Is Chris Long (Techshooter) still about?

[Dusty Stevens]

Hey ive used the best velocity transducers and magnetic induction transducers known to the world with the best dataloggers and trend viewers ever made to try to engineer a tune and still i work up my loads in the moment on paper. There is no substitute for actually shooting no matter how much info you compile even with a building full of the best vibration engineers in the world interpreting said data. And like everybody else that has had actual success in shooting and then had a lightbulb pop up above their head it was kept quiet to not have to argue with some anonymous rocket scientist telling us how it wont work. Theres a ton of very smart people in the shooting world that know how to compile and interpret data- quite a few on here actually. Lots to learn here if you can read between the lines

 

[PhilKeil]

Hey ive used the best velocity transducers and magnetic induction transducers known to the world with the best dataloggers and trend viewers ever made to try to engineer a tune and still i work up my loads in the moment on paper. There is no substitute for actually shooting no matter how much info you compile even with a building full of the best vibration engineers in the world interpreting said data. And like everybody else that has had actual success in shooting and then had a lightbulb pop up above their head it was kept quiet to not have to argue with some anonymous rocket scientist telling us how it wont work. Theres a ton of very smart people in the shooting world that know how to compile and interpret data- quite a few on here actually. Lots to learn here if you can read between the lines

Well said sir

 

[normmatzen]

Someone above mentioned finite element analysis. Anyone remember Varmint Al? He has (still, I think) web site that has some excellent work on resonances in a barrel along with FIA including the stock, bolt and scope!. I would say Al's work was a bit more than arm waving.
Whatch out for otherwise smart folks that point all their effort into a very narrow area and think their discoveries apply to everyone. Wrong!

 

[6ShotsOr5?]

Someone above mentioned finite element analysis. Anyone remember Varmint Al? He has (still, I think) web site that has some excellent work on resonances in a barrel along with FIA including the stock, bolt and scope!. I would say Al's work was a bit more than arm waving.
Whatch out for otherwise smart folks that point all their effort into a very narrow area and think their discoveries apply to everyone. Wrong!

Looks interesting! https://www.varmintal.com/atune.htm

 

[rammac]

I know nothing about the OP but I seriously doubt he's a qualified physicist. If he were then he'd understand how to research barrel harmonics papers from the DTIC or acedemic sources. There have been many papers done about harmonics and the very basics of ballistics theory includes studies of shockwaves through metals.

If you want to read some easily available information about barrel harmonics along with the supporting documentation then buy a copy of "Rifle Accuracy Facts" by Harold R. Vaughn and read chapter 4. Another very informative acedemic study of harmonics and shockware theory pertaining to ballistics is in the book "Ballistics Theory and Design of Guns and Ammunition" by Donald E. Carlucci and Sidney S. Jacobson (third edition currently).

I suspect that the OBT/ OCW theories aren't scientifically exact but they seem to have helped an awful lot of people find good loads quicker than if they'd have just guessed.

 

[hpshooter]

"BTW, I read a paper written by 2 college students on their Master thesis on the theory and experiment of the response of longitudinal waves on rifle barrel to bullet travel but I lost that AIAA paper."

I believe that paper is on line but cannot find it now.

 

[riflewoman]

For those who don’t know Geoffrey is, or was, a well respected barrel maker in Scotland. So he’s not from academia.

 

[DirtySteve]

For those who don’t know Geoffrey is, or was, a well respected barrel maker in Scotland. So he’s not from academia.

Border Barrels???

 

[riflewoman]

That said, there’s enough going on in rifle barrel dynamics that (I believe) cannot be adequately modeled in current PC based software. And since most of the “mainframe” engineering modeling softwares are even cruder, ( mostly due to being abandoned in favor of PC ) there’s not much hope there.

so you buy a barrel and shoot components trying to get the best groups possible. Who knows, you might get lucky and find a really good one.

 

[riflewoman]

Border Barrels???

I think so.

 

[6ShotsOr5?]

