Gene Beggs
Active member
Guys, we are getting too hung up on density altitude (DA)
Yes, it is real and can be accurately determined; and yes, it affects the tune of our rifles, but DA alone, cannot be used to get the rifle in tune. Only the rifle, at a given time and place, can tell us what it needs.
Once 'in tune' the shooter makes absolutely no changes to the load or seating depth. Changes in DA tell us which way to move the tuner and how much. If DA goes up, turn the tuner IN. This in effect, shortens the barrel, raising the frequency of vibration. With my tuner, an increase in DA of 500 feet requires a quarter turn in.
If you have no way of detemining DA or just don't want to fool with it, that's okay, the rifle will tell you when it needs an adjustment to the tuner. If a bullet hole of verticle creeps in and cannot be explained by wind or mirage conditions, the rifle is telling you to turn the tuner in a quarter turn. Pretty simple; huh? And that's really all there is to it. " Oh,,,but what if my tuner weighs more than yours or what if it has a different thread? you ask. Not to worry!
When I was a kid, I took steel guitar lessons. At the time, I could have never known that what I was learning would come in handy fifty years later when trying to figure out barrel vibration control on a benchrest rifle.
A behind-the-muzzle tuner works like the steel used to play a guitar. Place the steel/tuner on the string/barrel and move it fore and aft; the frequency rises and falls. It does not matter whether the steel weighs 3 ounces or twelve; the result is the same. This I discovered while experimenting with early tuner designs.
Through trial and error, I found that 28 threads per inch was perfect for my tuners. In one revolution, the tuner moves .036, which is the range between nodes. Adjustments are determined by clock position. Each of the collars is precisely drilled in four places, at ninety degree intervals. One of the holes is marked to identify it as the master. With the use of two small Tommy bars, the collars are loosened, repositioned and tightened. The shooter places the master at 12, 3, 6 or 9 o'clock. One of these four positions will put the rifle perfectly in tune anytime, anywhere!
Unless someone else wants to step up to the plate and take the heat, I will accept responsibility for introducing the benchrest world to density altitude. Maybe I have been guilty of overemphasizing it. The bottom line is, listen to what the rifle is telling you. My tuner has only four positions, 12, 3, 6 and 9 o'clock. Regardless of where it is set to begin with, if the rifle is out of tune that leaves only three choices.
When everyone discovers how simple it is to keep a rifle in tune with a tuner, chasing the load will be a thing of the past. "OH, but what if the wind is blowing so hard I can't tell whether the rifle is in tune or not?" you ask.
If conditions are that bad, it makes little or no difference whether the rifle is in tune or not. During those times, you just do your best to stay on paper, or do as Bob Brackney has been known to do. I'll never forget the time we were fighting the wind, rain and cold out at the Ben Avery Range in Phoenix. Bob finally said, "I'm declaring victory and leaving."
Later,
Gene Beggs
Yes, it is real and can be accurately determined; and yes, it affects the tune of our rifles, but DA alone, cannot be used to get the rifle in tune. Only the rifle, at a given time and place, can tell us what it needs.
Once 'in tune' the shooter makes absolutely no changes to the load or seating depth. Changes in DA tell us which way to move the tuner and how much. If DA goes up, turn the tuner IN. This in effect, shortens the barrel, raising the frequency of vibration. With my tuner, an increase in DA of 500 feet requires a quarter turn in.
If you have no way of detemining DA or just don't want to fool with it, that's okay, the rifle will tell you when it needs an adjustment to the tuner. If a bullet hole of verticle creeps in and cannot be explained by wind or mirage conditions, the rifle is telling you to turn the tuner in a quarter turn. Pretty simple; huh? And that's really all there is to it. " Oh,,,but what if my tuner weighs more than yours or what if it has a different thread? you ask. Not to worry!
When I was a kid, I took steel guitar lessons. At the time, I could have never known that what I was learning would come in handy fifty years later when trying to figure out barrel vibration control on a benchrest rifle.
A behind-the-muzzle tuner works like the steel used to play a guitar. Place the steel/tuner on the string/barrel and move it fore and aft; the frequency rises and falls. It does not matter whether the steel weighs 3 ounces or twelve; the result is the same. This I discovered while experimenting with early tuner designs.
Through trial and error, I found that 28 threads per inch was perfect for my tuners. In one revolution, the tuner moves .036, which is the range between nodes. Adjustments are determined by clock position. Each of the collars is precisely drilled in four places, at ninety degree intervals. One of the holes is marked to identify it as the master. With the use of two small Tommy bars, the collars are loosened, repositioned and tightened. The shooter places the master at 12, 3, 6 or 9 o'clock. One of these four positions will put the rifle perfectly in tune anytime, anywhere!
Unless someone else wants to step up to the plate and take the heat, I will accept responsibility for introducing the benchrest world to density altitude. Maybe I have been guilty of overemphasizing it. The bottom line is, listen to what the rifle is telling you. My tuner has only four positions, 12, 3, 6 and 9 o'clock. Regardless of where it is set to begin with, if the rifle is out of tune that leaves only three choices.
When everyone discovers how simple it is to keep a rifle in tune with a tuner, chasing the load will be a thing of the past. "OH, but what if the wind is blowing so hard I can't tell whether the rifle is in tune or not?" you ask.
If conditions are that bad, it makes little or no difference whether the rifle is in tune or not. During those times, you just do your best to stay on paper, or do as Bob Brackney has been known to do. I'll never forget the time we were fighting the wind, rain and cold out at the Ben Avery Range in Phoenix. Bob finally said, "I'm declaring victory and leaving."
Later,
Gene Beggs
