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Temp sensitive powder and fps ?

 
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  #15  
Old 12-12-2013, 01:14 AM
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Join Date: Dec 2011
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Re: Temp sensitive powder and fps ?

Quote:
Originally Posted by Kennibear View Post
Re read you original post. Your chrono not reading is a problem. But you need to check the actual speed at 7F degrees. Hard to believe it is -200fps.

Huge density altitude change between your two range sessions. The cold one may have been at or below sea level DA. 55F @ 4500' altitude may be close to standard conditions. Dial in the changes in conditions and see how close it conforms.

Finding solutions to this sort of thing is the both frustrating and fascinating thing about this hobby. Kind of like women.....

KB
Your Density altitude alone could easily put you off by .5 mil. A chrony is usually +/-1%. There is your margin error. Your numbers ( fps, bc ) could be perfect, your can have 0temp variance and you could be off that much. Nothing replaces actually shooting at range and getting good DOPE.
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  #16  
Old 12-12-2013, 10:18 AM
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Location: Meridian, Idaho
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Re: Temp sensitive powder and fps ?

I believe I had the correct atmosphere conditions input and in order to be that far off it would have to be below sea level and -30 with powder temp turned on. According to the ballistics computer.

I will take the chrono out this weekend test some loads to see what number needs to be in the powder temp section. Based on Hogdon site it should be .36fps/degree. I will try and verify that. Temps here are 0-10F. I can stick some rounds next to my body and some outside and test the spread.

I think it is a combo of the temp sensitivity and lower BC. Berger and Nosler both have much lower BC numbers and both of those bullets are generally accepted to be of very good quality. In theory if I use .36 and a BC of .235 with 3800 FPS the elevation solution is very close. If my scope has some error I will try and rule that out as well.

Appreciate all the input and things to consider.
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  #17  
Old 12-12-2013, 11:21 AM
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Join Date: Jul 2012
Location: Washington State
Posts: 273
Re: Temp sensitive powder and fps ?

Scope, temp, BC, all these factors multiply.

In sighting in many (mine and friends) scopes I have never had exact movement of the group on target. As most people want their rigs sighted @ 200yds the movement should be two clicks per inch. I cannot recall that ever being the case. If memory serves the movements were always more, i.e. dial in adjustments, group moves too far, dial back to center up group. This is for typical hunting non - AO scopes. My ancient Weaver T16 is closest I remember but it was a smidgen off too. It didn't move enough as I recall. It's currently dialed in for a single load @ 100yds and I have't change it in years, probably frozen with rust at this point.

Don't know what turrets you have on the scope but I would check the screws just to be sure before I fired the next round. Probably do it at the bench just before shooting. I'm kinda annul that way. Found some loose scope ring screws time before last. It was actually a surprise as I Blue Locktite all my scope screws.

My vote is still BC = BS.

KB
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  #18  
Old 12-12-2013, 11:24 AM
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Join Date: Jul 2012
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Re: Temp sensitive powder and fps ?

P.S.

Am I the only one that thinks 0.36 fps/ degree is an incredibly good number???

KB
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  #19  
Old 12-12-2013, 01:23 PM
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Location: Meridian, Idaho
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Re: Temp sensitive powder and fps ?

I just got this scope back from Leupold who installed the m1's. My normal LR scope is Night Force, which tracks extremely well. However, that scope is on my 6.5-284 and I don't want to pull it off to conduct any testing.

When zeroing the Leupold it was quite responsive and I shot multiple .25 to .38 groups at 100. My last adjustment was .5 high and .25 right. 2 clicks down and 1 left put me on the black .5 square for 2, 3 round zeroing groups.

Not sure about .36 being good or not. I use retumbo in my 6.5-284 and my solutions on elevation have extremely good from 0 to 90, 2500 to 10200 ft, and out 1660 yards. This temp thing is a new issue for me. I figured I would have some issues with it and IMR powders, just was not sure how sensitive it might be. Kind of a fun learning opportunity.
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  #20  
Old 12-12-2013, 04:15 PM
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Re: Temp sensitive powder and fps ?

BrentM

All those powders, Hodgdon's Retumbo, H1000 etc. and the IMR series are manufactured by ADI in Australia for Hodgdon who now own the rights to DuPont's powder line. Hodgdon claimed to have applied the "Extreme" powder technology across their line after so much success with, I believe, "Varget" their first such powder.

Hard for me to believe that cold weather slows the powder at all this day in age....

But BC's haven't escaped the Ad department yet.....

KB
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  #21  
Old 12-12-2013, 05:25 PM
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Join Date: Jan 2013
Location: Meridian, Idaho
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Re: Temp sensitive powder and fps ?

Quote:
Originally Posted by Kennibear View Post
BrentM

All those powders, Hodgdon's Retumbo, H1000 etc. and the IMR series are manufactured by ADI in Australia for Hodgdon who now own the rights to DuPont's powder line. Hodgdon claimed to have applied the "Extreme" powder technology across their line after so much success with, I believe, "Varget" their first such powder.

Hard for me to believe that cold weather slows the powder at all this day in age....

But BC's haven't escaped the Ad department yet.....

KB

Understood. I think you are correct about the BC thing. This is not the first time I have heard or read about it. Looking at Litz info I can see the differences from claimed to actual pretty well. If I had been shooting a claimed temp stable powder my little brain might have gone straight to BC, but I blocked that out.

I appreciate all the input and variables everyone has discussed. I will test this weekend and finish dialing in the rifle. My kid and wife will use it for wolf hunting along with my 6.5 so I want it tuned up perfectly so they have confidence in it.
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