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extraction without taper?

Discussion in 'Rifle Country' started by labnoti, Apr 27, 2019.

  1. labnoti

    labnoti Member

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    It seems more and more "modern" cartridges are forsaking taper to increase capacity in a short action without increasing bolt face diameter and thrust. The 7.62x39 is an example of a very tapered cartridge so designed to extract reliably with steel cases, but even while cases were readily available in brass, many like the .30-03, -06, .270, .45-70, 9.3x62, .375 H&H, 30-30, 5.56x45, and .308, were designed with taper that's being omitted in "modern" designs like Creedmoor, Grendel, PPC, Bushmaster, Nosler, MARS, Valkyrie, and on and on.

    So what's the trade-off? Why did most of metallic cartridge history from the 19th through 20th centuries favor tapered cases and now we don't seem to need them anymore?

    Are these untapered cartridges going to fail to extract in extreme cold, heat, or with contamination from dirt, mud, snow, ice? Are they dependable or just geared toward sales to internet-researching ballistic table shoppers?
     
  2. lysanderxiii

    lysanderxiii Member

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    Not if the case is made correctly.

    mnFRckt.png

    Even with highly tapered cases such as 7.62 x 39 the taper is still straighter than a Morse taper which is a self-locking taper, which means if there is any interference, the case will lock in place.
     
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  3. Varminterror

    Varminterror Member

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    Lot of these rounds were designed to feed in automatic weapons. Most of these modern cartridges were not.
     
  4. Goosey

    Goosey Member

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    I don't think it matters to most people. Most of the cartridges you mentioned weren't designed for military service. Most of them feed and extract fine for civilian use. I don't think the likes of the 280 AI would prove all that great in automatic weapons... if pressed into such service I think it would be renamed "280 Ackley Impaired". I don't think straighter walls and sharper protruding shoulders necessarily make "better" designs... that depends on the purpose.

    Some case wall tapers for comparison:

    6.5 Creedmoor: 0.17° (30 deg shoulder)
    280 AI: 0.25° (40 deg shoulder)
    6.5 Grendel: 0.32° (30 deg shoulder)
    300 WSM: 0.33° (30 deg shoulder)
    308 Winchester: 0.34° (20 deg shoulder)
    30-06: 0.47° (17.5 deg shoulder)
    223 Rem: 0.50° (23 deg shoulder)
    6.8 SPC: 0.50° (23 deg shoulder)
    338 Lapua: 0.60° (20 deg shoulder)
    416 Rigby: 0.63° (45 deg shoulder)
    8x57 IS: 0.66° (19.1 deg shoulder)
    5.45x39: 0.80° (20.3 deg shoulder)
    6.5x55 SE: 0.83° (25.6 deg shoulder)
    5.8x42 Chinese: 0.94° (24.5 deg shoulder)
    300 H&H Mag: 0.96° (8.5 deg shoulder)
    7.62x39: 1.34° (16.4 deg shoulder)
     
  5. Varminterror

    Varminterror Member

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    I know I ran my bolt as fast as I could physically do so at a match today, and experienced ZERO feeding failures with my “low taper” 6mm Creedmoor...
     
  6. Macchina

    Macchina Member

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    Also remember that a lot of those cases were designed in an era when extreme tolerances and high strength steel weren't what they are today. All cases have clearance to the chamber they fit in and a properly designed action will not expand enough to allow the case to exams expand with it and lock in place when it doesn't bounce back.

    I'm a engineer and we have a saying that goes something like "a lot of people can make a part that will never fail with unlimited material, it takes an engineer to design a part with the correct amount of material."

    What this means is that the firearms engineers would not be doing their jobs if they weren't finding the little ways to constantly increase case volume while decreasing action weight. They didn't just REMOVE the taper, it was DESIGNED out.
     
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  7. Steel Horse Rider

    Steel Horse Rider Member

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    I have never had a problem with extraction in my Marlin .357 mag lever gun in cold, hot, wet, or dry conditions. So what is the question?
     
  8. rbernie
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    rbernie Member

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    So let’s ask the question slightly differently but still with the intent of the OP – why is it that early gun designers seemed to believe that case taper increased the reliability of loading and extraction?
     
  9. Riomouse911

    Riomouse911 Member

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    I know the early English safari rounds were designed to feed and extract in very high heat with high humidity, something not encountered in England. I’ll guess without the benefits of computer modeling the designers found a highly tapered case gave them the 100 pct reliability dangerous game requires. This is found both in the Nitro Express double rifle rounds and in bolt action rounds from Holland&Holland, Jefferey etc.

    The .416 Rigby isn’t anywhere near as tapered as the .375 H&H or .404 Jefferey, I’ll guess that design team figured out it didn’t need such an extreme taper to work well.

    Stay safe.
     
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  10. Goosey

    Goosey Member

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    "The case is the copper tube which forms the receptacle for the powder charge, the percussion compound, and the leaden bullet. Its exterior conformation is designed to facilitate its ready extraction from the chamber of the gun after firing. Besides the rim at the closed end, which is intended, primarily, to assist extraction, the case is tapered from the rear to a point where it seizes the bullet, whence it merges into a right cylinder."
    —Report of the Board on behalf of the United States Executive Departments at the International Exhibition held at Philadelphia, PA., 1876

    "The cartridge selected had been designed by Mr. Pedersen with features making it especially suitable for automatic firearms, such as an increased taper for easy extraction."
    Hatcher's Notebook

