How much does the temp have to do with changes in accuracy?????
Lets say you found a very good load and bullet combo at 80 or 90 degrees,but,at mid to low 40's it is nowhere near where it was all summer! What do you do? Start over?????
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How much does the temp have to do with changes in accuracy?????
Lets say you found a very good load and bullet combo at 80 or 90 degrees,but,at mid to low 40's it is nowhere near where it was all summer! What do you do? Start over?????
With temperature sensitive powders, As temp goes up and down you decrease and increase powder weight to account for the differences in how the powder behaves.
If you are using Hodgdons EXTREME line of powders, they are not sensitive to temp changes.
I have 2 IMR 3031 loads for my .220 swift. One will shoot 1/2" and the other will shoot 1". The problem is which one will do what as the switch places when the weather changes.
A buddy of mine has dope for is .300 WSM with RL22 and his elevation at 800 yards is only a 3" difference from 15*F and 110* F. The difference in point of impact is an inch or less out to 600 yards where it goes up to 1.1".
The only way to get great accuracy is to keep a log, and do load developement in all the tempratures that you would shoot in, then refer back to you log, and use that info. I would also record lot number, time of day, Humidity, as well as temprature.
ALL gun powder is sensitive to change. Gun powder will change as the day go on, powder will weigh heavier in the morning, and as the day goes on it will weigh less, with majority of powder measurers measuring powder by volume and not by weight, (One of the nice features of a eletronic powder measurer, is it measures by weight.) this causes a need for the powder charge to be tweeked as the day goes on.
How does powder, in a sealed waterproof/airtight container, know what time of day it is?
As an artillery guy, I can tell you we don't do anything with the clock when it comes to powders...temp, yes, but time of day is irrelevant. We also don't weight the powder. The contents dot change, but the temp affects velocity.
Or the humidity? Oh, he's talking about LOADING rounds, not firing them.Quote:
Originally Posted by rrflyer
KeS
When you open the powder up, and put it in your powder measurer, so that it can be meatered in to the case it is no longer in a "sealed waterproof/airtight container."Quote:
Originally Posted by rrflyer
Many competitive Benchrest shooters know that this happens, and will have to adjust there powder from morning as the day goes on onto the evening.
I know the hotter temps will cause my 308 to do some weird things..At one match,I screwed up and left my ammo
in the sun..My first relay was 98 ...With the hot ammo the 2nd relay was like a 72 out of 100...I almost decided not
to shoot the relay..But figured,what the hell...I knew it was not going to be good..So remember keep your ammo in
the shade...I have never really seen too much difference in the colder temps....
Quote:
Originally Posted by rrflyer
...the same way that my Thermos bottle knows whether to keep hot things hot or to keep cold things cold.! :rolleyes:
...and that's all I have to say about that. :focus:
Good one Forest---good one:baby:Quote:
Originally Posted by thomae
Rifle chamber temperature has a much greater impact on pressure than ambient temperature. Denton Bramwell has done some well-instrumented testing of this. Search for his 2 papers on the topic; I don't have the URLs conveniently at hand or I'd link directly to them. I think 6mmbr has one of them on their site, and RSI the other, but I'm not positive. Sniper's Hide has, I think, at least one of them.
This is a commonly-held fallacy. In fact, temperature resistance IS NOT an across-the-board thing. The temp-resistance only holds within a design window that's to do with case capacity, bore diameter, bullet weight, etc. The harder you try to make perfect resistance, the worse the temp-resistance gets when you use the powder outside its design envelope.Quote:
Originally Posted by seanhagerty
To the OP...the true answer to your question is... "It Depends"
your powder choice, optimal pressure in of your cartridge in your rifle, in specific atmospheric conditions etc... etc...
All these things are minimized by using a powder that has a high resistence to temperature change.
If you've chosen a powder that is very temp sensitive then yes..basically you start all over.
Now as to the other guys who are saying that the time of day effects powder...well thats a bunch of ....well... bull hockey.
Yes generally the day gets hotter as it goes along and yes generally hotter temps mean high pressure in your ammo and that means...well who knows in your rifle.
But generally doesn't mean squat in this case.
It all very much depends on what "game" you want to play. Most of the people I know buy a specific lot of powder. Load 500 to 1,000 rounds and then re-chrono when those rounds run out and are re-loaded.
Those cartridges are sealed "containers" and I've yet to see one with a sighting window so the powder can get the angle of the sun.
If your a benchrest guy counting clicks on a harrels measure and loading as you sit there it is a different deal altogether and you may not know what your specific charge weight is...merely you add a click when the temp or humidy or whatever does its thing.
82boy was right in saying the only true way to know is to keep a log. Buying large amounts of the same lot of powder, case, bullet, primer, will increase consistency and ease your record keeping.
I find it easier to make a load with a temp insensitive powder and choot 'em.
Please explainQuote:
Originally Posted by MZ5
I believe what he's saying is "powder X" is designed to have a high resistence to change within a certain temperature range. Furthermore that range of resistence is optimzed for certain calibers and bullets.
Like "powder X' has a minimum velocity change from 80F to 110F when used with a 308 cartridge and 175gn bullet at a pressure range of Y to Z.
Trying to make "Powder X" zero or no velocity change inside those specific conditions means that as soon as you step outside those design specs that everything goes to crap quickly.
SO...just becuase your using a "extreme" or "temp stable" powder doesn't mean thatll itll work very well if using it in a 223 when it was developed for use in 308win.
I think I have read some of this stuff in a shootin magazine afor...
What it means if ,say your shooting several rounds and you load another and close the actionQuote:
Originally Posted by M.O.A.
and let the round set there it is going to be getting hot from the temp's already in there...Sort
of like I said about leaving your ammo set in the sun befor shooting it.There will be some
very noticeable changes in everything...I think it best if you try this to see for yourself...
It is very interesting....
Thanks, guys. :)
Here are the links to Bramwell's articles:
http://www.shootingsoftware.com/ftp/...%20Factors.pdf
http://www.snipershide.com/UserFiles...periment_2.pdf
Also, Accurate/Ramshot has the best info I've seen from a powder company on temp resistance. See their FAQ section at:
http://www.accuratepowder.com/faq/
At the Accurate site, it's question #7. On the Ramshot side, it's question #5.
MOA,
Along with that, please remember that advertised claims and reality aren't always the same thing.
If you go to Hodgdon's website and look over the "tests" comparing how magical their extreme properties are, you will see several things.
1) Absolutely no relevant testing info is given(number of shots, SD, time in chamber, etc)
2) That RELATIVELY speaking, there is NOT much difference, and in the case of the 22-250, No tangible difference.
In the 22-250, the Extreme powder beat its next competitor by 6 fps. Regardless of sample size, that is not statistically a difference. The next in that line is only 16 fps off. How often are your ES numbers in the single digits with standard loads anyway??
ok guys i thinks i got what you is selling here ;-}
on the TV show best of the west they had a box of 7mm mags sitting in cooler full of ice and one sitting in the sun they said the ones in the sun where like 98 or so and the ones in the ice where at like 23 or so there where two loads in both one with extreme powder and the othere was not anywas the extreme did have a less of a spreed.
but there again its all advertisment anyway
So,it all comes down to loading for the temp and try to keep records of it all. I've done this for years.