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Message: <blockquote data-quote="diggler1833" data-source="post: 3838174" data-attributes="member: 48072">This is pretty interesting.  Most people swear by the temperature insensitivity of H4350, yet you are having to back off a half grain, so probably we're experiencing a 2 FPS / degrre swing.In most of the tests I've seen conducted, H4350 is down around the .25 FPS / degree range...so theoretically whopping 25 FPS difference on a 20 degree vs 120 degree day.My H4350 experience is pretty limited, but I did develop a load for my first 6.5x47L last month in 95+ degree weather too.  I was using H4350 for it (see below).[ATTACH=full]294217[/ATTACH]I went with 39.4 and cut the difference between the targets on the left and center, and then shot a confirmation group at 385 yards (farthest I can shoot in a safe direction from my porch).[ATTACH=full]294219[/ATTACH]It'll be interesting to shoot this load in the winter and see how much velocity I lose.  I'm pretty curious now that I read about you having to drop a half grain.  It is something I expect with a powder like Re-15, CFE-223, TAC etc...  but not a Hodgdon extreme.  I have quite a bit of experience with Varget, and taking my M24R for example (7.62x51), my charge weight needs no change between 40 and 80 degrees...and unfortunately that barrel is pretty finicky about velocity.Did you change powder lots by chance?  I do know that at one point H4350 had a pretty significant swing in velocity, but that was years ago.How is your cleaning regimen?  Sometimes excessive copper, or even the dreaded donut will spike pressures and occasionally velocity.Sorry for the question volley...something is just not adding up in my head how you can get a 60 FPS swing over a 32 degree change with one of the most (if not the most) temperature stable powders on the market.Strange things happen though.</blockquote>

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