I wonder what MV you'd record if you'd freeze both the rifle and ammo, and then record a single shot - for comparison purposes to only the frozen ammo. You'd need a chest freezer. I think the shell would warm up pretty quickly when placed in a much warmer chamber - depending on how long the shells were out of the freezer and/or in your chamber before you fired them.
RL33 Temperature Regression Thread
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I wonder what MV you'd record if you'd freeze both the rifle and ammo, and then record a single shot - for comparison purposes to only the frozen ammo. You'd need a chest freezer. I think the shell would warm up pretty quickly when placed in a much warmer chamber - depending on how long the shells were out of the freezer and/or in your chamber before you fired them.
barnesuser28
Well-Known Member
The rounds were in the freezer over night, i put them in a cooler (with ice packs) and went to the range, i brought the heat gun and a powder pan, and disassembled a round and recorded the powder temp, i tried to fire the rounds within 10 seconds of them being in the chamber. I think the brass changed temp fast but it would take a while for the powder to change temp. I think i am just going to log muzzle velocities throughout the summer and fall and see what my average change is, i will share once i have collected my data.
Riley
Riley
elkaholic
Well-Known Member
Good idea!......Rich
Broz
Well-Known Member
Guys I have been doing a little testing and have not read this thread fully so hope this is not redundant. But I have been seeing bigger changes in MV when both the rifle and ammo are at the same temps. Some results might even surprise you. Like a gain in velocity at colder temps.
For what its worth I feel if you want to record data for use in a ballistic app to calculate a shooting solution, the rifle and ammo need to be at the same temp. And the first shot data is the most valuable.
Jeff
For what its worth I feel if you want to record data for use in a ballistic app to calculate a shooting solution, the rifle and ammo need to be at the same temp. And the first shot data is the most valuable.
Jeff
Great thread on RL-33. I'm tagging in to keep up on it. I currently have 8 lbs of 33 and a few boxes of Berger 250 grain Elite Hunters... but still waiting for my 338 RUM to be built... not going to show up until September, but I will definitely post up my results when I finally get the setup shooting.
I concur. And that's what I do. I freeze the rifle and ammo in the chest freezer and then shoot the round within 30 seconds of pulling it out of the freezer, in order to prevent condensation and ice buildup in the bore if I'm conducting the MV test during warmer months. This allows me to conduct at least one cold temp test of MV even during warmer summer months, prior to hunting season.
After all, the rifle and ammo in the field at the time of success (or something less), are both at the same temperature for the first shot. I haven't conducted the multitude of tests that would be required to demonstrate clear trends or conclusions. Too much work, and I really only need the data from my specific rifle and ammo combination.
Thanks Jeff for sharing your findings to date. If we all share, maybe collectively, perhaps we'll generate enough data to reach a reliable conclusion. Or maybe not... There are a lot of variables in play.
benchracer
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I read something to that effect on accurateshooter.com quite awhile ago. I think it was written by German Salazar, but I don't remember for sure. I do think it would be useful to track primer type in the loads being analyzed. Other than that, I am not really sure how one would go about testing primer temp sensitivity.
Primer temp sensitivity seems to get left out of most temp sensitivity discussions and it seems to me that it could be just as important as powder temp sensitivity.
Broz
Well-Known Member
You are welcome. The powder / temp variation mode of some Ballistic apps has always intrigued me. How ever it was soon learned that if not used very accurately it would cause more harm than good. Thus my conclusion, at this point at least, is that the powder with the least temp swing will always be best as we are working inside a smaller error margin. But, it is also becoming evident that barrel contraction or expansion from ambient temps is as important on that first shot as actually how the burn of the powder reacts to temps.
Maybe the powder / Temp variation corrections would be better off used to correct for tighter contracted barrel / bore dia. and the effects this has on velocity. Or in the end a combination of both.
Either way more testing is needed and my most trusted data are the ones I record in the coldest or warmest ambient temps when the rifle and ammo has had adequate time to acclimate. It just takes time and good notes.
Jeff
azsugarbear
Well-Known Member
Ditto. Just got my 338 Lapua Imp. back from the smith. I got 9 lbs. of Retumbo and 2 lbs. of RL33. Very interested in velocity deviations in the hotter months of summer.
dkhunt14
Well-Known Member
I think you got to be careful cooling down and freezing ammo. When taken out they immediately begin to sweat inside and out. Moisture in powder changes the burn rate. moisture in your chamber causes the casing not to grip the chamber when fired and raises bolt thrust. Too much moisture after firing a couple of shots takes up chamber space and raises pressure also. When I tested the R33 in a Lapua Imp while hunting in the morning it was cold and we shot at a rock at 1650 and late afternoon it was up to 40 degrees and the point of impact was really close so I don't think it is real temp sensitive. Matt
Cartridges are sealed from ambient air outside of the cartridge. They can't sweat much inside the brass casing because there's a very limited volume of air (and moisture) inside the casing. Which is why cartridges remain viable for many years in spite of how many times they're placed in freezing temperatures and then back into heated homes.
Moisture does condense on any cold surface placed in warmer air, because there's an unlimited source of moisture in warmer ambient air. Which is why moisture condenses on the cold toilet bowl, or cold items removed from the fridge or freezer into a warmer atmosphere. This is also why I shoot and record MV within 30 seconds after removing my frozen rifle and ammo from the chest freezer, on days when the outdoor temps are much warmer than those in my chest freezer. I'm not shooting at a target. Only shooting over the chronograph skyscreens. The chronograph is set up 30 feet from the outdoor chest freezer. Put on hearing protection, pull the rifle out of the freezer, turn around and shoot.
dkhunt14
Well-Known Member
When you come in from outdoors in the cold your glasses immediately sweat. Ammo does the same. Ask the guy that tried it and sheared his bolt lugs. Moisture doesn't let the brass grip the chamber walls and goes into bolt thrust. I just thought you should know for safety reasons. He only lost three fingers and was lifeflighted to the hospital to get the bolt removed from his shoulder. Matt
Broz
Well-Known Member
Any moisture on a chamber wall or outside of a case will increase pressure. I have seen it and I watch it very closely now. Just one of the many reasons I choose to do and temp / velocity testing at ambient temps with the rifle and ammo acclimated to the temp out doors.
Jeff
Jeff
