Efforts made both by automobile manufactures and coal burning industries over the years have helped to reduce the problem but nothing can be done about the location of Louisville next to the Ohio River or to the heat and humidity that comes every summer.
The same can be said about all atmospheric conditions. There is just nothing that we can do about weather conditions, except to understand that those conditions will effect our shooting performance. That understanding may help us when we make decisions about what we use, on particular days.
Recently, I had a conversation with a duck hunter who was having a real problem making clean kills on the ducks he was shooting. Sometimes, it required 2 or 3 good hits to bring down a duck. He’d not had this problem before and after all, he was hitting the ducks, not missing them but they just did not want to fall. Why?
It turned out that he was shooting in sub-zero temperatures, using steel shot shells and had a relatively short barrel on his shotgun. Why did that matter?
The performance of all ammunition is effected in some manner by temperature variations. At temperatures below zero, there may be a substantial decrease in the velocity at which the shot payload exit’s the muzzle and that effects the retained energy of the shot on the target. Add to that the fact that in those temperatures, very cold shotshell wads may not fully expand to fill the bore (especially in overbored barrels) and thus allow gas to escape that would normally propel the shot payload down the barrel faster. Most steel shotshells also use a powder with a slower burn rate than lead shotshells. Steel shotshells need a longer barrel to allow a full burn and to allow the shot to reach maximum muzzle velocity, that is usually measured from a 30” barrel.
Several factors combined to effect the performance of his gun and shotshell combination. If he'd had this knowlege before going hunting he could have made some changes and bettered his performance.
He could have decided to only take closer shots. He could have considered using a longer shotgun barrel. He could have used tungsten-based shot. He could have kept his shotshells warmer by keeping them close to his body until ready for use.
We can’t change the weather but we can alter what we shoot and how we shoot it or at least understand that we won’t get the same results when we shoot under different atmospheric conditions.
How does this relate to patterning our shotguns for hunting turkeys? We normally hunt turkeys in the Spring and if we’re lucky, in the Fall. Both of those seasons, in many parts of the country, are subject to swings in both temperature and humidity levels.
Many of us get out each Spring as soon as it warms up just a bit and go to the patterning board. We look at our results and lament over the performance.
We’ve read all those glowing reports and seen all those beautiful pictures of patterns that all the shooters have posted on all the many forums and message board that abound today. Why didn’t the patterns that we just shot look like those? We’ve bought the “latest and greatest” turkey choke and shotshells, what’s wrong?
There are probably a combination of reasons. The temperature and humidity when we shot were different than when they shot. Plus, we are seeing the reality of shooting in conditions that we can’t control and we’re not selecting the best of the targets that we’ve shot to post on a bulletin board.
We know that we’ll get better patterns when it’s at least above 60 degrees (generally the hotter the better) and when we have low humidity. A higher altitude will help but most of us can’t relocate just to pattern a shotgun.
Some major manufactures of shotshells have shared their experiences and expertise with us.
“We've found that low humidity gives better performance, as well." Environ-Metal, makers of Hevi-Shot products
“Air Density" does indeed affect patterns. There were even charts for correcting patterns back to "standard conditions" to be able to compare patterns shot on different days. This "Air Density" is determined from a combination of the temperature and barometric pressure. Humidity by itself has not generally been considered a factor.” Winchester Shotshell Division
“…down here--where it gets hot...we started noticing that the patterns got much tighter in the core in the afternoons. Every day. With shells from the same batch. The typical morning shooting was much more pleasant---70 degrees let's say...but heck, we might have been just above dew point---meaning that the relative humidity was very high. As the day warmed...the RH of course went down....and the core count went up. So--that is what I know about it.” Polywad, Inc. (The company that developed and loaded the "Old White" Hevi-13 shotshells.)
“Weather, such as wind, humidity, dew point, rain, and dense air will open your center pattern. The ideal condition is no wind, 60 degrees temperature, with no humidity or very low dew point. This is when all your testing should be done.” Nitro Company Ammunition
If we want to optimize our paper patterns, we should pick a hot and dry day. If we want to see how are gun/choke/shotshell will pattern on days that are more like those when we’ll hunt, we might want to pick a day that’s not ideal.
The best of both worlds would be to do both. It’s always good to know how your particular combination will fare no matter what the weather conditions.
What if you’re like the duck hunter and find that the combination that you’ve picked works very well when it’s hot and dry but not so well when the temperature drops and it’s wet outside? What do you do then?
Don't panic!. Don't run out and buy another shotgun, choke or even a box of shells just yet. Here's where the knowledge that you have becomes power and useful.
If your combo doesn’t pattern well at 40 yards on cold wet days, how does it pattern at 30 yards? Maybe you need to consider shorter shots on cold or wet days.
Are you shooting a short barrel because you like the way it handles in the turkey woods? Do you have a longer barrel that you can try on cold or wet days to see if the added length and resulting added muzzle velocity will help your patterns?
What shotshell are you using? Have you tried a “change-up” between lead shot and tungsten shot? Even if you’re a died-in-the-wool lead shot shooter, you might want to try a more dense shot when the air is "wetter". Save your lead for the blue bird days and use the “hard” shot on the nasty ones.
Have you really cleaned your gun barrel? A dirty barrel with plastic and unburned powder residue might not hurt your pattern that much when it’s hot and dry but on a cold wet day, when everything is less efficient, it might just be enough to be the difference.
Lastly, we must always remember that patterns are about killing turkeys and not killing paper. We’re looking for dense and even patterns in something like 10” to 20”, not clumps of shot . We certainly don’t need 200 holes in 10” to have a good pattern.
We’re looking for something that we have confidence in to kill a turkey at a range that we are willing and capable of shooting.
I encourage you to pattern your gun in all seasons if possible and recommend the article found at http://allaboutshooting.com/article_info.php?articles_id=302as a place to start.
If you have questions or run into problems in the process, please feel free to take advantage of the free, no obligation service, “The Shooting System”, available at http://allaboutshooting.com/index.php
This article was originally published on this site on July 13, 2009.