Attenuation of vibration harmonics
I am reading that "Heavier barrels produce better inherent accuracy due to their ability to attenuate the vibration harmonics associated with a bullet passing through the rifling and exiting the muzzel of a barrel. Bert H.
So, is what Bert saying is that the barrel "shakes around" a little when the bullet starts spinning in it, and the heavier barrel counter-acts this reaction to the spin?
(For every action there is an equal and opposite reactionAnheuser Busch
more stuff ...
Then I looked up Attenuation
Attenuation ... 3. The process of weakening in intensity; diminution of virulence; as, the attenuation of virus.
I've seen barrels that looked 1.25" in diameter, for a .17 bullet. The whole set-up looks like it can hit a quarter at 300 metres.
So, is what Bert saying is that the barrel "shakes around" a little when the bullet starts spinning in it, and the heavier barrel counter-acts this reaction to the spin?
(For every action there is an equal and opposite reactionAnheuser Busch
more stuff ...
Then I looked up Attenuation
Attenuation ... 3. The process of weakening in intensity; diminution of virulence; as, the attenuation of virus.
I've seen barrels that looked 1.25" in diameter, for a .17 bullet. The whole set-up looks like it can hit a quarter at 300 metres.
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I must admit that I am unsure as to what exactly the intent of your post is[?] Are you clarifying my earlier statement, or disagreeing with it[?]
To add just a bit more information to my first mention of this phenomenon, all rifled barrels oscillate at a frequency that is determined by the pressure, velocity, and bullet weight. This oscillation (harmonic vibration) begins the instant the bullet begins its travel down the bore. In reality, it is actually a very small amount of movement, and it can be nullified by very consistent loads, and or a heavier barrel. The greater the mass of the barrel, the more it dampens (attenuates) the vibration imparted into it by the passing of the bullet.
The only people that are really concerned with minimizing this phenomenon are the competitive shooters who shoot at distances exceeding 200 yards. My Grandfather was the Oregon State Benchrest champion for 11 straight years in the 1950s to early 1960s. He passed on a LOT of his vast knowledge concerning "accurate" long-range shooting to my father and myself over the many years that he lived (he passed away in 1991 at 87 years of age). I have the rifle that he competed with (a modified Springfield 1903 with a 26.5" Douglas competition bull barrel chambered for 30-06). It is 1.05" in diameter at the muzzle, and is completely flush with the top of the receiver at the breech end. At 100 yards (off of a bench) I have fired 10-shot groups that are nothing more than a fuzzy single hole (less than .400 inches). I also inherited 2,000 LC National Match cartridge cases (dated from 1957 - 1963) several hundred of which are in their original boxes, and have only been fired one time.
Bert H.
Real Men use a SINGLE-SHOT!0 -
Excellent reading! [8D]
So the barrel "plays a note" (harmonic vibration). More great lore of firearms.
I wanted clarification. Your phrase is one I had not heard.
Thanks.0 -
From what I understand the heavier barrel us less likely to distort from heat and "whip" or flexing at discharge. Harmonics are like a sine wave for lack of a better discription. As browning mastered it with their "Boss" system which adjusts barrel harmonics by adjusting the overall legnth of the barrel and can turn a standard sporter barrel contor into a 1/2 moa shooter. the other factor is the actual load which burns at different rates shot to shot measured as extreme spread this can be 100 fps in some cartridges and less than 4 fps in cartriges like the 6 br. the varing speed of the round exiting the barrel will send a different "Wave" I've read that its the timeing of this "wave" that can bump the bullet as it exits the barrel and knock it off kilter enough th open the group or cause a flier. 0 -
It is a measurement known as "tonnage" of steel. The amount of steel surrounding the bore defines the amount of barrel vibration or "harmonic frequency" which it can dampen. However,..there is a point of diminishing returns. If a barrel is a straight tube (1.250-1.50" dia) all the way to the muzzel,..and it is finished at a length of say 30",..it will need a bedding compound placed foreward of the action,..in the barrel chamber for support of the barrel itself due to it's weight (this is what is refered to as a barrel pad) it is usually a 1-2" pad of the bedding compound which will help to support the weight of that much barrel hanging on nothing but the receiver threads. Just the weight of a barrel that heavy will cause it to droop ever so slightly due to it's long profile. There is a formula (which I don't have with me) which calculates the max dia of a barrel at a predetermined length before it starts to droop under it's own weight. This is why some of the hunter class benchrest rifles with 20-22" barrels shoot such small groups,..their short length makes them extremely rigid at that diameter. A 30" barrel would need to be almost 50% larger,..just to support it's own weight over that extra distance.
Another factor in uniforming barrel frequency is the handload. If the bullets are not loaded to near perfect tolerances,..then groups will suffer as well (goes without saying). Next and obviously is the free floating of the barrel. It must NOT make contact with anything,..even during vibration. Also,..barrel stress relief is a big part of this as well. Many barrel blanks (cheaper ones) are cut from and turned down from unstraight peices of steel. If that peice of steel is NOT stress releived,..then as the barrel heats up,..the natural properties of the steel make it try to return to it's original shape (bent),..thus your vibrational frequency will change, and groups will open up until the barrel is cooled down and returns to it's manufcatured shape,(most any factory sporter barrel on mass produced rifles shows this trait)
why chase the game when the bullet can get em from here?....
Got Balistics?0 -
quote:Originally posted by GPWEAPON
From what I understand the heavier barrel us less likely to distort from heat and "whip" or flexing at discharge. Harmonics are like a sine wave for lack of a better discription. As browning mastered it with their "Boss" system which adjusts barrel harmonics by adjusting the overall legnth of the barrel and can turn a standard sporter barrel contor into a 1/2 moa shooter. the other factor is the actual load which burns at different rates shot to shot measured as extreme spread this can be 100 fps in some cartridges and less than 4 fps in cartriges like the 6 br. the varing speed of the round exiting the barrel will send a different "Wave" I've read that its the timeing of this "wave" that can bump the bullet as it exits the barrel and knock it off kilter enough th open the group or cause a flier.
Hello GP... [^]
What you read is precisely what I am talking about, and the BOSS system used by Browning and Winchester was indeed specifically designed as a means of attentuating harmonic barrel vibration.
Bert H.
Real Men use a SINGLE-SHOT!0
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