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What Effect Does Temp And Altitude Have On Pf?


Andy

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I normally shoot in the Sacramento area (100 or 200 feet above sea level) but would like to shoot the Best of the Best match in Reno.

What effect can I expect from shooting at a higher elevation (however high Reno is).

Also what effect will warmer temps have on PF?

Andy

Shooting 5.1 of vv n320 behind a 180 MG 40 S&W.

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I think what Jeff is saying is that VV 3N37, for example, is not sensitive to altitude and temp differences.

I think the answer to your question as stated is that it depends on several factors. First and most obviousl is powder. Some a are sensitive to temperature and/or altitude, some are not. Second is OAL and free space in the loaded round which the powder has room to move. I'm sorry, but I think it really depends on all of those factors in concert.

A different question you might pose is something like "I load with 4.5 grains of Titegroup under a Star 180 JHP @ 1.187" OAL, has anyone experienced PF changes due to altitude and temp". Not a better question, just different.

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I have been using 3N37 for 10 years, it was originally designed a as rimfire powder!!

I have used it EVRYWHERE in the world and never had a problem, from the altitude of Brazilia to the humidity of the philliphines, up mountains and down valleys. I have never had more then a 1 point deviation.

If you are working with a new powder, try the temp test, one lot in a cooler and one lot warmed up. Its something I have done with new powders.

Shame the manufactures don't have stats for this......

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No worries with that load at that location at that time of the year. (Same powder and bullet I use.)

I'd only worry about Viht. powders if I was close to the power factor floor and I was shooting in well below-freezing temps.

Now if you had something like 231 you may be in trouble.

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The manufacturers do have all that data, but for most reloaders it isn't relevant. Sure, a varmint shooter might notice a change in poi, going from low to high or vice versa. But a deer hunter? Never.

The minute changes we're worried about fall within the changes the manufacturers deem allowable. So what (in the makers view) that going from the coast to the mountains your load went from 171PF to 164? That represents a 4% change in velocity, and when you consider how many variables are involved (temperature, humidity, air density, different chronograph, how much coffee you had for breakfast) posting charts for the changes is just asking for trouble.

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