Results 1 to 6 of 6

Thread: Bore/Calibre

  1. #1

    Bore/Calibre

    Hi,
    Can someone who really knows give us the details of the above. I understood that if you take a rod of steel, and bore a hole through it, that dimension is the bore. Then if you use a rifling tool and cut grouves in the bore, the dimension from grouve to grouve is the calibre. If this is correct, what words does the "Firearms Act" use to describe the minimum Deer Legal size rifle. I would like to know.
    Marcher.

  2. #2
    Quote Originally Posted by Marcher View Post
    Hi,
    Can someone who really knows give us the details of the above. I understood that if you take a rod of steel, and bore a hole through it, that dimension is the bore. Then if you use a rifling tool and cut grouves in the bore, the dimension from grouve to grouve is the calibre. If this is correct, what words does the "Firearms Act" use to describe the minimum Deer Legal size rifle. I would like to know.
    Marcher.
    It's a complex topic. Firstly the key terms are 'lands' and 'grooves'. The following site has some good info

    - http://www.firearmsid.com/A_bulletIDrifling.htm

    How different cartridges get their names is sometimes not very clear although there are some accepted conventions which have numerous exceptions.

    http://en.wikipedia.org/wiki/Cartridge_(firearms)

    Regards

    JCS

  3. #3
    I was always told that the bore is the calibre and the bore is the bore size and not the groove size. Hence the 30-06 is a .30 calibre despite using .308" bullets. The .458 Win Mag is a .45 calibre the 458" is a marketing name that happens to be the bullet diameter. Winchester did this in the 50's and 60 hence the .308 Winchester. Previously they used the calibre like with the .30 WCF aka 30-30 Winchester. 303 as in the British military round is also bore size and used bullets of 0.311"/0.312"

    The .38 Special is actually a .35 calibre using 0.358" bullets. The original .38 Pistol rounds did use .38" calibre bullets that were heeled to fit into the case mouth. The diameter of the bullets was the same as the cartridge case outside diameter the case was of course rimmed or flanged as the British trade termed it.

  4. #4
    SD Regular
    Join Date
    Dec 2008
    Location
    East Midlands M1/M69 Junction 21
    Posts
    5,388
    ​Of course in olden days when guns were made in ones, twos, or half dozens by local gunsmiths, and people cast their own lead balls, and these guns were mere smoothbore muskets or shotguns you would ask the gunsmith to "bore the steel rod to make a barrel to take twelve lead balls to the pound of lead, or sixteen lead balls (an ounce in fact) to the pound of lead". Thus the origin of a 12 bore or a 16 bore.

    If you take a steel rod and drill a hole through it all you have is a steel rod with a hole through it unless you have stated AS THE TERM OF REFERENCE TO THE PERSON DOING THE DRILLING that you want the bore of the hole such that it will take "twelve lead balls to the pound of lead...etc...".

    Otherwise it just a steel rod with a hole drilled through it of one inch, or half an inch, or three quarters of an inch diameter....or a "bore" as in a hole bored in it of one inch diameter etc. Just as a pipe for domestic plumbing!

    So what I am trying to say is that a hole only becomes a "bore" as in "bore of a gun" if that steel rod is being made to be a barrel, muzzle or breech loading, for a gun. And at that point it is defined by a gunmaker's definition of that diameter bore size as a 12, a 16, a 20 etc., etc., rather than a machinist's definition of it as whole or part inches.

    If you however you wanted a rifled breechloader you would ask the gunmaker to bore the steel rod and chamber it take a cartridge and bullet of such and such calibre. So rifle and chamber it for a A .303 CALIBRE CARTRIDGE. So in fact it is the cartridge that in British convention defines, in law, the calibre of the thing.

    You'd ask a gunsmith, for example, to bore, rifle and chamber a steel rod to take a .38" Special cartridge rather than ask the gunmaker to bore rifle and chamber the steel rod to take a cartridge 1.20 inches long with a case of .376 inches diameter firing a bullet of .358 inches diameter. So the calibre would be .38" Special as until it is chambered all it is, in fact, is a rifled tube with an internal diameter of .358 inches. Which could become a barrel bored and chambered for or IN as the law defines it .38" Special or .357" Magnum, or .358" Winchester or .358" Norma Magnum calibre etc., etc.

    And indeed some gunsmiths may have their own theory that a rifled tube with an internal diameter of .357" would make a better choice than one of .358" internal diameter and select accordingly.

    So until it is chambered a steel rod with a rifled cut hole bored through it is just that. A mere steel rod with a rifled hole of .358 inches diameter. It only, legally in UK, acquires a "calibre" when it is chambered. And the cartridge it is chambered for then in law is what defines its calibre ACCORDING TO THE NOMENCLATURE OF THE CARTRIDGE and regardless of the actual true physical size of the rifled hole in parts of inches.

    So...a British or Australian, Canadian or USA made .303" Lee Enfield will always, in law possess a .303 CALIBRE BARREL regardless of whether that actual rifled hole measures out at .310", .311", .312" or even on some .317"! As it is the cartridge that barrel is chambered for, as mentioned, that defines in law the calibre of the barrel.

    Hope it helps! And also explains why a gunsmith who buys in rifled rod that he then himself chambers and makes into a firearm, rifle, pistol or whatever, will order that rifled steel rod by its internal widest diameter and not by any "calibre".
    Last edited by enfieldspares; 23-11-2013 at 19:34.

  5. #5
    Hi All,
    Thanks for the replies. It IS complicated. So the "bigger than .240 bore/caliber" requirement for a legal deer rifle ( I know there are exceptions, but this is the one I wanted to know about), allows the .243 win, because the cartridge is called .243 . If it was called .236 ( the nominal bore size before rifling) it would not be allowed. But the 7x57 mauser has been called a .275 when the bullet is .284 All very confusing.
    Thanks, Marcher.

  6. #6
    Quote Originally Posted by Marcher View Post
    Hi All,
    Thanks for the replies. It IS complicated. So the "bigger than .240 bore/caliber" requirement for a legal deer rifle ( I know there are exceptions, but this is the one I wanted to know about), allows the .243 win, because the cartridge is called .243 . If it was called .236 ( the nominal bore size before rifling) it would not be allowed. But the 7x57 mauser has been called a .275 when the bullet is .284 All very confusing.
    Thanks, Marcher.
    Actually the 6mm/243 is illegal but shssssssssssssssssssh.. The Police have been pushing folks towards it for years because they didn't know .

Similar Threads

  1. what calibre
    By wirehair in forum Rifles & Calibres
    Replies: 37
    Last Post: 10-04-2013, 12:18
  2. sound moderator bore vs calibre success
    By bewsher500 in forum Equipment & Accessories
    Replies: 16
    Last Post: 01-03-2013, 14:33
  3. Which calibre
    By chr1s in forum Rifles & Calibres
    Replies: 18
    Last Post: 31-01-2013, 19:49
  4. what calibre next ?
    By shaun22/250 in forum Rifles & Calibres
    Replies: 43
    Last Post: 20-02-2012, 19:41
  5. new calibre??????
    By john.d.m in forum Deer Stalking General
    Replies: 10
    Last Post: 26-09-2011, 17:54

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •