The third installment in our discussion of these two very different cartridges, and their use in Mil-surp rifles

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Remington .308 Winchester Managed-Recoil round on left

South African 7.62 NATO Mil-Surp on right

Part I

A Quick Recap

In our recent article, http://www.surplusrifle.com/shooting2006/308vs762nato/index.asp we discussed the real differences between the 7.62 NATO and the .308 Winchester cartridges.   We also discussed the reasons why a rifle chambered for the 7.62 NATO should not be fired with regular .308 Winchester cartridges.                                                                                                                         

In our recent article, http://www.surplusrifle.com/shooting2006/update308vs762nato/index.asp we compared the Federal LR.308 Power Shock load to 7.62 NATO ammunition.  The Federal load, due to developing only 43,000 PSI, was found to be totally safe to fire in any properly functioning Mil-Surp rifle chambered for the 7.62 NATO cartridge (Note.1).  

The arms industry, like many others, is one where different manufacturers often produce products that are similar.  The products, if they are not similar in execution, they are at least similar in function.   This is not a bad thing by any means.  It translates to more choices for the consumer.  Competition for customers leads to lower prices.

Part II

A New Entry

Enter Remington Arms Company, one of the oldest arms and ammunition manufacturers in the United States.

www.remington.com

Remington Arms Company, Inc.
870 Remington Drive
P.O. Box 700
Madison, NC  27025-0700

TEL: 1-800-243-9700
Fax: 1-336-548-7801

Remington .308 Winchester Managed-Recoil ammunition

Remington now has a .308 Winchester cartridge called their “Managed-Recoil” load http://www.remington.com/products/ammunition/centerfire/managed-Recoil.asp.   An alert reader brought the existence of the new Remington ammunition to my attention, and assisted in this investigation.  Thanks James, you are one of the “Good Guys”!    

Remington .308 Winchester Managed-Recoil ammunition contains a 125-grain Core-Lokt PSP bullet and 32.5 grains of a thin, long stick powder

Remington .308 Winchester Managed-Recoil load has a OAL of 2.664

Remington’s unfired case length is 2.007

Remington unfired case, distance from case head to .400 diameter on case shoulder (Stoney Point Gauge)

(Caliper is accurate to +/- .0005)

Remington 125-grain Core-Lokt PSP bullet

(Caliper is accurate to +/- .0005)

The Remington .308 Winchester Managed-Recoil load is advertised as reduced in pressure from the industry standard pressure of 52,000 cup for the .308 Winchester.  The way to reduce pressure in a load is to use less powder of a type (proper burning rate) appropriate for that cartridge, a lighter bullet, or both.   Remington’s new load utilizes a 125-grain Core-Lokt PSP bullet.  This bullet’s jacket is specifically designed to give proper expansion at lower velocity on deer and medium sized game.  The Remington Managed- Recoil load contains 32.5 grains of a long, stick-type powder.  The individual powder sticks are of a rather small diameter.  It appears Remington has elected to use both techniques to produce a load that produces less recoil and less pressure then regular .308 Winchester ammunition. 

Regular production .308 Winchester ammunition, from all manufacturers, is usually right at, or very near industry standard pressure.  Handloaders have always been able to produce “special purpose” ammunition.  The non-handloader had to contend with full pressure loads.  Their only choices were different bullet weights.  Now it appears lower pressure loads are also available to the non-handloading consumer.

Part III

The Control Load

To insure continuity of this test; I utilized the same guns, chronograph and measurement tools as in the previous test of the Federal ammo.  I followed the same testing procedure and same testing sequence as the previous test.  Once again, South African 7.62 NATO ammunition was the standard control load.   Let’s look at the control load.

South African surplus ammo contained 42.6 grains of a short-cut stick powder and a 143-grain FMC BT bullet

South African surplus ammo, length overall

South African surplus unfired case, distance from case head to .400 diameter on case shoulder (Stoney Point Gauge)

(Caliper is accurate to +/- .0005)

South African bullet diameter was .307.5 inch.  Bullet weight was 143 grains

(Caliper is accurate to +/- .0005)

South African unfired case, distance from case head to .400 diameter on case shoulder (Stoney Point Gauge)

(Caliper is accurate to +/- .0005)

South African surplus ammo, unfired case length

Part IV

Range Time & Data Gathering

Spanish FR-8

A model 98-type action rebarreled in the 50’s to 7.62 NATO

The wind coming down thru the canyon is tricky!  A quality spotting scope instantly shows where shots are printing.

