I know I have see charts that give you some idea as to the efecet temp has on Velocity but not sure were. I am wondering as I checked some loads yesterday in 10 deg. weather and velocity seemed slower than I expected. I was only getting 3550fps out of a 22-250 with 35.3gr IMR 4064 win, primer 50 gr V-Mav. Hornady has thet loaded rated at 3700 & I thought 150ft was a lot. It shot great so I am thinking of working some more with it but this is a little slow from a 22-25. Let me know what you think.

Somewhere I seem to remember a figure of 2 fps/deg temp change. I believe this was when useing IMR powders. I`ve found it to be real close when cronoing loads in my experiance.

As low temperatures not only have an effect on the powder burn rate but on the electronics of the chronometer as well, you'd better check if impacts are lower than usual.

If you do not want to live with it, you can
a) increase the amount of powder a bit - which is "winter ammo" and can, if used in summer, yield dangerously high pressures, or
b) after some fouling shots, leave the cartridge a while in the chamber before firing or have your ammo in a pocket close to your body. While the first part of the sentence applies to target shooters only, the second part is a good advice for hunters anyway.

22/250 vs .308 shouldn't be relative to the following. Each will act differently due to the powder used but the theory is still good. Temperature affects 3 things. First the firer, no an issue here. Second is the ammunition and third the air. When ammunition sits in the sunlight the burn rate of the powder is increased, resulting in increased muzzle velocity and higher impact. The greatest affect is on the density of the air. As the temperature rises, the air density is lowered. Since there is less resistance the vel. increases and the point of impact raises. This is in relation to the initial temperature that the rifle was zeroed. As a general rule 20 degrees temp change will result in bullet impact +/- 1 MOA. I know this is basic stuff that you probably already know, however, most around me don't take this into consideration when reloading. Most just want to see max speed and group size. They go out on a sunny day when it is comfortable to shoot and that is their basis for bullet performance. Another basic lesson is that 20% change in humidity is also about 1 MOA. If you are comparing your results with someone else data you pretty much need to be there in the same environment. Was it hot, are they in a low humidity environment. Are they shooting bolt action or automatic, by wrote it should be bolt action. Powder..are you using a new can or old. The best way to tell you peak performance is of course to pick a hot but not humid day with no wind, 10 degrees is a hard spot to judge from. Use you computer and make a spreadsheet. Log all of the factors. Repeat at as many different temp/humidity combinations as you can. From that you can extrapolate your data. The missing value of 150 isn't relative unless you are trying to see just how close you can come to blowing up your rifle. From the data you will know what corrections and where on the target you need to shoot to have a killing shot, head or heart. If you are worried about group size then you have t also look at the shooter and the weapon constants. Really doesn't matter what you are shooting at the 22-250 will can them with factory loads so you really should be looking at the accuracy that you can accomplish and not the speed at which it travels. Again that accuracy isn't so much where the bullet impacts but whether or not you know when, where and how to correct it. Sorry for the rant but most people around me tout speed and I can out shoot them with a beat up old farm gun using factory loads. Enough said and again sorry, hope this answered you question. FYI 1 MOA = 1 inch at 100 meters, 2 inches at 200 meters and so on. Data collected should be the following: Date, Ammunition Type(consistant construction), Light, Mirage, Temp, Hour, Wind, Elevation, Windage, Shot impact, rifle, scope. And remember that if you hold your rilfe at a slight cant on a shot it can be of as much as 1/2 inch. Ok,,I'm done now.

Steve That is just what I was looking for Should have know to check out you site first.

Nearing Sniper Good info I have not seen that before. I didn't think about why my poi changed in cold weather. I am not a speed demen but thought that was lower than it chould be & useing Steves chart I would be almost were I thought I would be. Thanks Guy