Discussion in 'Smoothbore' started by GregLaRoche, Sep 11, 2019.
How does a barrel heating up effect accuracy with a smooth bore?
Same as a rifled gun IMO. That's if you experience any effects from heating.
I can't shoot mine fast enough to get it hot enough.
Metal when heated expands in all directions. So technically on a very warm day, doing quite a bit of shooting, the bore will become tighter, thus increasing pressure, and your shots will print noticeably higher than on a cool day.
The barrel is going to get tighter from fouling too, If you swab between shots it will keep both fouling and temperature under control.
Typically (in rifles anyway) overheating can cause warping or pressure points that can give you a moving or wandering zero. Though I haven't personally had it happen with a muzzleloader (cause I shoot slow)
Oh. I thought we were talking about smooth bores. Swabbing only knocks down the fouling. It really doesn't do much to cool down a barrel, maybe some, just not much.
Anyone had experience with accuracy getting better or worse as the barrel heats up?
One really has to know one's gun to answer that question. And I had to change my point of aim...lower, in fact. Got beat by one point on a 50 yard match on a 97° day.
As the barrel heats up the bore will get larger in diameter though not much. If you had a doughnut made of steel and you heated it a couple of hundred degrees the hole will get larger and the outside diameter will also increase. This is the principal behind shrink fitting where the outside part is heated to expand it and the inside part is cooled to contract it slightly. When pressed together and they both reach the same temperature an extremely tight fit is the result.
Did your group open up at all or were your shots only vertically higher?
There is a Silhouette match at Friendship for smoothbores. Targets are 25 to 120 yards away. It's been a while since I shot it. I think its 25 shots in 45 minutes. The barrel will get very hot. Heat mirage causes the sights to get wonky. The barrel does expand some due to the heat and a thin barrel may skew slightly if a barrel lug binds. We do wipe down the outside of the barrel with a wet rag between shots to reduce the mirage effect.
Nope..., it's very doubtful that you'll be shooting fast enough to get the barrel sooo hot that you can't grasp it. That's something us reenactors shooting blanks have experienced, and occasionally folks at "speed shooting" events at matches. Speed shooting matches have from what I've seen, been discontinued. Enough guys had the main powder charge "cook off" that folks decided that would be very bad if the cook-off happened when ramming the ball with the rammer.
It's hard to tell after the passage of time. I do remember however, that we were shooting at one of the standard NMLRA off hand 50 yd. targets. That in and of itself would be one significant variable in any weather.
A hot, sunny day will definitely heat up a barrel to where it's uncomfortable to hold. I cannot imagine ever being able to fire a smoothbore fast enough to get it even moderately hot.
On a hot day in a NSSA match, the barrel can get quite hot by the end of a relay. I haven't noticed any accuracy issues in mine.
At a skirmish last year I had the barrel of my Springfield so hot I had to put a rag through the sling swivel to load in several events as the metal was too hot to touch. I haven't noticed any deteriation in accuracy at times like that.
To the OP Dude you are thinking to hard. Give a it breath please.
Smoothies are NOT BENCH REST. I got away from that to relax.
Some people relax in different ways. For me, I’m planning to shoot in competition against some guys and gals that are really good. I want to do the best I can. If I know that on a hot day after shooting a number of shots, I need to aim a little lower, that’s important to me.
The biggest issue with the hot barrel is the change in view through the mirage caused by the heat waves coming off the barrel and distorting the sight picture. Yes, the bore will change diameter slightly due to the heat, but the build-up of the fouling is more significant but still not so much that you really need to change your point of aim.
The only way to know how your personal firearm changes in point of aim is to run through the course of fire and see how the impact moves across the target. I would speculate that the ball impact would rise as fouling built up and internal pressures increased. I normally shoot at reactive targets in the higher rate of fire competitions and all is needed is to hit he target so I hold on the bottom third of the target. I use my brush to wipe the frizzen and pan between shots. Sometimes I run a damp wad of tow down the barrel if I feel the fouling is starting to make it hard to load. That wipe takes less to do than dealing with a ball stuck in the barrel due to excessive fouling. If using a paper wrapped cartridge, I spit on the wrapped ball as I place the paper wrapped ball on the muzzle. Keeps the fouling under some slight control. Wear a glove on the hand that comes in contact with the hot barrel. A burning hand can have more of an adverse effect than the change of bore diameter from a hot barrel.
I would expect that heat distortion of the barrel from bedding, barrel band or underlug/pin fit, tension of the tang screw and localized stresss around sight dovetails etc. would have a much greater effect on accuracy than any bore diameter increase from the heat. Consider the effect of the sun heating the top half of the barrel too.
I was just looking back to my post #15 and realized that situations like that the heat has a far greater effect on me and my ability to shoot well that any heat buildup in the barrel.
When working up a load or zeroing a gun I shoot at a moderate rate and in the shade to counteract any effects of barrel heat. All the matches I shoot have to be completed in 1 relay without leaving the line so heat buildup is a fact of life and not controlable.
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