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Joined: Dec 2005
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Campfire Outfitter
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Campfire Outfitter
Joined: Dec 2005
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Read somewhere once that a Bbl length/velocity test for 22RF was performed, and IIRC velocities began to decrease somewhere around the 32" mark.
I wonder if your Chrony sky screens were a 1/16" closer together how much would that would change velocity????
"...A man's rights rest in three boxes: the ballot box, the jury box and the cartridge box..." Frederick Douglass, 1867
( . Y . )
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Joined: Jul 2001
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Campfire Kahuna
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Campfire Kahuna
Joined: Jul 2001
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He didn't use a Chrony, he used a ProChrono, which has skyscreens a fixed distance apart, unlike the hinged Chrony.
I have tested two different ProChronos against an Oehler 35P, and while the individual shots will vary some from the Oehler, there's less than 10 fps difference in the average with 10-shot strings.
“Montana seems to me to be what a small boy would think Texas is like from hearing Texans.”
John Steinbeck
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Joined: Sep 2004
Posts: 17,386
Campfire Ranger
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Campfire Ranger
Joined: Sep 2004
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Once the powder is fully burned, any remaining barrel length is just friction slowing down the bullet.
Every barrel/bullet/powder/cartridge combination has an optimum length.
So, this makes perfect sense. In principle, I agree, but your first statement isn't quite right. After the powder is fully consumed the hot gases continue to expand and accelerate the bullet until pressure drops below the threshold required to accelerate the bullet, which I believe is below 2,000 psi in most cases (I believe MD has mentioned that it takes about 2,000 psi to engrave a bullet, which is more than the pressure necessary to accelerate the bullet once it's beyond the throat). good point.
“Live free or die. Death is not the worst of evils.” - General
John Stark.
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Joined: Oct 2008
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Campfire Tracker
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Campfire Tracker
Joined: Oct 2008
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I think I will go with Mule Deer and Phil Sharpe on this one.
They collectively represent close to 100 years of objective experience and actual testing.
But I am not about to chop down all my barrels to gain more velocity.
Last edited by Tejano; 06/27/16.
"When you disarm the people, you commence to offend them and show that you distrust them either through cowardice or lack of confidence, and both of these opinions generate hatred." Niccolo Machiavelli
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Joined: Sep 2010
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Campfire Ranger
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Campfire Ranger
Joined: Sep 2010
Posts: 19,179 |
djb,
A slight velocity increase when shortening barrels has been recorded many times before.
Phil Sharpe saw it in his experiments decades ago, when he shortened barrels an inch at a time and shot at least 10 rounds (as I recall) at each length. Obviously it has / can happen. I'm not experimenting with mine. Jerry
jwall- *** 3100 guy***
A Flat Trajectory is Never a Handicap
Speed is Trajectory's Friend !!
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Joined: Sep 2005
Posts: 7,132
Campfire Tracker
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Campfire Tracker
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Shotguns shoot faster with tighter chokes, similar to the Venturi effect. I suppose it could apply to a rifle bore with varying ID.
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Joined: Jun 2001
Posts: 32,028
Campfire 'Bwana
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Campfire 'Bwana
Joined: Jun 2001
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Screw the velocity- a few ft/sec ain't gonna kill any better or any worse. Did the accuracy change for better or worse. docking a bbl tends to increase accuracy IME. But not always.
The only true cost of having a dog is its death.
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Joined: Jun 2001
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Campfire 'Bwana
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Campfire 'Bwana
Joined: Jun 2001
Posts: 32,028 |
Screw the velocity- a few ft/sec ain't gonna kill any better or any worse. Did the accuracy change for better or worse? Docking a bbl tends to increase accuracy IME. But not always.
Years ago I had a customer come in with the same claim about his Ruger 77 in .338WM after I cut his bbl to 20 inches. So he brought me 2 more. About killed me , but the customer is always right! Why he had 3 Ruger 77 .338 tangs, I have no idea.
I have one, and it still has it's original length bbl. The '77 tang in '06, however, has a 17 inch bbl.. Long story... and for once, NOT MY FAULT!
Shoots 1.25 inch groups. Have no idea of MV, but I've killed to nearly 400 yards with it.
The only true cost of having a dog is its death.
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Campfire Tracker
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Campfire Tracker
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A very popular rifle smith built all his non magnum rifles at 21". He had plenty of work.
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Joined: Dec 2005
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Campfire Outfitter
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Campfire Outfitter
Joined: Dec 2005
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we've been cutting muzzleloader barrels down to 20-21" for the last few years. all of them we cut gained velocity. i've had people on here tell that it can't happen but it does.
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Joined: Jun 2012
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Campfire Regular
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Campfire Regular
Joined: Jun 2012
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Is it possible there could have been crown damage or something in the last few inches that could have been slowing a bullet down?
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Joined: Mar 2001
Posts: 12,153
Campfire Outfitter
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Campfire Outfitter
Joined: Mar 2001
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I would guess that the portion of the barrel removed contained a tight spot that slowed the bullet a bit, or it's a result of the shortened barrel being chronographed on a hot day which gave a higher velocity. Established loads are never really "established", they'll all vary from day to day as temperature, humidity and other variables change.
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Joined: Nov 2011
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Campfire 'Bwana
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Campfire 'Bwana
Joined: Nov 2011
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How many shots were sampled during each range session? Once the powder is fully burned, any remaining barrel length is just friction slowing down the bullet.
Every barrel/bullet/powder/cartridge combination has an optimum length.
So, this makes perfect sense. In principle, I agree, but your first statement isn't quite right. After the powder is fully consumed the hot gases continue to expand and accelerate the bullet until pressure drops below the threshold required to accelerate the bullet, which I believe is below 2,000 psi in most cases (I believe MD has mentioned that it takes about 2,000 psi to engrave a bullet, which is more than the pressure necessary to accelerate the bullet once it's beyond the throat). good point. Yep. Everyone else can go browse the .223AI thread now.
You didn't use logic or reason to get into this opinion, I cannot use logic or reason to get you out of it.
You cannot over estimate the unimportance of nearly everything. John Maxwell
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