MBR Calibers
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Thread: MBR Calibers

  1. #1
    Happy Camper hcpookie's Avatar
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    Default MBR Calibers

    I'm not trying to start a "M-16s are the best weapons ever" thread, I'm submitting this for thought. I'm trying to figure this out myself. I know there are no hard-and-fast absolute definitions of an MBR. I accept that the term "Main Battle Rifle" vs. "Assault Rifle" is a relative term.

    OK so we know that a "main battle rifle" is a loosely-defined category where the profile of an MBR is a semi-auto/full auto rifle using a "full stregnth cartridge", with the intended use of engaging man-sized targets out to 500-600 yards.


    So what makes a "full strength cartridge"? Caliber? To me, the specific loadout of a round defines "full strength" - take the AK 7.62x39 "intermediate cartridge" concept (arguably) introduced by the Germans in the "original" Sturmgewehr MP-44 rifle - take a full size cartridge, reduce the load and case size. They started with a full-size 8mm and basically cut the powder in half - presto, the Intermediate Cartridge was born. Therefore my definition of "full stregnth" has always been a cartridge that has the maximum usable powder measure for that bullet.

    Skip ahead to now. One could argue that 5.56x45 is a "full strength cartridge", could they not? Take the .222/.223 round and max it out, you have the .223 remington. SO... given a certain design, a rifle in this caliber could be considered an MBR vs. an assault rifle?

    Or is the fact that it is a cartridge that is "less than .30 caliber" negate its participation in "MBR calibers". Range is certainly not a problem for this caliber. So what qualifies an MBR caliber? Energy delivered at 500 yards? Caliber? Etc.

    We see these "tactical entry models" of MBRs such as a chopped G3/HK91 (aka HK51) or a DSA FAL. Are they still an MBR? One could argue that a "chopped" rifle, even a DSA 16" FAL or paratrooper model, is an Assault Rifle since its long-range functionality has been somewhat neutered. Ditto for its "task orientation" - take off the long-range sights, accept the reduction in long-range muzzle velocity and resultant performance change @ long range, and one could argue these are no longer in the "MBR" classification.

    What other MBR calibers are out there? Seems to me that "MBR" is almost exclusively reserved for .308 caliber rifles. 8mm? .30-06? What models?

  2. #2
    Indian Admin Winn R's Avatar
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    Jerry--I've wondered---How do we classify the 7.62 x 39 cartridge if we up the chamber pressures from 40,000 to 55,000 and increase the velocity to 3000 fps and basically have a 30 caliber projectile traveling at an even faster rate and delivering more downrange energy than it would from a .308?
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  3. #3
    GuncoHolic Templar's Avatar
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    Full power cartidges have traditionally been defined as .30/06, 7.92x57mm, 7.62x54mmR, 7.62x51mm, and even 6.5x55mm........."full power".

    Intermediate power cartridges such as the 7.92x33mm and 7.62x39mm were developed with "intermediate" in mind. Less than the "parent" cartridge, significantly less.

    Then the small bullet high velocity concept came about, and the 5.56x45mm and the 5.45x39mm were put in the same catagory as "intermediate".
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  5. #4
    Gunco Member BattleRifleG3's Avatar
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    "Full Power" seems to have been defined at the turn of the century, by calibers of similar power developed by a number of nations trying to get the most out of smokeless powder. How does one quantify that? You can always make a bigger round. Assume though that you have repeated aimed fire over a number of different ranges from a shouldered arm that must be carried long distances. It must be able to stop man and in some cases machine, and one must carry sufficient ammo to make these aimed shots. Pretty much everyone agreed on what caliber of bullet and what general velocities. Cartridges based on those rounds tome still count as "full power", though their military use may not be as practical as their forerunners.

    It seems to me that these full power rounds were never intended to be fired full auto from small arms. They would be good choices for light machine guns. A small arm may be developed that can fire them controllably on full auto, but that's not the primary purpose, and the cost of doing so (ie extreme noise from a brake and higher weight) may make it impractical.

    Point is that full power rounds were designed for aimed shots when used in standard issue small arms. To me, that means forget full auto and take power over capacity, but keep the recoil reasonable so that shots can be aimed and repeated quickly. It also means decent barrel life, so no overbore magnums or zippers.

    For small arms intended to be select fire, intermediate cartridges are the better choice, which allow for lighter and more compact rifles and designs best suited to that role.

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