I set up the chronograph and placed the Spanish FR-8 Carbine on the bench.  First I fired the 7.62 NATO control loads to condition my shoulder, and to note muzzle blast and take velocity readings.  The pointy 7.62 NATO rounds slipped easily from the magazine of the controlled feed FR-8 into the chamber.  Recoil (shoulder push and muzzle flip) was quite stout.  Even with earmuffs the muzzle blast was loud.  The normal amount of energy was required to unlock and lift the bolt, empties extracted and ejected normally.          

The chronograph gave the following results for the 7.62 NATO load in the FR-8 Carbine (Note2).  Remember, The velocity figures for the South African 7.62NATO ammunition are for comparison purposes only!  Our main concern is pressure.  Our intention is to see if the Remington Managed Recoil load does indeed produce less pressure and recoil then 7.62 NATO ammunition.

South African 7.62 NATO Ammunition / FR-8 Spanish Carbine

Now it was time to put Remington’s Managed-Recoil ammunition to the test.  Remington’s load, utilizing the streamlined 125-grain Core-Lokt PSP bullet fed thru the FR-8 ‘s magazine just as easily as the 7.62 NATO ammunition.  Upon firing, my calibrated shoulder noted a reduction in recoil (shoulder push and muzzle flip) as compared to 7.62 NATO ammunition. Muzzle blast was also reduced.  The recoil difference between surplus ammunition and Remington’s Managed Recoil ammunition was easily noted.  Additionally, I could lift the bolt handle with less energy then was required with surplus ammunition.

Remington’s published velocity figures for this ammunition is 2660 FPS from a 24-inch test barrel.   I expected the velocity in the 18.5 inch barreled carbine to be lower.

The chronograph disclosed the following velocity figures for the Remington load out of the FR-8’s 18.5-inch barrel.  The Remington’s ManagedRecoil ammunition averaged 218 FPS lower velocity.  The difference of 5.5 inch of barrel showed a loss of approximately 39 FPS per inch.   This is just about average.  The Remington’s powder burn curve is right on the money in the FR-8.

Remington Managed-Recoil .308 Winchester Ammunition / FR-8 Spanish Carbine

Indian Rifle 2A-1

An SMLE type, but designed exclusively for the 7.62 NATO

Rounds pass between guide rods on the chronograph for velocity readings

Next I set up the Indian Rifle 2A-1.  The design of the 2A-1’s feeding system caused the NATO rounds to just glide into the chamber. Once again, I conditioned my shoulder to the recoil (shoulder push and muzzle flip), and noted the muzzle blast of the 7.62 NATO ammunition.  Of course with a 25.2 inch barrel and greater weight, the Indian Rifle 2A-1 was much more pleasant to shoot with 7.62 NATO ammunition then from the abbreviated FR-8 Carbine.  The normal amount of energy was required to unlock and lift the bolt, empties extracted and ejected normally.  7.62 NATO ammunition clocked figures that didn’t vary as much as they did in the FR-8.  Notice in the chart below how close the figures are.  Apparently the South African ammunition prefers a longer barrel, like that of the Rifle 2A-1. 

South African 7.62 NATO Ammunition / Indian Rifle 2A-1

I switched to the Remington’s Managed-Recoil ammunition and loaded 5 rounds in the 2A-1’s magazine to start off.  Remington’s Managed Recoil rounds glided into the chamber as easily as surplus ammunition did.  Firing the Remington’s Managed Recoil load in the Rifle 2A-1 showed a greater reduction in recoil (shoulder push and muzzle flip) then it did in the FR-8.  With its greater weight and 25.2 inch barrel, I expected this to happen with the Rifle 2A-1.  Muzzle blast was also greatly reduced. Only a minimal effort was required to lift the bolt handle, and extract and eject empty brass.

Remington Managed Recoil .308 Winchester Ammunition Indian Rifle 2A-1

Part V

Statistical Data Tell A Tale

(Two things that don’t lie; the camera and the Stoney Point Gauge!)

