Slo-mo barrel harmonics video

[BergerFan222]

This would be a great study for a university physics or eng/phys dept looking for a project - since they'll have the equipment needed to capture the event.

Most engineering departments focus on funded projects, and bringing a firearm to Campus is strictly forbidden almost universally. You'd probably need a seven figure grant to get some exemption from that rule, and I still would not bet on it.

It would be easier for the project to be done off campus at an existing range, but then you have the challenge of getting the needed equipment to capture the event to the range. The systems are not usually designed for portability. It can be done though, but who is paying for it?

Finally, using high speed tri-axial accelerometers attached to the barrel can quantify its motion much more accurately than most high speed videos available in mechanical engineering departments. Casual shooters may prefer to "see" what is happening in a video, but mechanical engineers have greater appreciation for accurate graphs of barrel acceleration, velocity, and position vs. time. The instrumentation here is much less expensive also, and in many cases easier to get to a range.

You might try a search for something like high speed acceleration measurements of rifle barrels.

 

[BergerFan222]

Relevant links:

Using barrel vibrations to tune a barrel

https://www.shootingsoftware.com/barrel.htm

 

[scott2345]

Thanks BergerFan222. I may not have read close enough to see if this is explained, but I wonder if the barrel whip wave we see here isn't a simple 2D wave but actually more of a complex corkscrew action. With the bullet spinning around in the rifling, shouldn't you see forces in all directions?

 

[J E Custom]

Relevant links:

Using barrel vibrations to tune a barrel

https://www.shootingsoftware.com/barrel.htm

Thanks BergerFan 222.

The links were very informative and confirmed most of my experiences in technical terms with good charts and graphs.

I have these on My web site under Gunsmithing if in the future anyone wants to refer to them.

http://jecustom.com/index.php?pg=Home


J E CUSTOM

 

[Jay Kyle]

Most engineering departments focus on funded projects, and bringing a firearm to Campus is strictly forbidden almost universally. You'd probably need a seven figure grant to get some exemption from that rule, and I still would not bet on it....

True - a top-down approach would be better - for example military funded schools - but those would likely have a focused curriculum that may not have time for smaller extra-curricular projects such as this.... it was a thought.


However! the articles you brought are insightful. The first - Using Barrel vibrations to tune a barrel - does support Brownings BOSS technology (et.al)

The learnings I take away from both are:

• A barrel with a BOSS like tune-able weight on the end provides a mechanism to tune the 'whip' to coincide bullet exit and a common point in the whip cycle
• An experiment of relieving the gas pressure - before the bullet exits the barrel, to relieve muzzle gas wash, in conjunction with a barrel tuner, would be interesting.
• Barrels with decreased diameter toward the muzzle can contribute to secondary pressure rise, in the presence of other influential factors such as too-slow of a powder.
• Lastly, I thought it would be interesting to understand the complete motion of the all of barrel during the vibration event, but in reality it's the influence on accuracy that seems to be the most sought after information.

..sometimes I wish I was back in school.

 

[clambdin]

Interesting thread ! How about the effects of full length bedding of the barrel such as Melvin Forbes does with his guns and they seem to shoot well..I have rifles that are floated and a few are bedded full length I always wondered what the full length bedded barrels would shoot like if they were floated..

 

[hemiford]

This might help, it might not.

Speaking in generalities, when you have an oscillating mechanical
system, more mass decreases the oscillating frequency.
It would oscillate forever without dampening, so for our purposes
(and most practical purposes) dampening is the key.
A heavier steel barrel will help because it has some inherent damping,
but also it won't bend (whip) as easily at any frequency.

Imagine if the barrel were made of lead, it would not vibrate for long.
This is dampening.
Or if the barrel were dipped in road tar 1-inch thick, it would not
vibrate for long. Accuracy with ANY load would then be more consistent.

Sure, there is only so much we can do. Understanding what does what
will help. J E CUSTOM is absolutely correct when he says heavier rifles
will have the edge in every way except "carriability" !

 

[Mikecr]

There is also balance and recoil(actual). Heavier barrel means adding weight to the butt stock, and the system weight jumps dramatically, and it might not shoot a bit better. It's a risk.
A rest is a big part of the tune. Fill an extra bag with kitty litter, and shoot a gun from sand bag to this for comparison. All the barrel notions(about it's importance) can go right out the window with this. Then you have a mountain of internal ballistic influences with various loads that complicate conclusions, causing failed tests.

There is a whole system to our shooting system.
If I were to follow the work/answers of anyone today(about this) it would be Browning behind their BOSS system. This, including both their rubber bedding and tuner as combined.

 

[engineer40]

If not, it seems like the wrong approach to free float a barrel. Seems like you would want to lock it in and reduce movement wherever possible. Of course, weight is an issue, and most people want a lightweight barrel and perhaps this is the only reasonable approach for a shoulder fired rifle.

I guess what I'm thinking/realizing is that a free floating barrel may not be a performance enhancing feature but rather a compromise. Are we only free floating because we realize "oh crap, that thin barrel is going to bend/whip when I shoot it and if it hits the stock that's going to mess up my shot"?

My most accurate rifle is not free floated and has a thin barrel. There are a few things about the rifle that I would like to change or upgrade but I have not. I don't actually understand why it shoots a particular load so well and I'm scared to change a single thing about the rifle for fear of potentially changing the harmonics.

Free floating is just the most popular way today of keeping harmonics consistently predictable. A certain era not long ago it was popular to put thin strips of cork under the barrels.

I think the main reason free floating has risen to be the most popular way of getting consistent harmonics is to avoid POI shifts when shooting off hand vs bipod vs off bags etc. Meaning, the forearm part of the stock isn't affecting the POI.