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Old December 4, 2009, 11:57 AM   #1
Join Date: December 2, 2009
Location: garland tx
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newbie question does weather effect accuracy

first off i just want to tell everyone how much i like yalls forum. i just found it a couple of days ago. i started reloading a year ago this christmas and i love it.
the problem i ran into last night was my 150gr nossler accubond load from 2 months ago would not hold a group last night. i used 51 grains of imr 4895 in a browning a bolt 30-06. when i shoot this load 3 weeks ago i was sub moa. the only diffrence i can think of was that it was 35 degreese colder last night but i dont know if weather matters that much.(it was 40 F in garland tx) but on a diffrent note i put 3 shots of 57.5 gr imr 4831 150 gr hornady btsp through a .45 inch whole. i cleaned the gun at the range and tried the nosslers again and i had the same problem of bullets going left and right and one was 2.5 low. thanks in advance for the help and i hope everyone has a great weekend.
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Old December 4, 2009, 12:57 PM   #2
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Weather will effect proformance of your load. Temp, humidity, barmetric pressure, wind.

Develop your load during the time of year you'll be shooting.

Its hard to build a load in July & expect the same accuracy out of it in nov, dec, jan.

We all do it.

Your load should be "close enough" or "minute of coyote"
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Old December 4, 2009, 01:06 PM   #3
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QBall is exactly right.
I work on fall hunting loads at 35 degrees and prairie dog loads at 85 degrees.
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Old December 4, 2009, 01:37 PM   #4
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Welcome to the forum XD.

Yes weather, especially temp, will affect accuracy of a given load / gun combo.

No offense meant, but please consider the effects of weather on the shooter also. I know for a fact that I don't shoot very well when it's so cold I can't feel the trigger, or so hot I have sweat running into my eyes constantly!

I'm no Carlos Hathcock, and I'll be the first to admit it!!

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Old December 4, 2009, 01:59 PM   #5
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What about shooting in the rain? Anyone have an opinion? I sure even in a light rain a bullet traveling 100 yards down range is bound to hit a drop or two.
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Old December 4, 2009, 02:07 PM   #6
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Depends on how you define accuracy... if you sight your firearm in at 85 degrees and it is now 32 degrees, then your bullet will probably not hit where the crosshairs are pointing. However, I would anticipate that your bullets should impact the target with the same grouping as normal, just in a different spot on the target. So grouping size should be roughly the same, just hitting in a different spot on the target.
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Old December 4, 2009, 08:27 PM   #7
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I'm in Indiana. I reload & shoot 'year round. For me, the extreme powders work well all year. As stated above when the seasons change, my point of impact changes but the groups are the same relative to POI. I just adjust my scope or sights as the seasons change. You have to spend time at the range to know what your firearms are doing.
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Old December 4, 2009, 08:35 PM   #8
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What about shooting in the rain? Anyone have an opinion? I sure even in a light rain a bullet traveling 100 yards down range is bound to hit a drop or two.
I don't mind shooting in the rain or snow, as long as I've got cover overhead,,targets get kinda soggy tho. Sometimes you can see the bullet vortex during a downpour. Shooting prone in the snow is fun. Hard rain or snow can make the target hard to see at 100 yds.
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Old December 5, 2009, 12:36 PM   #9
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Try a 22-250 when foggy , way

The drops hittin the bullet????? alot of variables there !!!!
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Old December 5, 2009, 02:29 PM   #10
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Here's a link to an article about this subject. It seems that a biathlon competitor found out the hard way that a certain brand of ammo that grouped well in normal temperatures did not do so in extreme cold.
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Old December 5, 2009, 04:03 PM   #11
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Unless the rain is very heavy, the odds of a drop hitting a bullet are very small.

Rain is just not that dense.

Think about rain rates in fractions of an inch per hour.

There is just not that much water in a volume of air the size of a bullet from the muzzle to the target.
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Old December 5, 2009, 06:54 PM   #12
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Not long ago on one of the BR sites an informal survey was taken among the point blank (100 to 200 yard) competitive shooters. These folks put a pot of rounds down range in a year. The general consensus was that groups could not be said to be affected by weather until a temperature change of 20 degrees Fahrenheit had occurred. A lot of BR shooters load at the match and keep close records of how the loads do under all conditions and when they felt obliged to change the load and etc. A lot of the people commenting on the subject did not feel the need to adjust loads due to changes in humidity or barometric pressure. Long range (600 to 1000 yards) BR shooters do things differently, but apparently the vast majority of casual shooters (hunters, plinkers, etc. shoot within 200 yards, so I would think the opinions of these folks would be relevant especially as they shoot groups and rifles that are more responsive to small changes in the loads and environment. They are also more concerned with the weather than most of the people I used to see on the range on weekends--when I put out wind flags it was considered an oddity................

20 degrees and to hell with pressure and humidity did not sound right to me; I had even gone so far as to buy a portable barometer/temp/wind meter and check the humidity in my area before a match or practice session and after. I also have kept detailed records of all that for over 30 years, so I thought I would dig into my "archives" and disprove this bunch of nonsense. What
I remembered was wrong. What I read caused me to reconsider.

So, this year, since I am now confined to shooting at no longer range than 200 yards, unless I can get a ride from someone else going up to compete in Tacoma, I shot the same load in my BR rifles all year. Looking back, I can say that temperature did seem to have an effect at around a variation of 20 degrees. I get a chance to shoot in temps in the 50's a lot here, so I try to do any load development between 55 and 65 degrees if I can. Groups changed when temps were in the low 40's and in the 80's. Unless the humidity was so high that it turned into rain, I did not see a lot of change. Pressure was not even remotely a consideration. The rainy days were usually cooler days, but we have lots of those in the 50's so I think I had a pretty good sampling of temp variation without humidity variation and vice versa. Of course this is all very unscientific because the groups are subject to pilot error, when shot off a rest and rear bag, but as far as I can see it saves me a lot of fiddling with loads that I was doing previously.
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