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Problems with rimmed cartridges in automatic weapons

Discussion in 'Small Arms and Edged Weapons' started by superbee, Jan 9, 2012.

  1. superbee

    superbee Member

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    I have read that one of the reasons the United States moved away from the 30-40 Krag round to the 30-03 (later 30-06) Springfield round for its small arms was that it was difficult to get a rimmed cartridge to feed reliably through many automatic weapons.

    Yet Great Britain and the Soviet Union fought both world wars with a rimmed cartridge. Did their armies experience such difficulties?
     
  2. brndirt1

    brndirt1 Saddle Tramp

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    I won’t claim this is "the" reason the US moved away from the rimmed cartridge, but perhaps the main one. From the turn of the 20th Century there was one dominant inventor driving American automatic weapons; John Browning. His actions were very reliable, and they used semi-rimless cartridges.

    Remember his original "potato digger" machine gun was designed to fire rimmed cartridges, i.e. the 6mm Navy and Krag, but could be modified to fire rimless later. He and Fred Moore at Colt worked to improve the design of his first .38 semi-auto pistol, which fired a rimmed cartridge, and in so doing developed a "rimless" (actually semi-rimmed) cartridge during the Spanish-American war period. And by 1900 it was on sale. From that time on his actions seemed to favor the semi-rimmed style of cartridge, and America adopted his actions, and consequently other weapons were designed to use the cartridge.

    America preferred the very reliable Browning actions, and that sort of dictated the cartridge type. Just a thought.
     
  3. harolds

    harolds Member

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    Yes Clint, we relied heavily on the work of John Moses Browning with one exception: our 1903 and 03A3 rifles. These were actually slightly modified Mauser actions. Mauser used rimless cartridges and these were more dependable than rimmed ones when working through rifle and MG actions. In fact, the 30-03/30-06 cartridges are based on the 7.92X57 case. There is another thing about the rimmed cartridges: If you look at the 303 L-E, the 7.62X54R, 8mm Lebel and 30/40 Krag cartridges, they are very fat at the base and taper forward. That means for box magazine rifles such as for the BREN, where you have 20-30 round capacities, you end up with very curved magazines. Such magazines are harder to make dependable. It can be and was, done but straighter cases cause fewer headaches in semi and full auto weapons. Also, the rim itself can cause feeding problems if one isn't careful.
     
  4. Takao

    Takao Ace

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    It is usually referred to as "rim lock", the magazine has been improperly loaded.

    Hickok45 experiencing "rim lock" with a Lee Enfield during the first 4 miuntes of the video. He explains what happened in the pop-up blurbs at the top of the video. Enfield ( Chapter 2 ) - YouTube

    "Rim lock" explained and how to properly load a Mosin-Nagant stripper clip
    How to properly use the Mosin Nagant stripper clip - YouTube

    Showing of the "rim lock" prevention device on the Mosin-Nagant, and trying to "rim lock" the Mosin. In the video, the device functions as intended, but this is not always the case.
    Mosin Rimlock Attempt - YouTube
     
  5. brndirt1

    brndirt1 Saddle Tramp

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    As I was only addressing American autoload weapons I only reported on J.M. Brownings impact on our choice of the "rimless". You are completely correct, but I was really only thinking about why we (America) focused on rimless for our autos.
     
  6. superbee

    superbee Member

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    "Such magazines are harder to make dependable. It can be and was, done but straighter cases cause fewer headaches in semi and full auto weapons."

    I guess the fact that all major military powers have long since gone to a rimless case is pretty strong supporting evidence. Thank you all for the responses.
     
  7. mac_bolan00

    mac_bolan00 Member

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    correct me if i'm wrong but the only automatic feeding problem one can have with rimmed cartridges is when the cartridges are stacked and feeding is done along the axis of each cartridge. for arrangements wherein feeding is perpendicular to the cartidges (like with belts or drum magazines) there is no problem.
     
  8. MikeRex

    MikeRex Member

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    Nope, belts and drums are still a problem. The rounds do translate sideways in a belt or a magazine, but they still need to be stripped forwards (or in the case of a lot of Russian MGs, backwards and then forwards) to feed into the chamber. The only exception are extremely rare "nutcracker" rotary breech weapons or open-chamber "tround" designs: SPLIT BREECH GUNS: THE NUTCRACKER AND THE 40MM MK 18
     

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