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Old December 3, 2011, 04:33 AM   #51
BruceM
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"Hunting in Tundra does not have a lot to do with temperture sensitivity. I'm sure your rifle shoots good in cold wheather, but how much change to you get when you go from -15 to +100."

Actually, I have never hunted when the temperature was 100 degrees F and I think you'll find 90% of folks out there haven't either. The fact is that all propellants show some type of temperature sensitivity if you want to call it that. When I think of temperature sensitive propellants, I assume that this sensitivity is manifest in erratic behavior and not a characteristic that is common in most. Bluedot is a example of that type of erratic behavior when comparing pressure in context with various ambient temperatures.

A number of years back, there was a fascinating article in Shooting Times about this very subject. The gist of the article was that all ammo is subject to this phenomenon where as the temperature drops, so does velocity. Obviously, as range increases, POI changes also. I personally am not in the habit of zeroing or checking zero in mid summer when I intend to use the rifle in early winter or very late fall. I assumed that the majority of hunters do not either but I've been wrong before. Because this rolloff of velocity was observed in various brand of ammunition tested, the suggestion was that your rifle's zero should be verified under conditions approximating the conditions you plan to use it in if at all possible and, if not possible, to keep this velocity loss in mind. For that matter, the same advise can be given when large changes in elevation above sea level are anticipated. For most hunters, the shift in POI due to temperature shift is not a factor but for some, it obviously will be.

I guess that what I'm trying to say is that most propellants react, in general, in the manor you described. IMR 4350 does not seem to be extreme in this aspect. As I recall, the article suggested that velocities could vary up to 200 FPS or more. Does that mean that H4350 might be less subject to these variations, I don't know. I cannot speak to the new Extreme series of powders either. I do know that for most users, it's a non-issue although it probably is for a few. Where I hunt, the temperature can be in a range from +50 degrees F to -20 degrees F but these are the widest possible extremes and typically, the spread is much smaller.

It's funny but I do not seem to recall any loading manuals addressing pressure changes due to extremes in temperature in any length or detail but I admit that I haven't read them all. It would seem that although it is a factor, it resides pretty low on the totem pole of potential concerns. There are always scenarios which can be constructed where this could be a factor such as in military ammunition but, for the most part, it's wouldn't appear to be an issue for the everyday handloader.

Anyway.................

Bruce
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Old December 3, 2011, 05:25 AM   #52
Nnobby45
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Don't know if IMR4350 is more or less sensitive temp. wise.

Handloaders who like to load right at maximum pressures would be very well advised to understand the velocity/pressure increases associated with weather hotter than when the load was developed and tested.

The 200 fps increase in velocity you mentioned would represent a significant increase in pressure and could occur from the abient temperature alone.

Now consider the increased temp., beyond that, that occurs when the ammo is left in the hot sun.
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Old December 3, 2011, 01:35 PM   #53
black mamba
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It's why I do my load development in the summer when the temps are in the 80s (F). Then I know they are safe at anytime.
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Old December 4, 2011, 04:55 AM   #54
BruceM
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It's not a safety issue but rather the change in the point of impact that needs to be dealt with. Even then, it probably isn't a concern out to 200 meters or so in a medium to big game hunting situation. For it to be a significant safety issue, your charge weight would also have to be significantly beyond published maximums.

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Old December 29, 2011, 10:36 AM   #55
whtwolf06
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Ok thanks for all the great info! Now I have started with a few rounds at different grains, but the problem I have now is ... Loose bullets

Everything was going great until the crimp, I know not everyone needs to crimp but I do and plan on doing it. Well I am crimping at 3.250 col and as it is it's at the cannulure but when I crimp the bullet is slightly loose to the touch. Some say it is caused by over crimping?? If so how does one know when enough crimp is enough?? Should I seat the bullets more or less around the cannulure? Thanks again
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Old January 17, 2012, 08:34 AM   #56
whtwolf06
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Ok thanks again for the info/help. Seems the problem is solved, re worked the crimp and made same adjustments. Now just working the powder loads up then to the range to test will post results
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Old February 8, 2012, 08:16 AM   #57
whtwolf06
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ok test results in. 0.50 -0.75 inch group at 100 yards with 58.5grs h4350 C.O.L of 3.240, think this one is done and for the book. thx again for the info, crimp problem fixed.
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pic of group posted under pictures at fatherandsonreloading.weebly.com
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Old February 8, 2012, 04:34 PM   #58
Uncle Buck
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Powder Valley (http://www.powdervalleyinc.com/) has it, and other powders, cheaper than I can buy them locally.

They are having a pretty good deal on CCI, Tula, Winchester and Wolf primers.
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