I checked the zero on one of my flinters this fall a couple of weeks before season. Well I get a shot at a deer on friday and hit a tree to the left of the deer and it felt like I put a good move one it. Later on in the day I get another chance and hit this deer in the spine toward the hind quarters. The deer was down but I couldn't believe how poor my shooting had been during the friday drives.
I checked the zero and it was shooting left about a foot so it had to be the stock swelling from getting really wet the day of the heavy snow here; I couldn't keep my gun dry that day and it had never happened to me in all my years of flinting. Anyway; they can change point of impact.
I know you should never break a rifle down after it's been wet and leave it that way or it can warp bigtime in short order. I left the sights just the way they were and went to a backup rifle. I can't wait to see if it returns to zero after it dries out real good.
Wood may expand or warp but I've never heard of a steel barrel and it's sights being affected by cold or wet weather. If the wood contracts, the barrel and sights stay the same. What changes is perhaps your clothing and reaction to cold temperatures, and perhaps a moving deer?
I don't see how. You could take your stock and turn it into a pretzel shape, but as long as you don't move your sights how could it change POI? Unless you're holding your rifle a bit different. Now a clean or fouled barrel, yes.
I have always had an issue with that. I can see how the warpage of a heavy wooden stock on a bolt action rifle can cause some changes to them relatively skinny barrels but to have the flimsy stock on a ML effect the hunk of iron that ML barrels are made of is something I find hard to accept. I have been shooting ML for about 25 years and I have never found the cold or heat to have any effece on POI. I have found the humidity to have an effect on the lock-time, the patch lube viscosity and the frequency that I need to brush and swab the bore. If heat or cold is going to effect the barrel it will be from direct effect to the metal, not the stock.
It is a common belief that high end synthtic and laminate stocks produce more consisted accuracy do to the unlikely hood of swelling due to humity or other dampness. Technically its change in vibration I believe when things contact your barrel differently that changes the POI
Temperature and humidity can have a small change on point of impact. The metal barrel doesn't have to change much, just a millimeter is sufficient. The stresses of the distance between the tang and barrel fasteners, can cause an ever so slight change. That is why on long rifles the barrel tannons should be slotted slightly instead of just round holes for the pins. Not only can the temperature changes affect a difference in distance between the wood and metal attachments, humidity can cause the wood to swell and shrink.
Will it throw a ball two feet to the side? Hardly. but in a hundred yards can it mean a couple inches, yes.
No body is saying the barrels bend like slinkies, but a four foot barrel does change in length by about a half millimeter just from zero degrees to 100 degrees. Foundries figure that iron shrinks by 10% from just poured molten iron to room temperature and make their casting molds 10% larger to accommodate the shrinkage. Ever see a board curl after it has been left laying on the damp ground? From the moisture swelling the contact side. Metal can bow ever so slightly just from temperature changes between one side and another. The old narrow military barrels that were held in with barrel bands were very prone to having a different point of impact between the first cold shot and when heated either by firing or ambient temperature. My trapdoor starts out 4 inches out on the first cold shot, and as the barrel heats slowly comes to center, by about the 5th shot. Muzzle loader barrels are far less subject to such changes but slight changes do occur.