A piece of surplus brass fired in the FR-8, it grew .005 thousands

(The result of normal 7.62 NATO pressure)

A piece of Remington Managed Recoil brass fired in the FR-8, it shrank .0075 thousands

(The result of low (below 7.62 NATO) pressure)

A piece of surplus brass fired in the 2A-1, it grew .010 thousands

(The result of normal 7.62 NATO pressure)

A piece of Remington Managed Recoil brass fired in the 2A-1, it shrank .0025 thousands

(The result of low (below 7.62 NATO) pressure)

Part VI

The Explanation

“What’s that, the Stoney Point gauge shows the surplus brass grew in both guns, BUT Remington’s Managed-Recoil .308 brass shrank in both guns...OK, what gives!!??”  

It’s pretty easy to understand if we just think about it.  Let’s review the firing process.  When the trigger is pressed, the firing pin drives the case forward until forward motion is arrested by either the flanged rim, as in the case of the 303 British, or, in the case of a rimless cartridge such as the 7.62 NATO; when the case shoulder is stopped by the matching area in the rifle’s chamber.  When the case shoulder strikes the matching area in the rifle chamber, the case shoulder is actually pushed back a bit.  So far so good…        

When forward case motion is arrested, the firing pin indents the primer, setting off the round.  Since pressure is applied equally, and in all directions, the bullet must move forward down the barrel.  The primer, being much lighter then the brass case, actually moves backward before the brass case does! The primer backs out of the primer pocket slightly.  The brass cartridge case then moves backwards and reseats the primer as the end of the brass case strikes the bolt face.  

In a cartridge loaded to industry standard pressure, the brass case tightly grips the walls of the chamber.  Now, the only unsupported portion of the brass case is the shoulder.   Pressure will cause the shoulder to move forward until the matching area in the rifle chamber once again arrests it (Note.2).  Such a brass case will be slightly larger then it was before firing (as can be seen by the 7.62 NATO cases fired in both rifles).               

“OK, so how and why did the Remington Managed-Recoil .308 brass cases shrink?”

With Remington’s Managed-Recoil .308 ammunition, when the trigger is pressed, the firing pin drives the case forward until forward motion is arrested when the case shoulder is stopped by striking the matching area in the rifles chamber.    When the case shoulder strikes the matching area in the rifle chamber, the case shoulder is pushed back a bit.

When forward case motion is arrested, the firing pin indents the primer, setting off the round.  Since pressure (lower in the case of Remington’s Managed-Recoil .308) is applied equally, and in all directions, the bullet moves forward.  The primer, being much lighter then the brass case, moves backward before the brass case does. The primer backs out of the primer pocket slightly.  The brass cartridge case then moves backwards.  But, with a low pressure round, things are a bit different.   

Since the pressure is quite a bit lower, the brass cartridge case may not move backwards with enough force to completely reseat the primer.  Not only may the primer stand up in the pocket by 1 or 2 thousands, (Note.4) but also, there will not be enough pressure to cause the brass case to grip the sidewalls of the chamber, and move the case’s shoulder forward.   So, the case is slightly “shrunk”.  That’s exactly what happened with Remington’s Managed-Recoil .308 ammunition in both test Mil-Surp rifles, and proves conclusively, beyond all doubt, that with Remington’s Managed-Recoil .308 ammunition is safe to fire in 7.62 NATO chambered Mil-Surp rifles.  The pressure is lower.                                                       

Remington’s Managed-Recoil .308 Winchester ammunition does indeed achieve the stated goal of reducing recoil and pressure in a caliber .308 Winchester.  This is a boon for the shooter of Mil-Surp rifles chambered in 7.62 NATO.  As shown by the Stoney Point gauge, pressure is lower then the pressure of regular production .308 Winchester ammunition.         

Part VII

Epilog

Remington’s Managed-Recoil .308 Winchester ammunition is a safe, lower pressure, non-corrosive (Note.3) alternative for the man wishing to fire a commercial round in his rifle chambered for the 7.62 NATO round.  This ammunition would make an excellent hunting load for the person wishing to hunt medium size game at close range.  Due to the proven fact that Remington’s Managed-Recoil .308 Winchester develops less pressure then 7.62 NATO ammunition, we can recommend it for use in any properly functioning Mil-Surp rifle chambered for the 7.62 NATO cartridge.

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