During Extended Shooting, Your Rifle Barrel Needs
A Little Help Coming Back To Room Temperature.
Most of us don’t have our own private range, and in an increasingly urban society, probably have to travel at least a few miles to test our rifle handloads. Consequently we don’t get to a range as often as we’d like, and try to get in a lot of shooting when we do. This means the barrels of our rifles get warm, if not downright hot.
A little heat doesn’t make much difference, and there’s no way to keep barrels absolutely chilled except by not shooting the gun. (Even if the outside feels cool, be assured the bore warms up.) And contrary to popular belief, firing more than three shots quickly doesn’t cause good barrels to warp or groups to open up. A barrel that’s been properly heat-treated will keep plunking bullets into the same place even when hot enough to burn fingertips. Instead, groups open up after three shots because of odds: Even with the most accurate barrels made, shot by really good benchrest shooters, 5-shot groups average larger than 3-shot groups. One statistician even figured out a 7-shot group is the least number of shots required to truly measure the potential accuracy of a rifle.
Still, heat can make a difference in other ways. A hot barrel on a calm day sends heat-waves rising in front of a rifle’s scope, making aiming less than precise—and I can assure more southerly shooters it occurs even on January days in Montana. In fact it’s often worse on cold days, because just a little heat rising off the barrel roils up cold, dense air more than warm air. But that problem’s easily solved by the benchrester’s trick of sticking a paper tube on the front end of the scope. A rolled-up target and some masking tape will do the trick.
Two techniques for helping barrels cool are to rotate several rifles,
standing them in the shade with the actions open to allow cooler
air to rise through the bores.
Nope, the major problem in barrel heat isn’t warped barrels or aiming, but heat erosion. If we want an accurate barrel to remain accurate, we shouldn’t fire it much when it’s really hot, an ideal directly contradictory to shooting as much as possible when we do manage to get to the range.
The first step in the right direction, of course, is to bring more than one rifle so they can be rotated during the session, allowing hot barrels to cool. They’ll cool down quicker when the action’s open (as it must be on most ranges anyway) with the rifle standing upright in the shade. The hot air inside the barrel rises due to convection, sucking cooler air from the chamber through the bore.
However, this method only cools barrels reasonably quickly up to about 60 degrees. Above that and barrels stay hot a long time. Below the Mason-Dixon Line, temperatures often rise above 60 even in January, and even in Montana, a typical late July morning often hits 60 pretty darn early.
All sorts of solutions have been used to cool barrels quicker on hot days. One is a small rubber tube connected to a fairly large cylinder of compressed air or carbon dioxide, or a battery-powered air compressor. Stick the tube in the rifle’s chamber, then open the valve or turn on the compressor. This does cool a barrel down quicker than just letting the rifle sit (and CO2 cools quicker than plain air), but has always seemed a little complicated to me, especially when there’s more than one barrel to cool.
On moderately warm days, draping a damp towel over a hot barrel speeds up cooling appreciably, and several towels aren’t as much hassle to carry around as several air cylinders or compressors. If rifles must be left upright in a rack, a requirement on many ranges, the towel can be spirally wrapped around the barrel.
During hot weather we can wear cooler clothes, but our
rifle barrels often need some cooling help as well.
Dripping cold water on hot barrels doesn’t do
them any harm, and cools them very quickly.
On really hot days I prefer the direct approach, bringing along at least a couple of gallons of cold water to pour over barrels. This works quickest on free-floated barrels, but does cool even tightly-bedded barrels. I’ve never found it to have an effect on accuracy, whether in the short or long term, and it sure speeds things up when a lot of shooting must be done. The most effective method, I’ve found, is to tilt the muzzle downward at a steep enough angle that the water runs along the barrel for a ways.
The only real problem I’ve run into is water trapped between blued barrels and wood stocks. This can cause rust if the barrel isn’t oiled or treated with a longer-lasting preventative such as Gun Shield. The barrel channel can also soak up some water, but all of mine have either been coated in modern spar varnish (a combination or urethane and organic oil) or have a thin layer of epoxy bedding compound. If the steel and stock on your rifle isn’t protected, the barreled action should be removed from the stock when you return home and wipe everything down.
But on a typical modern rifle with a stainless-steel barrel free-floated in a synthetic stock, there’s no problem. Well, except for injection-molded stocks with the typical “bulkheads” inside the hollow fore-end. I’ve found it advisable to hold these rifles muzzle-down and jiggle ’em afterward, to allow as much water to run out of the fore-end as possible. Otherwise the next shot results in almost as much flying water as a wet Labrador, though a cool spray is sometimes welcome on a hot day.
Even the coating on the outside of the barrel can help. There are a bunch of metal coatings on the market, but the popular Cerakote was originally developed as a heat-transfer coating for radiators, engines and any other metal machines that get hot during use. It also allows rifle barrels to cool more quickly.
All of these techniques result in more shooting during the limited range sessions many of us have these days, allowing us to test more of our handloads.