Barrel harmonics with bullet weights.

[Steelflight]

So I know if you match things up right then harmony is reached. In terms of achieving lasting stability (shot after shot.)the answer is to throw on a heavier barrel. (Not to confuse the issue with heat sinking your shots.)

I want to know if any public knowledge has been put out there on the harmonic vibrations caused by different bullet weight as they spend that nano second blasting forward. Any direction has my thanks. If not then maybe one day I'll look into it. ( when I'm rich and bored. lol) This has more to do with 25" or longer barrels.

I'm simply curious about what the different movements would be like.

 

[Rhett Crider]

Buy Quick-Loads. Your answer to most of your question is there. To me, heavier contours reduce the amount of vibration at the muzzle but not the timing. Example, two barrels, say Bartlien 5R in 8 twist #3 and #5 in same length and in same cartridge and with same reamer. Exact same load. The #3 shoots 1 MOA, the #5 would bring it down to 3/4-1/2 MOA. My opinion.
Lighter bullets are generally faster and will change your timing at the muzzle. Bearing surface on the different bullets will effect also.
Lots of members w/ more experience here but this is how I deceive it.

Rhett

 

[J E Custom]

I is a common practice to add weight to the end of a barrel for better harmonics. the trick is to tune it to your rifle for best results. there are several ways to do this. One is to make the weight adjustable by threading and simply screw the weight in or out while shooting for best groups.

Or screw a muzzle brake on the barrel and machine a little weight off while shooting to reach the same effect, make sure that the brake is strong enough to allow some material removal by checking with the manufacture. (He should know how much it will allow).

The other way is to re crown 1/16th at a time to reach the best harmonics. This is the way many bench rest shooters achieve the best accuracy. They start with a barrel that is general a little longer than they want to end up with, and test fire at least 3 rounds each time they cut the barrel length 1/16 "th and the first time it doesn't change they consider it tuned and end the process.

There are many things that will improve harmonics (Consistency) different stock materials and muzzle brake designs will also effect harmonics. the longer the barrel the more susceptible it will be to increased harmonics. Tuning harmonics can be a good way to improve the accuracy and consistency.

J E CUSTOM

 

[BallisticsGuy]

It's called optimum barrel time and there are applications and formulas exist to estimate such things. All they're going to be are estimates and I know a few people that continuously try to find golden starting loads based on such estimates and they normally have less than stellar results without resorting to other more standard methods for load development. Rhett's instincts for deflection are good. A thicker/more rigid barrel should attenuate the magnitude of any deflection but not necessarily the wavelength (timing) provided the vibration is in a single plane. It won't be. One thing with rifle barrels that I have to hypothesize (though I feel I'm on firm ground here) because I don't have the equipment to actually measure is, there's got to be a bunch of torque loading that is involved and vibrations in the barrel aren't going to be limited to say just straight up and straight down or just 7 o'clock to 1 o'clock. Rifling pattern could even play a role in the whole schlameel. For an example, go find a whip antenna of any length and give it a flick in any single direction. It will not oscillate back and forth only but will instead describe something of a precessing oval.

This might enlighten some folks about vibration. The animations are exaggerated enough to get the point across.

 

[Rhett Crider]

Optimal Barrel Time Paper

This is much easier for me to understand.

 

[Steelflight]

Appreciate your feed back every one. Now I have a starting point. Thanks