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-   -   Mann Accuracy Device (http://forums.thecmp.org/showthread.php?t=6338)

wvminer 01-18-2010 04:27 PM

Mann Accuracy Device
 
Any ideas on mounting a Mann device? I am thinking about buying one and want to be able to use it.

joe wilson 01-20-2010 02:48 PM

A CMP member did a good job on mounting one. He has it for sale in the WTS bolt action section I believe.

VMFn542bob 01-20-2010 04:41 PM

Quote:

Originally Posted by joe wilson (Post 49426)
A CMP member did a good job on mounting one. He has it for sale in the WTS bolt action section I believe.

It has been sold but the buyer and seller and several others who have a MANN Device can be found on this active thread.
http://www.thecmp.org/forums/showthr...highlight=MANN

wvminer 01-21-2010 02:39 PM

I must have had a senior moment. I didn`t look at the whole thread on the Mann build job. I just glanced at the last part when I first saw the info. That is a beautiful rifle and a great job.

rocknrod 01-22-2010 08:28 AM

I read the whole post.
I had to look up what a Mann accuracy device is :)
http://www.odcmp.org/1001/mann_inc.asp

UncleWilly 01-25-2010 02:44 AM

I read the above referenced link and while I found it interesting, it STILL failed to explain just what the heck the Mann devices are and how they were used, other than the obvious, that they are fat barrels screwed into bolt action receivers. Anyone? Anyone? Bueller? Bueller? They are obviously used for some kind of testing, but how about some examples or description please. Thanks. :-)

VMFn542bob 01-25-2010 10:43 AM

Quote:

Originally Posted by UncleWilly (Post 52335)
I read the above referenced link and while I found it interesting, it STILL failed to explain just what the heck the Mann devices are and how they were used, other than the obvious, that they are fat barrels screwed into bolt action receivers. Anyone? Anyone? Bueller? Bueller? They are obviously used for some kind of testing, but how about some examples or description please. Thanks. :-)

Information on the MANN barrel is very scarce but I think a picture is worth a thousand words. Last year I placed a post on the old forum regarding this subject but the link to that post is not currently active.
Here is the text of that post which includes links to a photograph of the MANN device as it was used early on and my observations and conclusions. Take it for what it's worth. I think the MANN barrels currently available from the CMP are a great value but if you want to alter it to look like a sporting rifle it will cost you.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
posted 9 July 2009
VMFn542Bob
Posted - 07/09/2009 : 11:20:38
--------------------------------------------------------------------------------
In my humble opinion -
The mann accuracy barrels were designed to test ammunition only.
The barrel was designed to eliminate all possible influence it might have on the performance of the ammunition.
The 1903-A3 receiver was chosen because of its availability and known reliability.
Early testing was done in the field where the barrel was fitted with two precision steel bearings, or donuts.
One bearing was placed near the breech and the other near the muzzle.
Photos I have seen indicate they were secured to the barrel with a set screw.
The device was then placed up-side-down on a precision steel "V" way block securely attached to a stable platform.
The precision of the bearings and the "V" way allowed the device to be returned to the same firing position after each shot with minimal affect on the direction of aim.
Sights were not needed because the device was testing the repeatability of ammunition, not the devices ability to hit a bull eye.

The devices currently available at the CMP are fitted with a collar near the breech.
It is my professional opinion that this was used to secure the device to a stationary platform, perhaps indoors, allowing the barrel to otherwise float freely.
This would have been an obvious improvement over the method used for testing in the earlier days shown in the photos where the barrel was supported at both ends.
I have already placed an order.
I plan to make a platform to hold the device by the collar in my Hyskore Dangerous Game Machine Rest with provisions for a Picatinny rail above the collar to mount a scope. I will make no modifications that will not allow it to be restored to it's original configuration.
If I live long enough.

