Barrel Harmonics and such.

Kroozer

Down the page here there is an absolutely tremendouse expalnation of Ballistic Coeficiants and such. That thread led me to thinking that I just don't know as much as maybe I should about the subject.

One thing among many came to mind. Barrel Harmonics.

Correct me if I'm wrong. Barrel Harmonics is the whip your barrel makes as the bullet passes down it's length.

Barrel Harmonics is effected by the barrel contour of your firearm, the length of the barrel, bullet shape, weight, length, etc.. . .if there is an ect..

Is there any KISS solution to figuring out what's best for "your gun" in advance of running countless different rounds through the barrel? Maybe not a complete answer for sure, but maybe a good head start in the right direction?

One last thing. Have any of you had experience with the rubber donut thingy "they" sell that slides/goes over the barrel, and is place by the owner at a spot, up or down the barrel, that is best for that gun? Please let me know all of what's going on with that device.

Thanks in advance.

iwannausername

Check out the Browning BOSS system....

rsnyder55

Another possibility is to cut the end of your barrel 1/2" at a time until you get the tightest group.

Kroozer

Thankyou for your replies thus far.

I don't want to alter the gun however. I want the gun to tell me it's "secret" potential.

perry shooter

Hello the boss system makes the rifle "TUNEABLE" but you can do the same buy tuning your load Start with light load and work up at one point the groups will get smaller and then get larger as you increase the velocity go with the load with the smalles group a deer or target will not know the differance in 50 to 100 FEET PER SECOND. There is more to it but simple way of thinking is you want the bullet to be leaving the barrel at the end of a CYCLE of the whip.

jack85

Unfortunately there is no easy way to predict how a barrel will whip, or for that matter how much the whip will affect group size. The amount or direction of whip will depend on barrel profile, stock configuration, bedding, screw tension, caliber, bullet mass, load etc. In general -- long thin barrels rarely perform as well as a short stiff barrels.

Bert H.

Barrel harmonics is not really "whip", but is best described as oscillation (or vibration) induced by all of the variants you mention, plus the C.U.P. of the load, the overall weight and wall thickness of the barrel, the steel alloy used, the twist rate of the rifling, the exact dimension of the chamber, the type of stock and how the action and barrel are mounted in the stock, temperature of the barrel, and a few other vaiables that I am undoubtedly forgetting to mention.

There is no simple solution to finding which load is the best possible for an individual barrel other than trying lots of different loads. The BOSS system used by Browning and Winchester allows you to tweak the barrel for a specific load versus tweaking your load to the barrel.

JustC

OK, I'll give this one a run..

first, shorter equals more rigid and longer equals less rigid (given an identical contour). As a barrel gets longer, it needs a much thicker profile to remain as rigid as a shorter and thinner barrel. This is the result of gravity pulling down on the longer barrel creating a greater force than it does on the shorter barrel. You can see this for yourself by holding a short 2x4 in you hand as if it were the action and then holding a much longer 2x4 the same way. You can feel the increased pressures which are applied to your hand (receiver ring and threads). In order to overcome that gravity, the dia needs to be larger to better support itself over distance and some bedding under the the first few inches takes a lot of the pressure off the receiver ring and threads.

action symetry is very important as well. If your action is untrue, accuracy suffers. BOTH bolt lugs need to make a SOLID engagement into the lug seats so as to apply a straight back pressure under ignition rather than have the bolt flex and apply forces at different times as one lug engages before the other. Also, if you want it down to miniscule variables, one would actually take and drill a hole on the left side of the receiver opposite the one on the right which is a gas venting design feature as well as drilling holes in the underside of the action to mirror the scope base screw holes on the top side. The theory being that the action is now identical in shape and density on both sides and top and bottom.

Your stock if flimsy is a degrador of accuracy. A stock needs to be rigid as well as having bedding applied to the action area to eliminate the gaps, which change or damage a harmonic frequency. If the stock isn't vibrating the same as the barrled action, you have an arresting action taking place.

Time that the bullet is in the barrel is also a factor as it actually causes the wave effect as it passes down the bore, much more so on sporter barrels. This is why you can't just take any acceptable powder, and find the same MV as another powder you used and expect it to be the accuracy load for the new powder. The pressure curve, the time it takes to reach peak, and the time the bullet is in the bore are all different between powders and bullets, so each new powder must be tested to find where it falls into a pressure curve that creates a harmonic that your rifle likes.

These are a few of things that control harmonics. Shorter barrels will have different frequencys from longer ones, but that does not mean they both won't shoot extremely accurately.

ultimately, it is trial and error when switching loads or components, but that is half the fun. You have to look at barrels in a different way,.........I liken them to the tires on your car, you buy them and use them until they are past their service life, then you replace them with new ones. Barrels are sacrificial components, they will get eroded and need replacing, no way around it.

nononsense

Kroozer,

Rather than reiterate what the others have written, I'll add some more reading material for your question.

Secrets of the Houston Warehouse

http://www.angelfire.com/ma3/max357/houston.html


COMMENTS ON LONG RANGE
BALLISTICS

by Geoffrey Kolbe

http://www.border-barrels.com/articles/art1.htm

THE MAKING OF A RIFLED BARREL.

by

Geoffrey Kolbe

http://www.border-barrels.com/articles/bmart.htm


What Makes a Rifle Barrel Accurate?
Dan Lilja

http://www.riflebarrels.com/articles/barrel_making/rifle_barrel_accurate.htm

There is a bunch of articles on Dan's website and all are worth reading.


Understanding Firearm Ballistics

http://www.shop.com/op/~Understanding_Firearm_Ballistics-*-18203379


Ladder Load Development:

http://kingfisher.0catch.com/guns/laddertest.explanation.html


Developing Accurate Loads:

http://www.frfrogspad.com/loaddev.htm


That should keep you busy for few minutes anyway. Have a good holiday!

Best.

blacarrow

Until retirement, I was the Chief Firearms Test Engineer at Browning Research & Development Division for many years. My principal job was accuracy testing, and was privileged to do about 95% of the developmental testing for the BOSS system (some also done at USRAC by Winchester technicians)(I also named the system). I fired well over 30,000 rounds of various calibers during the program. After each 3 shot group the rifle was cooled with compressed air. The size of the group was measured from center to center, and the results recorded. Speed was recorded on an Ohler chronograph.

I'd wear out your patience detailing all that was discovered during testing, but to put it in a "nutshell", each barrel exhibited unique individual characterisics, resulting in unique "harmonics". An ultra high speed photo imaging system clearly showed this to be the case. The heart of the BOSS system is the adjustable barrel weight which allows the system to "tune" the barrel, resulting in optimal accuracy. As I recall, the tightest group I ever fired was .0029 of an inch. All groups werre fired at 100 yards

I know this is out in left field and not exactly what the original inquiry asked, but thought it may prove interesting. Sorry to be so windy.

ern98

The simple answer is no; you have to figure it out for yourself. Most folks decide on what they need/want out of a given rifle for what they want to do with it. When they find a combo that works they stay with it and say good enough. That is why, IMO, deer hunters say that if they can hold 2"@100yds they are good to 300yds and thats all they really have to have, though they would like better. Large vamint hunters want and need better, like 1"@100yds, and small vamint shooters want even better still. Long range target shooter want everything that they can have. Each time you step up a level in preformance you can figure in it being more and more expensive. Also the amount of time and effort to figure out what really works goes up as well.

guntech59

Great thread, guys. You answered some questions I never even thought of asking! THANKS!!