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Old 01-31-2010, 12:41 AM
VMFn542bob VMFn542bob is offline
 
Join Date: Oct 2009
Location: Arizona
Posts: 1,066
Default More information on the MANN Accuracy Device

Here is another photo of the MANN Accuracy barrel in early field testing. This photo and the earlier photo in this thread was found linked to this on-line document:
http://www.nps.gov/spar/historycultu...erimenting.htm The following statement there describes the purpose of this device.
"Mann Accuracy Barrel SPAR3728 This barrel is as close to being perfectly accurate as it was possible to achieve. It is used to test the performance of ammunition. Rounds are fired under conditions of controlled temperature, pressure, humidity, and wind. If the ammunition is consistent and the bullet perfect, each round would hit the same point on the target. The Mann barrel was used in testing the T65E5 cartridge, which became the standard NATO round."

This photo clearly shows the two precision "donut" bearings attached to the barrel of the Mann Accuracy Device. It also does not have the "collar" attached to the receiver end of the barrel that appear on later MANN "rifles".
The MANN Accuracy Device is laying on a elaborate test platform with a "V" way with compound adjustments.
The stock has not been cut off, possibly because the design of this platform does not make that necessary.
The MANN "rifle" is not yet positioned in a in a battery position so there is no way of knowing the orientation of the barrel when it was fired.

With the exception to handguns, as far as I know, no receiver has ever been designed to support the weight of a rifle barrel, much less the massive barrel on the Mann Accuracy Device.
Accurizing most rifles require bedding the rifle barrel and receiver. I think that two bearings shown in the field test photos accomplish the same thing.

I also think that if the barrel is supported only at he breech end by that collar, the barrel is floating.
Battleship rifles are supported at only one end and have changes in barrel diameter and tremendous accuracy.


In the case of the currently available barrels, which have a precision collar at the receiver end, the collar can support the weight of the barrel without introducing any stress on the receiver or the gun stock.

TORQUE- When a bullet is fired through a rifled barrel, the rifling must rotate the projectile almost INSTANTLY.
The projectile will pass some of its rotating energy to the barrel causing the barrel to twist (torque).
A wave of energy will be pass down the barrel from the receiver to the muzzle.
I believe those different diameters on my MANN barrels are intended to disrupt that wave before the projectile gets to the muzzle and minimize the effect on accuracy.

Just how much torque is this? The 308 Winchester / 7.62x51 NATO M1A rifle has a muzzle velocity of 2820 feet per second.
The M1A barrel (and the MANN barrel) has a 1 turn in 10 inch twist on the rifling. The length of the M1A rifle barrel is 22 inches.
Doing the math, the unfired bullet sits inside the cartridge, rotating at ZERO revolutions per minute (RPM).
Pull the trigger.
When the bullet exits the muzzle, just 22 inches of travel, it is rotating at about 164,000 RPM.
That kind of torque would rip out your transmission and break you car all over.

Another early Mann barrel testing photo


I don't know how long it may be before I will have the time to test the two MANN barrels I have.
When I do have the time this drawing shows how I plan to support them.
Anyone wishing to use this idea, or any variation of it, has my permission to do so.
I do not think there will ever be any more MANN Accuracy Devices like this made.
I feel sure that advances in technology provide other, easier and more accurate methods for measuring the performance of ammunition and weapons.

A plan to support the MANN Accuracy Device by the collar.
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