Early field testing photo
http://www.nps.gov/spar/historycultu...l_shooting.jpg
Mr. Al Woodsworth, Springfield Armory, testing ammunition from a Mann accuracy barrel supported in an improvised rest made from a machine gun mount. (Caption found in Lt. Col. William Brophy's book "The Springfield 1903 Rifles"
(This comment was added here 2/28/2014)

Closeup of the same photo
http://i623.photobucket.com/albums/t...ing8x10JPE.jpg

The CMP Mann Accuracy Devices by Steven T. Rutledge
http://www.odcmp.org/1001/mann_inc.asp

--------------------------------------------------------------------------------
Edited by - VMFn542Bob on 07/09/2009 11:22:40 ; 02/29/2014

VMFn542bob 01-25-2010 02:40 PM

My MANN Accuracy Device Barrels
 
MANN Accuracy Device barrels & 1903-A3 Springfield
This photo (TOP) shows two Mann Accuracy Device barrels chambered for the 7.62mm NATO (.308) which I received from CMP Sales in 2009.
They have 21.5" stainless steel barrels with a 1 turn in 12 inch right hand twist rate fitted to Remington 1903-A3 receivers.
The barrels and the receivers appear to be new and are in pristine condition. If they have been fired it was only a few times.
They are pictured above a 1903-A3 (30-06) Springfield that I bought for $45 through an advertisement published in the American Rifleman Magazine in early 1970s.
The rifle was assembled with surplus parts, a new GI barrel and a new aftermarket receiver.
I removed the front sight and replaced it with an IDEAL (later Lyman) Olympic sight.
I saved the original sight. I also refinished the stock. It is a real good shooter.
http://i623.photobucket.com/albums/t...1903-A3Spr.jpg

Remington 1903-A3 Receivers on MANN devices
Top view of receivers and closeup of rear sight dovetail - rear sight not included
A commercial scope mount is available that attaches to the rear sight dovetail but it requires modification to the stock and bolt.
http://i623.photobucket.com/albums/t...onMANNdevi.jpg

Outside Dimensions of MANN barrels
View of MANN barrels showing different steps in diameter
Collar overall length (including shoulder) = 2.760 inches
Coller shoulder width - 0.503 inches
Collar minor diameter = 1.5000 inches (very finely finished)
Coller major diameter (shoulder) = 1.757 inches
Barrel diameter (4 sections, from collar to muzzle)
Section 1 = 1.250 inches : Section 2 = 1.232 inches : Section 3 = 1.244 inches : Section 4 = 1.236 inches
These diameters vary approximately +/- 0.003 inches across each section and from one barrel to the other.
The location of the steps on each barrel are within a few thousands of an inch in same place on both barrels.
http://i623.photobucket.com/albums/t...ANNbarrels.jpg

My professional opinion of the purpose for the steps in barrel diameter is a well thought engineering plan to purposely break up the normal resonance of the barrel and elimiate as much inaccuracy as possible created by the barrel. I believe that to remove it for cosmetic purposes would be a mistake.

UncleWilly 01-25-2010 07:08 PM

So I gather from this that SOMEONE in the Army would lock this barrel into a fixed frame and use it to test ammunition? You could measure projectile velocity and group size without having to account for any (or much) barrel vibration. Obviously this wasn't issued at the tactical level but only to higher level arms labs. Any idea who used them? Perhaps those organizations have some kind of unit history that would show them in use.

VMFn542bob 01-25-2010 07:28 PM

Quote:

Originally Posted by UncleWilly (Post 52667)
So I gather from this that SOMEONE in the Army would lock this barrel into a fixed frame and use it to test ammunition? You could measure projectile velocity and group size without having to account for any (or much) barrel vibration. Obviously this wasn't issued at the tactical level but only to higher level arms labs. Any idea who used them? Perhaps those organizations have some kind of unit history that would show them in use.

You and I are of the same mind with your first statement. I haven't a clue how they would have measured velocity back then, when those old MANN barrels in the photo were tested. But the addition of the precision collar that is present at the breech on the current rifles leads me to believe that is where that version MANN rifle was supported, probably on a sled, and that the barrel was as free floating as it could possibly be without floating in space. As previously stated, I can only conjecture about this unique 'rifle'. I feel certain that the Army specified how it was to be made and in all likelyhood the manufacturers of ammunition contracted to the military were required to use it for testing. I have no idea what may be used now because technology runs faster than my mind. No doubt there is plenty of information available on this device under the current 'Freedom of Information' laws for anyone having the financial resources to look for it.

edlmann 01-26-2010 09:13 AM

Quote:

Originally Posted by VMFn542bob (Post 52672)
I haven't a clue how they would have measured velocity back then, when those old MANN barrels in the photo were tested.

