Forums
New posts
Search forums
What's new
Articles
Latest reviews
Author list
Classifieds
Log in
Register
What's new
Search
Search
Search titles and first posts only
Search titles only
By:
New posts
Search forums
Menu
Log in
Register
Install the app
Install
Forums
Rifles, Reloading, Optics, Equipment
Reloading
ladder test help.....
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Reply to thread
Message
<blockquote data-quote="Bart B" data-source="post: 518965" data-attributes="member: 5302"><p>Best way to show how barrels whip and vibrate is shown in the following link:</p><p></p><p><a href="http://www.varmintal.com/amode.htm" target="_blank">Barrel Harmonics Mode Shape Movies</a></p><p></p><p>While the vertical whip of a barrel from recoil causes the most angular change of the muzzle axis, there's still a little bit horizontally. Milli- and micro-scopically, there's movement at the fundamental frequency and its harmonics in all directions happening at multiples of the barrel's resonant frequency. The resonant frequency is low and typically less than 100 Hz or cycles per second. Bullets from centerfire rifles are long gone before the barrel goes through one cycle. </p><p></p><p>Variables that change how much the barrel whips and vibrates at this low one and the higher frequencies are caused by out of square case and bolt face, non-repeatable bolt lockup positioning, the angle of the recoil axis to the object mass (machine rest, free recoil on bags, held by a human) that holds the rifle. Most of the horizontal group variables are caused by this. Then there's the bullet; if unbalanced in any way, the centrifugal forces caused by its spin will move the bullet's flight axis away from the bore axis by some degree.</p><p></p><p>Other causes of greater vertical shot stringing are a weak firing pin spring not detonating the priming compound uniformly. Powder charge position in the case. How hard one holds the rifle against their shoulder; a 100 fps spread across two folks shooting the same rifle-ammo combo and one person producing smaller standard deviation in velocity has been proved many times over. Check some ballistic tables and note the difference in bullet drop down range for a 20, 40 and 60 fps spread in muzzle velocity; it's a couple tenths of an inch at 100 yards, a couple dozen inches at 1000.</p><p></p><p>At my request, software was written by Tom Irvine at the following link to calculate the natural or resonant frequency of rifle barrels. It provided answers for a 2 and 3 taper barrel by entering the diameters at different points, their spacing and the bore diameter. It's available at:</p><p></p><p><a href="http://www.vibrationdata.com/updates.htm" target="_blank">http://www.vibrationdata.com/updates.htm</a> at about 2/3rds down this page.</p><p></p><p>Note that when you screw the chambered barrel in a receiver, fit the barreled action to the stock then mount a scope on it, the fundamental of the barreled action will change a small amount. But it does show the differences between different caliber and barrel contours for different lengths. An interesting thing to check out.</p></blockquote><p></p>
[QUOTE="Bart B, post: 518965, member: 5302"] Best way to show how barrels whip and vibrate is shown in the following link: [url=http://www.varmintal.com/amode.htm]Barrel Harmonics Mode Shape Movies[/url] While the vertical whip of a barrel from recoil causes the most angular change of the muzzle axis, there's still a little bit horizontally. Milli- and micro-scopically, there's movement at the fundamental frequency and its harmonics in all directions happening at multiples of the barrel's resonant frequency. The resonant frequency is low and typically less than 100 Hz or cycles per second. Bullets from centerfire rifles are long gone before the barrel goes through one cycle. Variables that change how much the barrel whips and vibrates at this low one and the higher frequencies are caused by out of square case and bolt face, non-repeatable bolt lockup positioning, the angle of the recoil axis to the object mass (machine rest, free recoil on bags, held by a human) that holds the rifle. Most of the horizontal group variables are caused by this. Then there's the bullet; if unbalanced in any way, the centrifugal forces caused by its spin will move the bullet's flight axis away from the bore axis by some degree. Other causes of greater vertical shot stringing are a weak firing pin spring not detonating the priming compound uniformly. Powder charge position in the case. How hard one holds the rifle against their shoulder; a 100 fps spread across two folks shooting the same rifle-ammo combo and one person producing smaller standard deviation in velocity has been proved many times over. Check some ballistic tables and note the difference in bullet drop down range for a 20, 40 and 60 fps spread in muzzle velocity; it's a couple tenths of an inch at 100 yards, a couple dozen inches at 1000. At my request, software was written by Tom Irvine at the following link to calculate the natural or resonant frequency of rifle barrels. It provided answers for a 2 and 3 taper barrel by entering the diameters at different points, their spacing and the bore diameter. It's available at: [url]http://www.vibrationdata.com/updates.htm[/url] at about 2/3rds down this page. Note that when you screw the chambered barrel in a receiver, fit the barreled action to the stock then mount a scope on it, the fundamental of the barreled action will change a small amount. But it does show the differences between different caliber and barrel contours for different lengths. An interesting thing to check out. [/QUOTE]
Insert quotes…
Verification
Post reply
Forums
Rifles, Reloading, Optics, Equipment
Reloading
ladder test help.....
Top