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What Defines Rifle Caliber?

Discussion in 'Firearms Certificate (FAC) Guns' started by c4four, Jul 14, 2018.

  1. c4four

    c4four Active Member

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    I was looking over the law regarding semi-autos and I was just wondering, what is it that defines a bullet's caliber. For example: if, somehow, a .223 rimfire cartridge was made, would it be counted as .22 rimfire, as long as it was roughly the same diameter as a .22? This is probably a stupid question to ask, but I don't know much about bullets.
     
  2. rich79

    rich79 No deep or funny comment here

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    I think there's only a couple of thou difference between 22rf & 223, but it's a completely different bullet head, 22rf has a case the same diameter as the bullet, the base of the head has a step to accommodate this.
    If you're talking about an actual 223 bullet head then the case would be wider (like 22 mag) to grip the cannelure so no it wouldn't be the same round.
     
  3. gargloit

    gargloit Posting Addict

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    Just to make life interesting, 223 bullets are mostly .224" diameter. A .22 Hornet round is usually .223".

    22-250, .223, .222, .22 Swift are all .22 centrefires.

    7.55x55, 30-06, 308, 7.62, .30 carbine, all shoot 30 calibre bullets of .308" diameter.

    .303 bullets are usually .311" diameter as are 7.62x39 and 7.62x53.

    .45 Auto bullets are usually .452", 45/70 bullets are .457".
     
  4. pjgtech

    pjgtech Top Poster

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    My Head hurts...... :facepalm:

    :)
     
  5. rich79

    rich79 No deep or funny comment here

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    Here's more confusion, .38 special is the same diameter as .357mag! You can download .303 & use .32 pistol heads out of it, .38-40 is actually .401 diameter!
    The name sometimes has nothing to do with the actual size, it's a can of worms, and that's also without going into the case dimensions as well.
     
  6. 69chris

    69chris Donator

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    could be wrong but i read the po question as.............. if someone took a .223 c/f case and somehow managed to produced those with a r/f style base instead of the usual c/f primer, could we then have a semi auto (ar15 for example) rifle firing .223 r/f rounds

    but i am usually wrong :D
     
    c4four likes this.
  7. Spray1Mark

    Spray1Mark NOW PERMANENTLY BORED!

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    If you are meaning .223 as in .223 Remington cartridge (or 5.56 X 45 NATO) as above this is .224 diameter, the same as amost all .22 rounds, the difference being the construction of the bullet itself.

    In answer to your question the limiting factor is pressure, rimfire cases have a low limiting pressure ability, nothing like that of the remington CF cartridge chamber pressure.

    Power in rimfire cases can only be achieved by bullet weight, there are (or were) larger rimfire cartridges with large caliber heavy bullets, but the speed of the projectile is limited due to the pressure, energy is achieved by using a heavier bullet.

    Whilst in theory the answer is that there is nothing to stop someone making a much larger .22 RF cartridge, the act was really intended to limit the "power" of semi auto rifles.
    Any attempt to circumnavigate this would I suspect end in a prison sentance for the manufacturer (if in the UK).

    However due to the points above it would in practice be a total waste of time as far as effectiveness goes, or else someone would have probably tried it already.

    Just as lever release/Mars etc. are seen by the authorities as trying to get round what they intended to limit civilian ownership to after 1987, they will be out of public hands very shortly I suspect.
     
  8. rich79

    rich79 No deep or funny comment here

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    When .17hmr which is a rimfire was introduced over here people asked if the law could be changed so semi auto's in that calibre could be bought, no such lick there so I doubt any other calibre would get round it.
     
  9. Spray1Mark

    Spray1Mark NOW PERMANENTLY BORED!

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    S/A .17RF was agreed in principle a year or two ago, the reason being less potential for ricochet VS a .22RF. It requires Parlimentary time to change so will take a fair while!
    We argued for the removal of S5 classification of expanding projectiles for 5-10 years before that was finally introduced.
     
  10. rich79

    rich79 No deep or funny comment here

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    Maybe it's be their version of a sweetener when they ban fifty cals & Mars, like Co2 was in 97
     
    c4four likes this.

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