Forums
New posts
Search forums
What's new
Articles
Latest reviews
Author list
Classifieds
Log in
Register
What's new
Search
Search
Search titles and first posts only
Search titles only
By:
New posts
Search forums
Menu
Log in
Register
Install the app
Install
Forums
Rifles, Reloading, Optics, Equipment
Reloading
Retumbo & Temperature
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Reply to thread
Message
<blockquote data-quote="Pdvdh" data-source="post: 516193" data-attributes="member: 4191"><p>I just opened my ballistics software program to see if I had remembered correctly or not. Here's some data from my records - which is more accurate than my memory. The temperature versus muzzle velocity modeling for my 7mm Rem Mag with 74.6 grains Retumbo and the Berger 168 VLD:</p><p>77F = 3058fps</p><p>68F = 3054fps</p><p>59F = 3044fps</p><p>32F = 3039fps</p><p>14F = 3045fps</p><p>05F = 3044fps</p><p>Pretty temperature stable from 5F to 59F.</p><p></p><p>Here's the temperature versus MV data from my .280 RCBS 30-Degree Improved, loading 62.5 grains H1000, with the 162 grain Amax:</p><p></p><p>68F 2920fps</p><p>59F 2937fps</p><p>41F 2948fps</p><p>23F 2948fps</p><p>Approximately 28fps <strong>increase</strong> in MV as temperatures dropped from 68F to 41F with H1000.</p><p></p><p>With the .280 RCBS Improved, H1000, and the 168 grain Berger VLD, I see about a 5fps increase in MV as temperature decreases from 66F to 44F. Not as much of an increase as with the 162 grain Amax.</p><p></p><p>This is based on multiple chronographing sessions at a variety of temperatures. I'm providing averages based on sum of the chronograph data, as modeled by my ballistic software, LoadBase 3.0.</p><p></p><p>So I actually had a greater MV increase with decreasing temperatures with H1000 than I've had with Retumbo. But nothing close to 75fps. The increased muzzle velocities I've experienced are more like 5 to 25 fps. </p><p></p><p>Again, for the doubting Thomas's out there, this has been experienced over multiple chronographing sessions at a variety of temperatures from -5F to +75F, with between 2 to 4 chronographs recording each and every shot fired. And I have specifically allowed both the rife chamber, barrel, and ammo to cool down to ambient temperature prior to firing over the chronographs for the specific purpose of establishing muzzle velocity at varying ambient temperatures.</p><p></p><p>Whatever chemicals Hodgdon is applying to their Extreme line of gun powders, the result can be an increase in MV with decreasing temperature. But I have not experienced any velocity increases with decreasing temperature exceeding ~35fps. Never up to the 75fps increase mentioned by the OP.</p></blockquote><p></p>
[QUOTE="Pdvdh, post: 516193, member: 4191"] I just opened my ballistics software program to see if I had remembered correctly or not. Here's some data from my records - which is more accurate than my memory. The temperature versus muzzle velocity modeling for my 7mm Rem Mag with 74.6 grains Retumbo and the Berger 168 VLD: 77F = 3058fps 68F = 3054fps 59F = 3044fps 32F = 3039fps 14F = 3045fps 05F = 3044fps Pretty temperature stable from 5F to 59F. Here's the temperature versus MV data from my .280 RCBS 30-Degree Improved, loading 62.5 grains H1000, with the 162 grain Amax: 68F 2920fps 59F 2937fps 41F 2948fps 23F 2948fps Approximately 28fps [B]increase[/B] in MV as temperatures dropped from 68F to 41F with H1000. With the .280 RCBS Improved, H1000, and the 168 grain Berger VLD, I see about a 5fps increase in MV as temperature decreases from 66F to 44F. Not as much of an increase as with the 162 grain Amax. This is based on multiple chronographing sessions at a variety of temperatures. I'm providing averages based on sum of the chronograph data, as modeled by my ballistic software, LoadBase 3.0. So I actually had a greater MV increase with decreasing temperatures with H1000 than I've had with Retumbo. But nothing close to 75fps. The increased muzzle velocities I've experienced are more like 5 to 25 fps. Again, for the doubting Thomas's out there, this has been experienced over multiple chronographing sessions at a variety of temperatures from -5F to +75F, with between 2 to 4 chronographs recording each and every shot fired. And I have specifically allowed both the rife chamber, barrel, and ammo to cool down to ambient temperature prior to firing over the chronographs for the specific purpose of establishing muzzle velocity at varying ambient temperatures. Whatever chemicals Hodgdon is applying to their Extreme line of gun powders, the result can be an increase in MV with decreasing temperature. But I have not experienced any velocity increases with decreasing temperature exceeding ~35fps. Never up to the 75fps increase mentioned by the OP. [/QUOTE]
Insert quotes…
Verification
Post reply
Forums
Rifles, Reloading, Optics, Equipment
Reloading
Retumbo & Temperature
Top