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I live here in Portland, and I shoot mostly within a 75-mile radius of the city. But the things I have learned about differing temperatures can be applied anywhere. I also own property in N. Washington and sometimes shoot in Bend. Both of these places get colder than Portland.Yes, understanding this POI difference is the goal. I also need to track POI shift with elevation changes but its rare I get to target shoot in another part of the state but eventually will take a trip.
The POI decay is not linear. It's more exponential as projectile velocity decreases with yardage. And the colder it is, the denser the air is, and velocity decreases faster with yardage.10" @ 500 is only 2" @ 100 or with IMR powder 20°.
Hey @Xmark1 please excuse the dumb questions, but firstly I assume the 10 inch POI difference you mentioned earlier is entirely vertical (elevation) correct? Also, is the higher POI in summer? Thanks so much! Old Guy, but still learning here.I live here in Portland, and I shoot mostly within a 75-mile radius of the city. But the things I have learned about differing temperatures can be applied anywhere. I also own property in N. Washington and sometimes shoot in Bend. Both of these places get colder than Portland.
Long ago I started keeping a detailed logbook for each firearm I shoot. I made notes about where I was shooting, elevation, temperature, different hand loads, distance, wind, and much more. This habit has served me well.
Memories fade but notes don't lie.
When I started seeing things like changes in POI from when I started shooting midday to perhaps seven - or ten-degrees cooler as evening approached, it was a real eye opener! I am now so familiar with this phenomenon that as the day cools, I automatically increase my elevation dope. This is especially apparent when shooting 400+ yards. But since I shoot out to a mile (about 1,760 yards) it is a need-to-know skill.
Before I learned these things, I would pull my hair out wondering why my POI kept changing!
Perhaps I should note for newbies that this phenomenon is most apparent once you get past, say 250 yards.
My $.02
For the Accuracy-Analists here (such as I) 2 MOA is heart-breaking!10" @ 500 is only 2" @ 100
Gosh. The quite occasional unpredictables of long-range shooting. They are incalculable in number and rate.Holy Crap! That is a Big Difference!
I was not aware of that. Thanks for the education!
DAM, Spit.Gosh. The quite occasional unpredictables of long-range shooting. They are incalculable in number and rate.
Intriguing and amusing, A parlor game, which when applied to a living animal as a test subject is obscenity at its worst.
...But an admirable pursuit of valid achievement on the target field.
Yes and no. Like you, I find Butterbean's chart on LRH to be interesting but wonder at its source.so powder sensitivity is important for hunters to be aware of too.
Ha-ha. I had to read that twice as it's a trick question.Hey @Xmark1 please excuse the dumb questions, but firstly I assume the 10 inch POI difference you mentioned earlier is entirely vertical (elevation) correct? Also, is the higher POI in summer? Thanks so much! Old Guy, but still learning here.
Yes and no. Like you, I find Butterbean's chart on LRH to be interesting but wonder at its source.
As @Xmark1 noted, observation recorded in dope books is invaluable.
Hence, I don't worry too much about temp sensitivity, as a lot of the powders I load with are temp sensitive.
With today's prices and past scarcity, I work with what I have on hand. Beggars can't be choosers.
What I want to know, and take notes on, is what my loading will shoot out of my rifle under what conditions.
I seldom shoot at an animal out past 300 yards, but that's usually because this old fart can't see farther than that without glass.Gosh. The quite occasional unpredictables of long-range shooting. They are incalculable in number and rate.
Intriguing and amusing, A parlor game, which when applied to a living animal as a test subject is obscenity at its worst.
...But an admirable pursuit of valid achievement on the target field.
I should add to my statement that (for better or worse) there is a growing trend in long range hunting and for anyone who shoots over 300yds at game I think should be aware of the temperature stability of their load.Yes and no. Like you, I find Butterbean's chart on LRH to be interesting but wonder at its source.
Thank You Bro.Ha-ha. I had to read that twice as it's a trick question.
Let us assume you zeroed your rifle @ 87 degrees ambient temp in the summer. 100 yard zero, no wind.
So, if you use the same rifle that was doped for a 100 yard zero in the summer, in winter ---
Cold air is denser therefore it slows the projectile down faster than warm air. So, the winter POI will be lower. The elevation dope will need to be adjusted higher.
The change applies to elevation only, windage is a different subject. Let's assume for the sake of argument there is no wind. Then there is no effect on windage.
If there is wind, it will have a more powerful effect on your projectiles flight path because cold air is denser.
Personally, I dope elevation for a given temp/yardage with my turrets, but I correct for windage on the fly because the wind is constantly changing.
I haven't used RL22 but at the range your hunting you'd probably never notice. My guess is at 100yds, you'd have to shoot from a benchrest to notice any temp difference affecting POI.Once I was going to see what high temps would do to the cartridges, so I left 5 on the dash of the truck on a sunny day. I forgot them until I'd packed everything away...
I use RL22, which isn't supposed to be all that temp stable. I do most of my load development in the summer when it's fun to be out in the woods. I always recheck zero shortly before deer season when the temps are a little lower. 20-30 degree reduction, no difference. Once when we went elk hunting we needed to sight in my wife's rifle at camp. I tool the opportunity to check mine, too. 2000' more elevation and almost 50 degrees less temp and I put bullets in the same place as at "home". (all of this at 100 yards)
I do not hunt "long range". In fact, I've never even shot at a deer or elk past 70-75 yards.
Within the typical (for me) distances I shoot at, I've never been able to tell the difference when the temp is anywhere from the 20's to the 90's. If I had the place to consistently shoot at 400 yards it would be a much better test of this phenomenon.
Maybe RL22 isn't all that bad?
If I wasn't sitting on 7 or 8 pounds of RL22, I would try RL23. At the rate I'm going thru it, I have 10 lifetimes of it left! I have a great, accurate load for my Ackley (30-06) and will load up a bunch after I get the press mounted back up. But as soon as I can get back to loading, it's 257 Roberts time! I've not worked with a "new" cartridge since I started loading for the Ackley 5 or 6 years ago.I haven't used RL22 but at the range your hunting you'd probably never notice. My guess is at 100yds, you'd have to shoot from a benchrest to notice any temp difference affecting POI.
I doubt RL22 is "that" unstable that out in the woods over a backpack or whatever it would be noticeable at 100yds.
If you ever felt like experimenting, RL23 is supposed to be the temp stable version of RL22, it might be an easy swap in the recipe though I would run a pressure ladder to be sure.
I wouldnt change a thing then, I know what its like to invest in a supply of powder... eventually you have to use what you got. The RL22 might even work in your 257 Roberts with the heavier bullets.If I wasn't sitting on 7 or 8 pounds of RL22, I would try RL23. At the rate I'm going thru it, I have 10 lifetimes of it left! I have a great, accurate load for my Ackley (30-06) and will load up a bunch after I get the press mounted back up. But as soon as I can get back to loading, it's 257 Roberts time! I've not worked with a "new" cartridge since I started loading for the Ackley 5 or 6 years ago.
Maybe, but in this case I am going to take the advice of a very seasoned shooter/reloader and start with 4350.I wouldnt change a thing then, I know what its like to invest in a supply of powder... eventually you have to use what you got. The RL22 might even work in your 257 Roberts with the heavier bullets.