Vel vs Harmonics...

[Smokey]

Having fun reading the bbl length and annealing posts and thought I would toss this out to chew on...

Its pretty common for a gun of any caliber to shoot more accurately at lower than max speed, however, why?
This got me thinking several years back when I bought a Browning in 300WM with a BOSS system. What I found was instead of needing to try several powders, ( which I did ), I could make the gun shoot much better groups simply by changing the harmonics with the moveable weight.
So, if someone has a powder that won't shoot good groups its more likely related to bbl length because that particular powders burn rate creates poor harmonics with the bbl that gun is wearing. Changing powder will change the harmonics even if you are trying to duplicate the velocity of the inaccurate powder because of burn rate changes.
Ex - say powder X produces 2500 fps and out of a 20 in bbl it has fair to poor accuracy results - add 1 or 2 inches to that same bbl and it may/could/should change the grouping size dramatically when applying the BOSS system thought process...
So, saying "well a 20 in bbl for this caliber is good enough because the powder burn efficiency ended at say 18 in approx.", sounds good, but in theory 21 or 22 in bbl with the same load may produce much better accuracy. Does any of this matter much under most hunting conditions - probably not - may for a long range hunter though..?

[limon32]

Having fun reading the bbl length and annealing posts and thought I would toss this out to chew on...

Its pretty common for a gun of any caliber to shoot more accurately at lower than max speed, however, why?
This got me thinking several years back when I bought a Browning in 300WM with a BOSS system. What I found was instead of needing to try several powders, ( which I did ), I could make the gun shoot much better groups simply by changing the harmonics with the moveable weight.
So, if someone has a powder that won't shoot good groups its more likely related to bbl length because that particular powders burn rate creates poor harmonics with the bbl that gun is wearing. Changing powder will change the harmonics even if you are trying to duplicate the velocity of the inaccurate powder because of burn rate changes.
Ex - say powder X produces 2500 fps and out of a 20 in bbl it has fair to poor accuracy results - add 1 or 2 inches to that same bbl and it may/could/should change the grouping size dramatically when applying the BOSS system thought process...
So, saying "well a 20 in bbl for this caliber is good enough because the powder burn efficiency ended at say 18 in approx.", sounds good, but in theory 21 or 22 in bbl with the same load may produce much better accuracy. Does any of this matter much under most hunting conditions - probably not - may for a long range hunter though..?

I'm not familiar with the boss system but your thoughts on barrel harmonics are definitely interesting. I'm interested to watch the conversation this thread produces!

[alaskabliss]

This may help explain Harmonics. This guy seems pretty educated with firearms and accurate long range shooting. He has a series that takes you through a lot of information

http://youtu.be/h407yVskVeM?list=PLJ...BZi0vDCIcEPxUn

[Nitroman]

Having fun reading the bbl length and annealing posts and thought I would toss this out to chew on...

Its pretty common for a gun of any caliber to shoot more accurately at lower than max speed, however, why?
This got me thinking several years back when I bought a Browning in 300WM with a BOSS system. What I found was instead of needing to try several powders, ( which I did ), I could make the gun shoot much better groups simply by changing the harmonics with the moveable weight.
So, if someone has a powder that won't shoot good groups its more likely related to bbl length because that particular powders burn rate creates poor harmonics with the bbl that gun is wearing. Changing powder will change the harmonics even if you are trying to duplicate the velocity of the inaccurate powder because of burn rate changes.
Ex - say powder X produces 2500 fps and out of a 20 in bbl it has fair to poor accuracy results - add 1 or 2 inches to that same bbl and it may/could/should change the grouping size dramatically when applying the BOSS system thought process...
So, saying "well a 20 in bbl for this caliber is good enough because the powder burn efficiency ended at say 18 in approx.", sounds good, but in theory 21 or 22 in bbl with the same load may produce much better accuracy. Does any of this matter much under most hunting conditions - probably not - may for a long range hunter though..?

Go over to Accuratereloading.com and look into the files there on their loads for various cartridges. You can see how roughly 3/4 max will almost always give best accuracy. Once you start to get up into the pressures, the metal begins moving around, becoming more elastic. Dan Lilja has some interesting articles regarding stresses in the bolt. You can read them.