After reading Varmint Al’s FEA and Techshooter Chris’ OBT paper in the last few days, here is my big picture summary of what I think they said — coming from a rookie not qualified to agree or disagree:

1. Following the firing event, a rifle muzzle moves vertically up and down and even a little bit laterally back and forth in a complex path that changes not only the vertical muzzle location but also the elevation angle of the muzzle. If all the variables are kept constant, these motion paths could be very nearly the same from shot to shot, but a lot of things like different holds on the rifle can affect the vibrations. ...Varmint Al
2. Tuners can move the Mode 2 node closer to the end of the barrel and usually will reduce the magnitude of the vibrations but will not prevent angular oscillations (muzzle alternatively pointing up and down) even if the node could be moved all the way to the muzzle. Tuners don’t work like most people think. Even an out-of-tune tuner helps. ...Varmint Al
3. A shock wave travels up and down a barrel after the firing event causing multiple different effects. One effect that seems important is alternating radial constriction and relaxation. More shot dispersion occurs if the bullet exits when the muzzle is radially relaxed as opposed to when the muzzle is more constricted. The good exit times (constrictions) and bad exit times (relaxations) can be calculated within a few percent % using Quickload, and loads and barrel lengths that result in OBT (Optimal Barrel Time) can be selected to improve shot precision. ...Techshooter Chris

One thought about what Al said about out-of-tune tuners. This sounds like it could be part of the reason many people observe tighter groups when using suppressors.

 

[riflewoman]

Just adding the mass of the tuner will slow down the velocity of the oscillations at the muzzle. And I firmly believe it is the velocity of the vibrations at the muzzle that cause the most dispersion.

 

[kelbro]

I'm not sure why people think the barrel only oscillates straight up and down. Maybe it's because it is easier to show the sine wave on paper going up and down.

 

[wbm]

There is no substitute for actually shooting no matter how much info you compile even with a building full of the best vibration engineers in the world interpreting said data.

Watch it! Some "BB Stacker" will probably disagree. Then there will be pages of pompous bs and bloviation.

 

[rammac]

For those who don’t know Geoffrey is, or was, a well respected barrel maker in Scotland. So he’s not from academia.

That explains why I felt that the OP wasn't formally trained on ballistics, he sounds like a nuts and bolts kind of guy that has learned his trade through doing rather than an academic education.

I'm old enough to recognize that unfortunately some of the old guys that learned by the seat of their pants will pick up bad information and they just seem to be stuck in their thinking, it's hard to get some of them to open their mind and accept a different point of view.

 

[rardoin]

I don’t know guys/gals.... I have no trouble with Geoff’s questions and challenges of the OBT theory. Remember, the earth was flat for a couple of thousand years until it wasn’t. Men of science were nearly put to death for presenting alternative theories challenging that perhaps the earth was a sphere. See his query as an opportunity to learn. I do.

 

[BCBRAD]

I'm not sure why people think the barrel only oscillates straight up and down. Maybe it's because it is easier to show the sine wave on paper going up and down.

Easy way to explain the deviation from the x axis, a 1/2 node is as far away from the x axis as possible, you can get a good load but it will be finicky to any inputs.

 

[normmatzen]

Geofrey was the owner of Border Barrels till he sold out.
Geoffrey has a pHd and is a ballistics expert . He has built some remarkable instrumentation that can aid in ballistics tests.
His interest is primarily small bore (.22) and doesn't especially like center fire or work on the physics of them.

 

[6ShotsOr5?]

I have been trying to get more information about the Optimum Barrel Time theory that Chris Long invented back in 2016. The paper on his website is questionable in a number of respects and I have tried to get in touch with him, but no response. The last time the website was updated was also back in 2016, and the last time he posted on this forum was in 2016, so perhaps he just lost interest or he not with us any more. Anybody know....?

The last time @techshooter signed in to AccurateShooter was June 5, 2019.

 

[243Mendoza]

... Another very informative acedemic study of harmonics and shockware theory pertaining to ballistics is in the book "Ballistics Theory and Design of Guns and Ammunition" by Donald E. Carlucci and Sidney S. Jacobson (third edition currently).
...

https://www.amazon.com/dp/113805531X/?tag=accuratescom-20

A little expensive. Too bad since it seems to be the most recent book on internal ballistics.