Home Forums Hunting & Shooting Rimfires .22lr ammo point of impact change in really cold weather ?

Has anyone seen any studies or trials on how cold weather changes the point of impact with .22lr ammo in a rifle?

I know that the distances aren't long but wondered about the change in say from 10* to 100* at 75 yards.

American Rifleman did a study on this quite a few years ago, not only does point of impact change but accuracy decreased dramatically as temps went down. In my memory the ammo that did the best was Russian biathlon ammo so if you are looking for some good cold weather 22 ammo you might try finding out what biathlon shooters use.

drover

I plinked last winter with 5-6 different kinds of ammo in my Marlin. I wanted to see which brand shot the best. Range was short, 30-ish yards and I was shooting 7 shot groups. It was probably -20 or -25C out at our winter camp.

After my first 2-3 groups, I was ready to throw the gun away. I had grapefruit to cantaloupe sized groups. Figured I would keep going, since it might just be the ammo. After 7-8 groups (I went back and re-shot some brands), with the best performing ammo, I had 5 of the 7 shots in a ragged hole. I was amazed at how the groups shrank and shrank as I kept shooting. Really opened my eyes to cold weather performance, especially when you only get one shot hunting small game in the winter.

That doesn't really answer your question. I saw no repeatable difference in how the point of impact shifted compared to warm weather. But I use the same gun to hunt in the fall (0 to -15C) and never change the scope settings. It still knocks down birds and hares.

go to Winchesters website and run their ballistic calculator for 22lr. It shows effects with temperature change and shows projected drift and drop changes.

There's a couple things going on with rimfire ammo in colder temps. Bullets with wax-based lubes get thick and don't lube the barrel as effectively in cold temps. The lube density will change in the barrel from thinner near the warmer chamber to thicker/stickier toward the cooler muzzle. This thick lube on the bullet is also easily scraped off as it enters the chamber, more so on a tight match chamber. (I get much more wax build-up around the edges of the chamber in cold weather) This makes for less wax available to fully coat the full length of the bore. This will reduce velocity. Cold will also affect the burn rate of the powder, again resulting in lower velocity.

Cold air is denser and will offer more resistance to the bullet than warmer air. This denser air will increase the rate of the bullet's deceleration. This cold denser air will also increase wind drift. Cold air has more mass, therefore, a wind of a certain velocity will impart more energy on the bullet in the cold than in warmer air.

All these factors can/will cause an impact change in cold weather. Biathlon ammo has a lube that is designed to work better in cold weather and is usually loaded a little hotter than most regular match ammo, but still remain sub-sonic.

I sent back a Marlin/Rem model 60 with some functioning problems and got it back yesterday all fixed. Put the scope back on it last night and decided to resight the darn thing in again. The rifle functioned flawlessly but the trigger pull still left me wondering at times if the safety was still on in comparison to some tricked out 10/22's we have. Marlin/Rem replaced the whole action bar so perhaps it just needs a lot more rounds down the tube.

Shot the first group at 25 yards and surprisingly the scope did not need any adjustment but the group size wasn't great. Moved the target back to 75 yards, which is where we sight in all our .22's at, and made one adjustment to the scope setting to get it shooting where I wanted it to.

This rifle has not been a truly accurate shooter to begin with and the group sizes have never been under 1.25" at 75 yards. Today the groups seemed to be 2x or even 3x that size when the temp was 21* with no wind. It was a wee bit nippy but I got it close and I'll finish dialing it in if needed when the temps go above 60*.

I was using CCI Mini Mags and a couple of them sounded different from the rest. Not the sound that the gun makes when the last shot holds open the bolt but before that. That would surprise me as that ammo has a great reputation and maybe I misheard it with my ear protection on.

Seems like the cold does affect the group size.

What is the best option for sighting in when you can be hunting squirrels in August at 90 degrees and then in January at 20 degrees? I hate to sight in with every 20 degree change, especially with the shortage.

From my experience, you are good from 90s thru the 40s. It's when it gets below freezing that things can get wonky. It also will depend on the type of ammo you have and the lube they use. Wax/tallow based lubes (as used on match ammo) are the most temp sensitive. You'll know when it's time to sight it in again. As a .22 target shooter, I sight-in at every match. I often have to make little adjustments. But then I'm trying to hit a little dot at 50 yds. Temperature related changes at closer ranges will likely still result in a hit on a squirrel. It shouldn't take more than 6 shots to re-sight it in. Remember to pay attention to the wind, those little .22s get blown around pretty good.