The burn rate doesn't create the harmonics, it is the bullet moving through the barrel. Yes, I know people will then say "oh it's the burn rate that moves the bullet". Whatever.

[Smokey]

Go over to Accuratereloading.com and look into the files there on their loads for various cartridges. You can see how roughly 3/4 max will almost always give best accuracy. Once you start to get up into the pressures, the metal begins moving around, becoming more elastic. Dan Lilja has some interesting articles regarding stresses in the bolt. You can read them.

The burn rate doesn't create the harmonics, it is the bullet moving through the barrel. Yes, I know people will then say "oh it's the burn rate that moves the bullet". Whatever.

Nitro, I thought the same way until I found I could take hot loads that were not very accurate and simply by adjusting the BOSS system in or out they tightened up considerably.
I don't think any of the authors or bullet makers have run a controlled test using an adjustable system to see what the results would be... When you look at a reloading manual with several powder types used the star placed beside the most accurate load for each powder type is all over the place. For some powders it was the max on the majority it is below max.I think it would be interesting to see those same tests run with an adjustable system to see if the shooter could get the accuracy they wanted at the top end of FPS consistently simply by adjustment. I have found that to be true in my few tests for sure...
Anyway it opens up the head for some serious pondering! Headed out to AZ at noon, hope to meet that outlaw gunsmith, Andy, they kicked outa Alaska a couple months ago! Thanks for the inputs sir!

[Smitty of the North]

Anything you do to change the load or gun will have an effect on accuracy, including cranking on the Boss. OR changing the barrel length. OR varying the powder charge...

When we vary the powder charge for better accuracy, we are changing the velocity and the time the bullet leaves the barrel, hopefully to a time in the vibration that allows better accuracy.

SOTN

[hodgeman]

Yep- I've got a rifle that shoots only so-so at max load...but backed off a couple of grains and it shoots bug holes with RL 17.

The BOSS was a really interesting concept but seems to have not caught on. I've only messed with one and it was easy to dial a load in. Just the opposite of what we do at the bench. Dialing the rifle for the load instead dialing the load for the rifle.

[iofthetaiga]

The BOSS was a really interesting concept but seems to have not caught on.

I suspect the reason it didn't catch on is twofold. First is that it was supposedly louder; it heard it said many times that it "was too loud".... Second is that the vast majority of the consumer market aren't inclined to experiment; they generally aren't willing/able to adjust anything. Which, ironically, makes it easy to sell them a worthless product, but often difficult to sell them a very worthwhile product. I think it's reputation for being loud was just a convenient excuse to dismiss it, by those unwilling/unable to understand the concept of how it worked.

[2jumpersplease]

I just watched some YouTube videos on the BOSS. Looks like a ported and non-ported version for folks to address recoil or noise depending on the situation. It seems like it could save a lot of cash with load development. I guess you just need to pick which parts of the system you like playing with.

[Smokey]

Well, made it back alive from Nogales, AZ on the Mexican border, and shook Andy's big mitt in Phoenix! Onry looking cuss he is!
Time to settle in for some hunting as the Mrs. and I have logged over 7200 driving miles in a month going from Niagara Falls to Tucson Az, pooped!

I have both BOSS tools for my 300wm, the ported IS very loud for sure but really softens recoil. I would NEVER shoot it without hearing protection and laying prone can be interesting when the dirt goes flying from the blast. The conventional system seems to work the same. One thing that does stand out is it adds considerable length to the gun so for some hunters that could be a negative...

[ADfields]

Glad ya made it and too bad you didn't have more time.

Yea those Boss rifles are sure long. I've shortened a lot of them, lopping 2 or 3 inches off and a new 1/2-28 thread makes them a lot better handling.

[7mmstalker]

I suspect the reason it didn't catch on is twofold. First is that it was supposedly louder; it heard it said many times that it "was too loud".... Second is that the vast majority of the consumer market aren't inclined to experiment; they generally aren't willing/able to adjust anything. Which, ironically, makes it easy to sell them a worthless product, but often difficult to sell them a very worthwhile product. I think it's reputation for being loud was just a convenient excuse to dismiss it, by those unwilling/unable to understand the concept of how it worked.

That sure is the truth!
The cost and scarcity of reloading components would be a good reason to add this to a rifle build.
I guess the look of an adjustable weight on the end of the barrel doesn't appeal to everyone.