Compensating for temp sensitivity

1stmar · July 30, 2013, 05:59 AM

I am using imr4064 and have found it to be sensitive to temp variations. Shooting in the north east I get great variations in ambient temperatures. Wondering if anyone has found a way to stabilize the temp effectively , ie range bag with ice pack?

Dan Newberry · July 30, 2013, 09:28 AM

With an OCW load (optimal charge weight) temp variations will be kept to a minimum. Google OCW load development and you'll find my site, with explanation.

IMR 4064 isn't as bad for temp swings as many other powders. It could be worse...

Varget is a good option for better temperature stability in the 4064 burn range.

Dan

1stmar · July 30, 2013, 05:38 PM

Thanks Dan I am familiar with your website and ocw. Very much appreciated. I like varget but have only been able to get 4064 so I bought 6 lbs.

jmr40 · July 30, 2013, 08:22 PM

If you can find it Varget, RL15 or H4895 are less sensitive to temperature. expect about 1 fps difference for 1 degree temperature change. The others listed will be around 1/3 to 1/4 that. I try to use those powders for that reason, but 4064 works pretty good too, and temperature sensitivity is probably something I worry about more than I should.

If you work up a load when temps are around 50 degrees you should see about 50 fps less at 0 degrees, and about 50 fps faster at 100 degrees. Personally I'm more concerned about getting an overpressure load in hot weather. I'd think it would be easier to compensate for a little slower bullet in cold temps if I knew what to expect. 50, even 100 fps slower doesn't really become a huge factor until you get to some pretty long ranges.

July 30, 2013, 05:59 AM	#1
1stmar Senior Member Join Date: March 21, 2012 Location: Connecticut Posts: 2,378	Compensating for temp sensitivity I am using imr4064 and have found it to be sensitive to temp variations. Shooting in the north east I get great variations in ambient temperatures. Wondering if anyone has found a way to stabilize the temp effectively , ie range bag with ice pack?

July 30, 2013, 09:28 AM	#2
Dan Newberry Senior Member Join Date: October 3, 2012 Location: Wytheville, VA Posts: 216	With an OCW load (optimal charge weight) temp variations will be kept to a minimum. Google OCW load development and you'll find my site, with explanation. IMR 4064 isn't as bad for temp swings as many other powders. It could be worse... Varget is a good option for better temperature stability in the 4064 burn range. Dan

July 30, 2013, 05:38 PM	#3
1stmar Senior Member Join Date: March 21, 2012 Location: Connecticut Posts: 2,378	Thanks Dan I am familiar with your website and ocw. Very much appreciated. I like varget but have only been able to get 4064 so I bought 6 lbs.

July 30, 2013, 08:22 PM	#4
jmr40 Senior Member Join Date: June 15, 2008 Location: Georgia Posts: 10,830	If you can find it Varget, RL15 or H4895 are less sensitive to temperature. expect about 1 fps difference for 1 degree temperature change. The others listed will be around 1/3 to 1/4 that. I try to use those powders for that reason, but 4064 works pretty good too, and temperature sensitivity is probably something I worry about more than I should. If you work up a load when temps are around 50 degrees you should see about 50 fps less at 0 degrees, and about 50 fps faster at 100 degrees. Personally I'm more concerned about getting an overpressure load in hot weather. I'd think it would be easier to compensate for a little slower bullet in cold temps if I knew what to expect. 50, even 100 fps slower doesn't really become a huge factor until you get to some pretty long ranges.