Lefty7mmstw
Well-Known Member
yup...my bottle says made in Switzerland on it....
Reloder 33
- Thread starter royinidaho
- Start date
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Did some temperature testing today. Previous shooting and chronographing was done in 85-90 degrees with this rifle. It is a 7mm/375 Ruger shooting a 180 match target hybrid with 84 grains of RL-33.
Velocity at 85-90 was 3075 fps
Today's test: put five rounds in a baggie and left it in the chest freezer along with an AC thermometer. It was 20 degrees. Placed baggie into soft cased cooler with a frozen gatoraide bottle under the baggie with another on top. Used my CO2 system to get the barrel very cold (unknown value but at least it wasn't ambient) then shot one shot of ammo that registered approx. 40 degrees when taken from the cooler bag with thermometer touching ammo. Continued to shoot a round pulled from the cooler bag and cooled barrel after each shot for five shots. Average velocity was 3035 fps.
The temperature spread from hot to cold is approx. 47.5 degrees. Velocity drop is 40 fps. The powder looses .84 fps per degree of temperature drop.
I admit the test could be better. I need to get an infrared temperature gun or temperature probe.
The load still shot a nice .300"ish cluster at 100 yds.
Perhaps as the weather gets colder others will have actual ambient temperature comparisons.
Velocity at 85-90 was 3075 fps
Today's test: put five rounds in a baggie and left it in the chest freezer along with an AC thermometer. It was 20 degrees. Placed baggie into soft cased cooler with a frozen gatoraide bottle under the baggie with another on top. Used my CO2 system to get the barrel very cold (unknown value but at least it wasn't ambient) then shot one shot of ammo that registered approx. 40 degrees when taken from the cooler bag with thermometer touching ammo. Continued to shoot a round pulled from the cooler bag and cooled barrel after each shot for five shots. Average velocity was 3035 fps.
The temperature spread from hot to cold is approx. 47.5 degrees. Velocity drop is 40 fps. The powder looses .84 fps per degree of temperature drop.
I admit the test could be better. I need to get an infrared temperature gun or temperature probe.
The load still shot a nice .300"ish cluster at 100 yds.
Perhaps as the weather gets colder others will have actual ambient temperature comparisons.
MontanaRifleman
Well-Known Member
Thanks for the report. I'll try to do some testing as well in the coming weeks.
Anyone know what the difference in velocity performance is for Retumbo?
Lefty7mmstw
Well-Known Member
Much better test than the ice the ammo and leave everything else hot crew
Montana and I can get some darn cold temps in our states. I'll have to rustle up my oehler (or buy one) so I've got a reliable chrono to play with; I don't trust my CED very much lately. The few shots I've gotten over chrono's with the 225hdy in my 300 rum in differing temps show little difference but I've not rapped off 5 at 100f and 5 at 0f yet for a reference so I'll say I'm not sure.
There sure are a ton of variables. I just ordered an infra red gun to KNOW the temperatures of the brass and barrel. The chrono lighting can be another variable as the precise distance to chrono can vary.
This stuff can drive a guy nuts.
Ideally I'd like to chrono AND shoot at our 500 M ram which is 45 miles away. Needless to say I don't go there too often. Hope to get there in early Nov when it cools off around here.
Hope others can get some data out there soon
This stuff can drive a guy nuts.
Ideally I'd like to chrono AND shoot at our 500 M ram which is 45 miles away. Needless to say I don't go there too often. Hope to get there in early Nov when it cools off around here.
Hope others can get some data out there soon
MontanaRifleman
Well-Known Member
I'll be using an accustic SuperChrono and a Magnetospeed when I get it. I had soem accuaracy issues with the SuperChrono but that might have been due to how I set it up. I'm thinking I would like to get some data on RL17 and Retumbo as well.
