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Old 01-19-2017, 12:12 PM
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Barrel time



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Folks are misconstruing pressure with barrel time. Pressure and the start of recoil results in forced deformation. "Where the barrel is pointing"
Barrel time is timing from point A to Point B. Think humidity and burn rate for barrel time. All this is right on varmint al's site, the most comprehensive publication on why these rifles work the way they do.
When I shared with vibe my observations of barrel time and first posted here on rimfire central vibe and others agreed with my assessment..marty

Ps; there has been more discoverable info posted right here on tuning, ammo selection than all other sites combined..
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Old 01-19-2017, 01:22 PM
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Marty, I'll give you credit for stating what I too believe is the most important aspect of tuning and what's going on, with your post above...but I don't recall you ever stating anything about forced deformation until of late. Either way, kudos! Maybe you did, but it's really hard to read your postings and gibberish more often than not. Your post above is concise and to the point...of being mostly coherent.

That said, vibration and natural frequency still matter and that vibration begins before ignition or forced deformation occurs. Also, I don't think we'll ever agree about tuned vs. made to shoot. All I ever want is a rifle that I can make shoot..consistently and repeatably. I don't care if it's tuned or simply made to shoot.

I have been watching you test small weight differences of late. Try smaller differences. Maybe even with something as simple as a single wrap of electrical tape, at a time.
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Old 01-19-2017, 04:54 PM
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Mike, I believe a 4.0 oz tuner is what's needed with weights or bloops starting around 6 grams thru 14 grams. I think the single biggest problem I'm having right now is the 1/8 Moa scope, I believe rimfire br shooters need a 1/12 inch maybe a 1/16 inch...marty
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Old 01-19-2017, 04:59 PM
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Mike, varmint al thought a stable high frequency vibration formed always was unlikely on a 24.275 length barrel, just wasn't enough time. The shortest barrel I have is 25.750 and longest is 27.250. To date no one knows if either lengths give enough time. Marty
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Old 01-19-2017, 06:38 PM
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Quote:
Originally Posted by earnest View Post
Mike, varmint al thought a stable high frequency vibration formed always was unlikely on a 24.275 length barrel, just wasn't enough time. The shortest barrel I have is 25.750 and longest is 27.250. To date no one knows if either lengths give enough time. Marty
Are you saying that you don't believe an anti-node has time to reach the muzzle before bullet exit? I don't think the math will agree.
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Old 01-24-2017, 05:44 PM
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been busy, folks need to read this...marty
calculate and they did seem to answer some of the questions. From these FEA dynamic pressure calculations, it appears that the recoil and forced deformations are much more important than the natural vibration modes in determining where a barrel is pointing when the bullet exits the muzzle. Then after the bullet exits the muzzle, the rifle barrel vibrates in its various natural frequencies and mode shapes. Put another way, consider a guitar string being plucked. One pulls the string into a position (forced position) then releases it and the string vibrates at is natural frequency. The recoil and bullet motions "pulls" the rifle barrel to a new shape and once the bullet leaves the barrel, then the barrel vibrates. However, the addition of the scope to the model has shown some small high frequency vibrations superimposed on the forced deformations, both of which, slightly alter where the muzzle points
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Old 01-24-2017, 05:46 PM
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longer barrels?
CONCLUSION.... Maybe the "consensus" was that a rifle barrel vibrated in one or more of the mode shapes when fired. That was because the mode shapes and frequencies were easy to calculate and they did seem to answer some of the questions. From these FEA dynamic pressure calculations, it appears that the recoil and forced deformations are much more important than the natural vibration modes in determining where a barrel is pointing when the bullet exits the muzzle. Then after the bullet exits the muzzle, the rifle barrel vibrates in its various natural frequencies and mode shapes. Put another way, consider a guitar string being plucked. One pulls the string into a position (forced position) then releases it and the string vibrates at is natural frequency. The recoil and bullet motions "pulls" the rifle barrel to a new shape and once the bullet leaves the barrel, then the barrel vibrates. However, the addition of the scope to the model has shown some small high frequency vibrations superimposed on the forced deformations, both of which, slightly alter where the muzzle points before the bullet exits. For lowering the amplitude of the high frequency vibrations, it appears that even an "out of tune" tuner is better than no tuner at all.
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Old 01-25-2017, 12:53 PM
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I posted this almost 2 years ago, depicted is shift in poi caused by forced deformation. I knew then no one understood tuning/ammo selection..marty
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Old 01-25-2017, 01:25 PM
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my bet a few folks in the future will be crowing about forced deformation and ammo selection..marty
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Old 01-25-2017, 01:31 PM
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next week i'll replace the tuner on this 10x action with a shaved tuner.
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Old 02-03-2017, 12:33 PM
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10x action-reverse taper, all different profiles react differently to forced deformation.
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Old 02-03-2017, 12:34 PM
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location is as important as group size.
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Old 02-03-2017, 12:36 PM
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I'm not surprised.
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Old 02-03-2017, 12:38 PM
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or which will perform slightly better.
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Old 02-03-2017, 12:39 PM
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row 1 thru 5 tuner only- rows 6 thru 25--10 gram bloop
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