Back before the development of the modern chronograph, I believe velocity was tested by firing a projectile at a swinging pendulum of a known weight at a known distance. High speed photography would measure how far the pendulum was moved and the velocity computed from that.

Prior to Oehler's chronograph, a lot of inaccurate velocity estimates were in print.

UncleWilly 01-26-2010 06:34 PM

I've seen pictures of those old pendulums. They predate high speed photography. The pendulum moved a very light weight indicator needle around a dial and when the pendulum fell back, the needle stayed at its maximum moved location. Pretty clever device. If everything was weighed and measured accurately, some standard physics equations would yield the velocity.

americal71 01-27-2010 12:37 AM

Perhaps I can shed a very little light on the subject. Every lot of military ammunition had to meet accuracy requirements to be accepted. For example, M118 7.62 Match ammunition had to produce a 3.5 " mean radius at 600 yards. Samples from each lot were sent to a testing facility - at various times this could have been Frankford Arsenal, RIA, APG, etc. At some point the manufacturing facilitiies were required to have their own test set up. I believe as late as the '50's and '60's the Govt had personnel stationed on sight (military or civilian) to observe and certify the results. As you see in those old photos at an early time they actually tested at the required range. Later they built tunnels to limit the effect of wind and climate and fired the ammunition using the Mann devices as a known constant test bed at 100yds/m and extrapolated the results. The number of test required resulted in a large number of the devices and the barrels being manufactured. I know that SA, FA, and later RIA manufactured most of the barrels.
When I was at RIA in the '70's Rodman Lab still had Mann devices that could be mounted into a machine rest with a large armor shield that were used in ammunition development. The only test I witnessed using these devices was in development of the projectile profile for the 6mm SAW cartridge. Shortly after that, the lab was closed down and the equipment and mission transferred to Picatinny Arsenal. Hope this may help!

VMFn542bob 01-29-2010 09:23 AM

Quote:

Originally Posted by americal71 (Post 53438)
... Hope this may help!

Sure helps me and confims what I suspected. It makes a lot of sense to shoot through a tunnel. Not only can wind effect be eliminated the entire environment can be controlled inside a tunnel: altitude, humidity, temperature etc, about every variable that can affect the performance of the bullet. With the design of the MANN barrel reducing its effect on the bullet to the maximum extent possible, and the tunnel controlling the environment, the only variable left is the ammunition. That would seem to imply that group width would be then be related to the projectile and group height would be related to the velocity. Because many things can affect velocity that is probably where ammo manufacturers concentrate their attention.
A little trivia: I have read that the performance of the black powder 45-70 GOVT cartridge was so bad that the shape of the bullseye was changed to accept the fact that velocity could not be controlled well enough to shoot at a round bullseye. As a result, the military competition target was changed from a round bullseye to a bullseye that was about twice as high as it was wide.

VMFn542bob 01-31-2010 12:41 AM

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
http://i623.photobucket.com/albums/t...eltesting2.jpg

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.
http://i623.photobucket.com/albums/t...lsupported.jpg

mousegun 03-18-2010 07:05 PM

Quote:

Originally Posted by edlmann (Post 52940)
Back before the development of the modern chronograph, I believe velocity was tested by firing a projectile at a swinging pendulum of a known weight at a known distance. High speed photography would measure how far the pendulum was moved and the velocity computed from that.

Prior to Oehler's chronograph, a lot of inaccurate velocity estimates were in print.

The ballistic pendulum went out of serious use at armories over a hundred years ago. Instrumental velocities in the time of John Garand were quite accurate and reliable if not tedious to measure. According to Hatcher's Notebook on page 251 service ammunition was measured with a Le Boulongé chronograph. The setup and method of measuring instrumental velocities with the chronograph is described on page 404.

A typical chronometric measurement around the turn of the century was probably made with an electromechanical apparatus consisting of frangible detector screens, a source of high voltage and a recording device. The recording device was usually a hysteresis/synchronous motor driving a waxed disk with a conductive backing on a spindle. A worm grear drove a stylus in a spiral track on the disk. High voltage (90-200V) was connected across the fragible screens and the leads connected to the stylus through a "kicking" inductor. As the bullet passed through the screens the short caused a high voltage spike on the stylus to arc through the disk. The angular distance on the disk between two arc spots indicated time of flight. Very accurate...

..and expensive.


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