How does cold affect point of impact?
 

For a load that was worked up in the summer (80+ degree weather), what, if any, effect will the cold (below freezing) have on the expected point of impact?

Last year I used the FPBs for hunting. I had good success but wanted to see if I could work up a better accuracy load with the Speer GDHP in the 240/250 grain range, both .44 and .45 caliber. I’ve got a couple of bullet/sabot/powder loads that work well in my Omega X7, but they were all shot in pretty hot weather. Particularly because of the plastic sabot, I am wondering if I need to get out to the range on a really cold day to see if there is a difference. Maybe load up and let the barrel get really cold before shooting.

Anyone with experience on this?

[edited to correct poor terminology as pointed out by Sabotloader - Thanks!]

man, one time the barrel swetted on me and screwed me....now i make sure to unload, one way or another, and clean and reload in the morning before my hunt.i know this doesnt exactly relate to your thread, but if the gun dont shoot,
i think it has some impact here<<<<total pun

I have found that on some of my guns (but for some reason not all of them) the POI does change a little when the cold weather hits. But it's slight and would not be an issue in a hunting situation. But you have to remember that cold weather for me is the low 40's, and very cold is the low 30's. :biggrin:

Like Semisane said... some of my rifles change a little. I was shooting one morning and it was -18º and the first shot on a clean bore changed as much as three inches. The others were almost and inch and a half out of the bulls eye.

I want to do more cold weather testing this year. Its very interesting.

colder temps will lower velocity as with smokeless powders...

hubby11

Just a little correction in what I think you are asking... In cold weather you Point of Aim will remain the same - but the POI (Point of Impact) can change - not normally a drastic change @ 100 but a change... everything contracts a little more.

I truly believe the effects of the temperature are more dramatically felt in the sabot than anywhere else. As rdpettit suggested velocity change can and will occur with temperature change.

The sabot... heat is a killer. It is my un-scientific belief that that the Harvester Polymere compound is less effected by heat... it seems to be a harder compound and stands up to heat better. It is also my un-scientific belief that the MMP Polymere compound functions more uniformily in the colder temperatures. It seem softer and more pliable even at very cold temps and therefore loads and molds itself more tightly to the lands and grooves of the bore.

Again this all un-scientific...

I know it is a normal practice for me to sight in at or near the temperatures that I will be hunting in. In the summer - I very seldom touch a scope... it shoots where it shoots.....

Check my posts here over the last few weeks and the one from this past weekend. My gun will shoot 2" high and 2" right on the first shot out of a cold barrel. But that is in 80+ weather. Not sure how much more it will move in colder weather. I doubt it will move much, at least not enough to make a difference.

A friend of mine used my ML to whack a doe at about 200 yards, at -30 temps. This isn't exactly "data" but it must not have effected the shoot TOO much..

It seems to me like I have read that some powders are more affected then other. (talking about cold verses hot outside temp, not a hot or cold barrel) A hot barrel will raise the temp of the powder even if it is cold outside. I know this holds true with smokeless powders so I would think the same holds true with black powder. Out of my Omega, my groups using BH 209 stay the same. I would suggest a load with BH. The only real difference for me is clean verse fouled barrel.

I've never had any issues with this. Of course, the temperature changes haven't been too drastic. I've generally sighted my guns in during 65 - 75 degree weather. The coldest I've hunted in with a ML is around 15, with average hunting temps in the 30's and 40's. The bullet impact change (if there has been one) was not enough for me to notice.