    "The design of the cartridge (Soviet M1943 7.62x39mm) has provided the cartridge case with a very pronounced taper. Tapered cases exert more pressure on the bolt and less on the walls of the chamber (in the barrel) than less tapered cartridges. This feature makes tapered cartridges easier to extract than other cartridges and is an especially desirable feature when rifle chambers are dirty and scored, or when the cartridges are improperly made, corroded, or vary in loadings."
    Infantry, Volume 65, No 3

    "To ensure ease of extraction, it is desirable that the main body taper should not be less than 0.02 inch per inch on diameter."
    —AMCP 706-247, Engineering Design Handbook, Ammunition Series, Section 4, Design for Projection

    "In guns using cartridge cases the taper of the chamber is made the same as that of the cartridge case. In some chambers, the part that accommodates the straight portion of the case is given a taper of 0.005 in. per in. on diameter. This taper has been found to facilitate the extraction of drawn steel cases."
    —AMCP 706-247, Engineering Design Handbook, Ammunition Series, Section 4, Design for Projection


    The last two are in reference to artillery. But same concepts.

    But if someone finds a round can have greater capacity or less case stretch after giving sharper shoulders and less taper, while still feeding and extracting to his satisfaction, as the rounds you mentioned almost always do, he will probably see the advantages in such.

    Not only the early designers. Look at the Soviets' 5.45x39 (introduced 1974) or the Chinese 5.8x42 (introduced 1987). If they could design ICBMs, I'm sure they had folks who knew what they were doing when designing their new service rounds. It should however be noted that their cases are both steel.
     
  11. Alaskan Ironworker

    Alaskan Ironworker Member

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    Clamp a marlin spike in a vise, then clamp a piece of roundstock in a vise. Which one takes less force to remove? Also, assuming your vise jaws havent moved, which one is easier to Re-insert? Simple way to think of the fundamentals.
     
  12. Dave DeLaurant

    Dave DeLaurant Member

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    One element involves early theories of optimum accuracy via bore concentricity with self-contained brass cartridges. Right at the beginning of Mann's "The Bullet's Flight" page 4, in a discussion of the Stevens 32-40 taper-chamber rifle: "It was thought that the bullet resting in the throat of the rifle. . .on a true taper with the lands left by the tapering reamer in the chamber must be in a position before discharge to lay straight and central with the bore." Mann states this case was combined with a tapered bullet going from .318 to .320".

    The desire to ease extraction during the early black powder cartridge days can be seen in the reverse taper on the Burnside cartridge's "ice cream cone" case, a feature adopted solely to ease mechanical extraction. Not all designers bought into the concept -- consider the early Maynard cases with straight walls, a big honking rim and no mechanical extractor.
     
    Last edited: Apr 28, 2019
  13. someguy2800

    someguy2800 Member

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    I think lack of case taper is pretty much a non issue with a modern firearm with clean burning powders, non corrosive primers, and where the firearm and ammunition are kept clean, as is the case with non military use. When everything is clean and loads are within the pressure limits of the chamber, a straight wall case doesn't extract any harder than a tapered case. Even AR's work just fine with straight wall cases.
     
  14. Alaskan Ironworker

    Alaskan Ironworker Member

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    high pressure straight walled cases can stick fairly easily with slight “hotrod reloading”. .454, 460, 500 s&w etc.
     
  15. rbernie
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    rbernie Member

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    This example assumes / requires that both the male and the female tapers are of equal / close dimension, and have no elasticity. In the case of a breech loading chamber, there is inherent design clearance between the case and the chamber wall, and the case material (as you pointed out) is chosen for elasticity.

    My personal theory has always been that case taper was a way of dealing with the early 20th century reality of machining marks in the chamber - the taper assured that the brass would not get locked into the chamber due to interference between the inevitable chamber rings and the impression of those rings on the brass. The greater the case taper, the more pronounced the chamber machining rings could be without causing failures to extract.

    As machine processes have gotten more precise and repeatable over the last 100 years, the dependency on taper has been reduced.
     
    Last edited: Apr 28, 2019
  16. Walkalong

    Walkalong Moderator

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    That may very well be true, especially with mass made military weapons where speed was more important than quality.

    No doubt in my mind more taper would extract more easily and help with a rough and/or dirty chambers in tough environments.
     
  17. lysanderxiii

    lysanderxiii Member

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    Once a case is subjected to the chamber pressure of firing, it is the same taper as the chamber. (wink)

    My point was that elasticity is required even with the old highly tapered cases, and if the case shrinks away from the chamber wall you can reliably extract, even with cylinder cases, such as .38 Special.

    And you forget that 100 years ago isn't as long ago as you think. In 1919 they were making some finely machined bores and chambers, look at M1903s and the like. Even in 1895 the art of reaming chambers smoothly was well understood. But, I think you are on the right track, though I believe it was more due, first, to black powder fouling, and later, the inevitably dirty, and after some service with corrosive primers, pitted chambers that drove the pronounced taper of early cartridges.
     
  18. rbernie
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    rbernie Member

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    I’ve looked at a lot of chambers through a lot of borescopes. As good as they might have been in period, my Lowe or Gustaf chambers don't look nearly as devoid of deep machining marks as most anything else that’s been made since World War II. Of course the war years production versions for military rifles and most cheap civilian rifles have shown the worst chamber finishes, due to the speed with which the chambering process was conducted.

    I think the items in concurrence are that the proper case material will facilitate extraction through proper elasticity regardless of chamber / brass shape, and that case taper will facilitate extraction when the chamber wall has the ability to imprint high/low patterns onto the brass that could provide mechanical interference.
     
  19. Varminterror

    Varminterror Member

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    Because MANY of the parent cases designed throughout history have been developed with automatic fire in mind.
     
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