 1680, and fire-formed .30-30 brass. *That load, worked up one very cold week in December yielded 2360 fps with only slightly pushing the pressure envelope! *I was ectatic! *It was superbly accurate and repeated loading and firing of the same case revealed good case life. *I was in fat city!
Now, for the rest of the story. *Our fall black bear season began on a very hot September 15th that year. *Using my wonder load in the little Marlin .375 Winchester, I was loaded for bear. * I had an opportunity to take a coyote about noon that day, the temperature, while not having a thermometer handy, must have been near 80 degrees, I had been comfortable in a T shirt since before sun-up that day.
When I popped (at) the coyote, my world momentarily went black! *My shoulder cried out, and my right hand was wrenched open as the lever on the rifle sprung open! *I staggered backwards, and after recovering from the shock of surprise, assessed the situation. *I had missed the coyote from about fifty yards... I don't have a clue where that bullet went, but it must have left in the form of smoke and lead vapor! *The cartridge case remained stuck until I got home, removed the lever and the bolt from the rifle and drove it out from the muzzle with a brass rod! *The case had a huge hole where a primer once had been!
I double checked the loads left in that lot of ammo, it had all been loaded in the same session, with the same lot of brass, the same powder measure with an unchanged setting, primers out of the same box and bullets from the same lot. * After pulling the bullets from every fifth round and checking the powder charges, all was as recorded on the loading label.
Now, for the stupid part... I figured that something must have been wrong with the one load I fired. *It was the next day with early afternoon temperatures near 90 degrees. *I tested one more round out of the Marlin... again, pain, sprung action and a bullet with unknown destination. *Again, back to the shop to pull lever and bolt and drive out the case with a brass rod... with the same results as the round fired the previous day.
Although this is absolutely the most extreme case of this I have experienced, it was a sobering event, and it prompted me to make detailed notes not only of pressures but temperatures during those testing periods. (If you will notice our Printable Resources Loading Notes and Targets all have spaces for temperature)
Yes, we now have powders that minimize this pressure swing due to temperatures. *The new Hodgdon Xtreme powder series does minimize, but not eliminate this phenomenon. *I have noted over the years since my described experience significant changes not only in velocity but pressures as temperatures have fluctuated.
Back in the heydays of Ivory Hunting in Africa, the Kynoch ammo loaded for use specifically on the Dark Continent was loaded to pressure levels such that with the extreme heat of African exposure, pressures would not spike beyond the designated accepted standards.
We too can learn a lesson here. * Enjoy the winter load development sessions... but <span style='color:blue'>PLEASE</span> don't seek that magic MAX load with MAX pressures and MAX velocities! *Otherwise you might find yourself <span style='color:red'>MAXED OUT!</span>
I'm somewhat concerned about some of the loading data that people are sharing that has been recently developed, as although they may very well be within the realm of reasonable pressures now, in the winter conditions they have tested them, I suspect that some very serious pressure problems are on the horizon as ambient temperatures rise.
Use caution, enjoy the winter months, and keep GOOD records.
God bless,
Marshall
Being that it is now mid-January, and most of us who shoot are somewhat cooped up, now is the time that much load development takes place amongst our ranks. *This is a natural way to beat the cabin fever we seem to endure each winter, especially if you live in the snow belt.
However, this tendency to develop a pet load during the winter months can and does have potential dangers! *Although we don't hear much about it any more from gun writers, the hazards still exist. *What am I talking about?
The hazards of working up a maximum load in any cartridge during winter months when the ambient temperature can be a full 50-60 degrees below temperatures encountered later in the year when the same ammo can and will be used! *A load that is worked up to absolute max during the winter, and all range testing and chronographing is done when the temperatures are near or below freezing, can and most likely be into the <span style='color:red'>red zone</span> once temperatures become comfortable for shirt sleeves!
I once worked up an absolute max load in my Marlin .375 Winchester using a BTB .377"-250g LFNGC bullet and a mighty stiff load of AA 1680, and fire-formed .30-30 brass. *That load, worked up one very cold week in December yielded 2360 fps with only slightly pushing the pressure envelope! *I was ectatic! *It was superbly accurate and repeated loading and firing of the same case revealed good case life. *I was in fat city!
Now, for the rest of the story. *Our fall black bear season began on a very hot September 15th that year. *Using my wonder load in the little Marlin .375 Winchester, I was loaded for bear. * I had an opportunity to take a coyote about noon that day, the temperature, while not having a thermometer handy, must have been near 80 degrees, I had been comfortable in a T shirt since before sun-up that day.
When I popped (at) the coyote, my world momentarily went black! *My shoulder cried out, and my right hand was wrenched open as the lever on the rifle sprung open! *I staggered backwards, and after recovering from the shock of surprise, assessed the situation. *I had missed the coyote from about fifty yards... I don't have a clue where that bullet went, but it must have left in the form of smoke and lead vapor! *The cartridge case remained stuck until I got home, removed the lever and the bolt from the rifle and drove it out from the muzzle with a brass rod! *The case had a huge hole where a primer once had been!
I double checked the loads left in that lot of ammo, it had all been loaded in the same session, with the same lot of brass, the same powder measure with an unchanged setting, primers out of the same box and bullets from the same lot. * After pulling the bullets from every fifth round and checking the powder charges, all was as recorded on the loading label.
Now, for the stupid part... I figured that something must have been wrong with the one load I fired. *It was the next day with early afternoon temperatures near 90 degrees. *I tested one more round out of the Marlin... again, pain, sprung action and a bullet with unknown destination. *Again, back to the shop to pull lever and bolt and drive out the case with a brass rod... with the same results as the round fired the previous day.
Although this is absolutely the most extreme case of this I have experienced, it was a sobering event, and it prompted me to make detailed notes not only of pressures but temperatures during those testing periods. (If you will notice our Printable Resources Loading Notes and Targets all have spaces for temperature)
Yes, we now have powders that minimize this pressure swing due to temperatures. *The new Hodgdon Xtreme powder series does minimize, but not eliminate this phenomenon. *I have noted over the years since my described experience significant changes not only in velocity but pressures as temperatures have fluctuated.
Back in the heydays of Ivory Hunting in Africa, the Kynoch ammo loaded for use specifically on the Dark Continent was loaded to pressure levels such that with the extreme heat of African exposure, pressures would not spike beyond the designated accepted standards.
We too can learn a lesson here. * Enjoy the winter load development sessions... but <span style='color:blue'>PLEASE</span> don't seek that magic MAX load with MAX pressures and MAX velocities! *Otherwise you might find yourself <span style='color:red'>MAXED OUT!</span>
I'm somewhat concerned about some of the loading data that people are sharing that has been recently developed, as although they may very well be within the realm of reasonable pressures now, in the winter conditions they have tested them, I suspect that some very serious pressure problems are on the horizon as ambient temperatures rise.
Use caution, enjoy the winter months, and keep GOOD records.
God bless,
Marshall