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Temp related velocity loss

 
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  #1  
Old 12-05-2005, 07:36 PM
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Temp related velocity loss

Hey guys ,

Winter just set in with a veangeance this very eve. ( 25 degress tonight ) Yes , I know that is not cold ,really , buuut, my pet load is in question as I have not had a chance to chrono it in these conditions to see what the velo diffs are .

Please help as I have a hunt scheduled for the morning and I don't know what to input for the velo in my exbal program. Powder is Re 22 velo 3050 with a 190 smk at temps around 80 to 100.Range is likely to be 350 to 600 yds and I am clueless as far as hard data goes [img]/ubbthreads/images/graemlins/blush.gif[/img]

I know thart I have set my self up for this trouble by using RE22 but hey ! I haven't had time to develop more loads yet( specifically Hodgon powders) and besides , that combo is a tack driver.

Help ! time is short and the deer are moving in response to this front / temp drop. I'm caught with my pants down only because I haven't had enough time to have the summer / winter dope down [img]/ubbthreads/images/graemlins/tongue.gif[/img]

At the short ranges I've mentioned it probably won't be a big deal but I like to put it as close to where I aim as possible [img]/ubbthreads/images/graemlins/smile.gif[/img] and this temp sensitive powder I've built this load on will give me a bit of trouble , I think .

Thanks a heap , Jim
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  #2  
Old 12-06-2005, 12:04 AM
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Re: Temp related velocity loss

Jimm,
As you know, im a Hodgen guy, but back in the dark days when I tried RL22 with my highly specialized and scientific (yeah right) method of temp stabalized ammo testing using ziploc bags of water, ice water, hot water, in my pocket, and in the sun on a hot day, I figured that from typical zero cenditions of about 60-70 degrees, i lost 30fps at ice water temps, and gained 60-70fps on the hottest ones... accounting for the ES of the load. Just a guess, but id say 30fps would be a good guess.
The other option of course would be to keep them in an inside pocket, near to your body so as to keep them closer to body temp, and then load them if you have time, and shoting the cold rounds in the mag if you jump one close.
Good luck! so how many does this one make for the season?
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  #3  
Old 12-06-2005, 05:41 AM
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Re: Temp related velocity loss

In limited experiments,RL-22 drops 2 fps per degree of temperature.
Jimmy
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  #4  
Old 12-06-2005, 10:57 AM
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Re: Temp related velocity loss

[ QUOTE ]
In limited experiments,RL-22 drops 2 fps per degree of temperature.
Jimmy

[/ QUOTE ]

IMO, yes and no. In the rifles I've chrono'd with RL22, I get consistent velocities in the 70-90 degree range. When its 105, the velocities do go up, way up, along with the pressure. I will chrono my 190 VLDs in January when its chilly to see how much I lose.

Out of curiosity, I wonder what effect load density has on the velocity difference. With three different seating depths I tested in late August early September, the bullet 0.005" into the lands was the fastest and most accurate, a bullet loaded 0.005" off the lands was the slowest and a bullet loaded roughly 0.050" off the lands to fit in the mag was just under the bullet into the lands. I don't care to get into the physics of how and whys, but I am getting the same results in my 300 RSAUM with SMKs and heavier Berger VLDs. I am shooting 175 SMKs at 2875 fps with the bullet off the lands and 185 gr Berger VLDs about 0.010" into the lands at up to 2971 before I got crater'd primers and sticky extractions. Everything else was the same. I don't plan to do anymore experiements like that changing components and all, but I may have found a greener pasture. Time and more groups will tell.
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  #5  
Old 12-06-2005, 07:41 PM
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Re: Temp related velocity loss

Bullet warmer

I am using RL22 in my 7Wby and it was developed in 75-80 temperature. As Sewhat says at 100 degrees I had to hammer the case out of the chamber with a cleaning rod. Last week it was about 40 degrees when I was hunting, I keep rounds in my tee shirt pocket for long range and I got bored and dialed a rock at 796 yds and pulled out a warm round and quickly fired. I did it again because it was so much fun. Both rounds were exactly on.

Today was about 25 degrees and I just got home from hunting. What I did for today was take a brown cotton work glove (you know the kind that cost $1.99 and lasts about five minutes) and poked some holes in the wrist cuff and ran a boot lace through the holes to make a necklace. I put one cartridge in each finger and two in the thumb of the glove and dangle in inside my shirt next to my skin.

For close range I have a cartridge in the chamber and some in my pants pocket. Just my guess but the ones in the pants pocket are at a temperature of about 55 degrees, the one in the chamber at 25 degrees and the ones in the glove next to my skin are about 85 degrees. I worked on this temperature issue a bit today. So I think those estimates are good enough that you should not believe that bullets in your pants pocket area "warm". Once you put a warm round in the chamber you must fire fairly quickly or it will cool off. I will post a picture of my bullet warmer when I get the roll of film developed. To avoid patent infringement I suggest you can use a sock.

I had a buck chasing a doe at about 840 yds in a scrub brush field next to the river but he was intent one chasing and was in and out of the brush and never got still and finally the light gave out and I had to give it up.

There were some resident Canadian geese down on the river at ranges from 700 yds to 1050 yds and I was so badly tempted I could hardly resist. Seems like all of the fun stuff is illegal.

Good luck tomorrow . I hope to get back out on Thursday or Saturday.
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  #6  
Old 12-06-2005, 08:00 PM
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Re: Temp related velocity loss

Jimm, The Hodgdon site shows a 75fps change in R22, between 0 and 125degrees. So a 30-50 fps guess should be in the ball park. Good luck with your hunt.
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  #7  
Old 12-07-2005, 02:44 AM
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Join Date: Feb 2003
Location: Pueblo, CO
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Re: Temp related velocity loss

Jeez Bob-- i've got it on pretty good account that anything i keep in my pants gets pretty hot-- at least warmer than 55 degrees, i hope.
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