R
Ramsh00ter
Guest
After reading the thread "keeping gun in tune", I was very impressed with Gene Beggs and Jim Bordens discussion. It go me to thinking about what the air inside the barrel was doing as the barrel heated up?
My logic (coming from a transplanted Arkie, prob pretty scary) tells me the air is heating up in perportion to the heat of the barrel? As that air heats and expands, it has to move. If indeed the air is getting hotter, it will be less dense.
So to see if we could tell if the air was actually moving in the barrel as it is heated, I set up the following experiment.
First let me say, I do not have a clue as to what this means in terms of tune.
In elementry school science we learned the a flame will travel towards an oxigen source. My thought was to place tip of a candels flame just in front of the rifles crown and photograph the flames direction. By leaving the bolt closed, I believed that the air would heat up in the barrel and flow toward the flame and the flame would lean toward the muzzle of the rifle.
PS, never forget move the candle before shooting, it blows hot wax all over your rifle, duh. If nothing else, I learned that from this experiment, lol.
All of these photos were taken with the bolt closed so that if the air is moving, it could only go out. It was kind of funny, my son had to keep reminding me not to open the bolt. After many years of being in the habit of opening the bolt immediatedly after firing, I had a hell of time not reaching for the bolt after each shot. A good habit, but one that messed this experiment up 4 or 5 times.
I did not shoot these rounds for group, as I had the exhaust fans in the tunnel turned off so that we could keep air movement to a minimum. In the tunnel, after 5 or 6 shots without the fans, it is next to impossible to have a sharp view of the target.
I started this morning with a clean cold barrel, fired 10 shots within a 7 minute time period to simulate a match.
Temperature in the tunnel was 66.1 degrees, 39% humidity at the start.
After the 10 shots, the barrel temp had risen to 85 degrees, room temperature was 67.1 degrees, 35% humidity.
The gun was then cleaned and alowed to cool down for 30 minuts.
The 1st thru 3rd shots were taken with the barrel at 85 degrees, room temp 67.9 degrees, 36.1% humidity.
The 4th to 7th shots were take with the barrel at 95 degrees, room temp 68 degrees, 35% humidity.
The 8th and 10th shots were taken with the barrel at 104 degrees, room temp 69 degrees, 36% humidity.
The 11th to 14th shots were taken with the barrel at 104 degrees, room temp 70 degrees, 35% humidity.
I went on to take 6 more shots to heat the barrel up to 110 degrees, room temp 70.6 degrees, 36% humidity.
As you can see, the tip of the flame is leaning closer to the muzzle as the barrel gets hotter. This tells me the air is expanding in the barrel and moving out? Not as much as I expected, but it is moving.
Again, I have no idea how this affects the tune of the rifle, just thought it would be interesting to do.
Randy Tidwell
My logic (coming from a transplanted Arkie, prob pretty scary) tells me the air is heating up in perportion to the heat of the barrel? As that air heats and expands, it has to move. If indeed the air is getting hotter, it will be less dense.
So to see if we could tell if the air was actually moving in the barrel as it is heated, I set up the following experiment.
First let me say, I do not have a clue as to what this means in terms of tune.
In elementry school science we learned the a flame will travel towards an oxigen source. My thought was to place tip of a candels flame just in front of the rifles crown and photograph the flames direction. By leaving the bolt closed, I believed that the air would heat up in the barrel and flow toward the flame and the flame would lean toward the muzzle of the rifle.
PS, never forget move the candle before shooting, it blows hot wax all over your rifle, duh. If nothing else, I learned that from this experiment, lol.
All of these photos were taken with the bolt closed so that if the air is moving, it could only go out. It was kind of funny, my son had to keep reminding me not to open the bolt. After many years of being in the habit of opening the bolt immediatedly after firing, I had a hell of time not reaching for the bolt after each shot. A good habit, but one that messed this experiment up 4 or 5 times.
I did not shoot these rounds for group, as I had the exhaust fans in the tunnel turned off so that we could keep air movement to a minimum. In the tunnel, after 5 or 6 shots without the fans, it is next to impossible to have a sharp view of the target.
I started this morning with a clean cold barrel, fired 10 shots within a 7 minute time period to simulate a match.
Temperature in the tunnel was 66.1 degrees, 39% humidity at the start.
After the 10 shots, the barrel temp had risen to 85 degrees, room temperature was 67.1 degrees, 35% humidity.
The gun was then cleaned and alowed to cool down for 30 minuts.
The 1st thru 3rd shots were taken with the barrel at 85 degrees, room temp 67.9 degrees, 36.1% humidity.
The 4th to 7th shots were take with the barrel at 95 degrees, room temp 68 degrees, 35% humidity.
The 8th and 10th shots were taken with the barrel at 104 degrees, room temp 69 degrees, 36% humidity.
The 11th to 14th shots were taken with the barrel at 104 degrees, room temp 70 degrees, 35% humidity.
I went on to take 6 more shots to heat the barrel up to 110 degrees, room temp 70.6 degrees, 36% humidity.
As you can see, the tip of the flame is leaning closer to the muzzle as the barrel gets hotter. This tells me the air is expanding in the barrel and moving out? Not as much as I expected, but it is moving.
Again, I have no idea how this affects the tune of the rifle, just thought it would be interesting to do.
Randy Tidwell
