meaning of calibre

[eljefe]

Khan_imran, now you know why you were welcomed to the madness?
Ok, caliber =diameter of the barrel- most times
So if you hear of a .303 lee enfield-it means a rifle chambered for the proprietary 303 cartridge.
The confusion arose aprtly when wildcatters(term used for experimental gunsmiths and shooters) decide to retain the bullet/barrel diameter but boosted up the case dimensions to increase the powder charge and the range etc.
One example of this is the 44 special and 44 magnum
similarly, the 38spl and the 357 magnum which has a case longer than the 38 special. So a 38 spl can be fired in a 357 mag, but NOT vice versa.Ditto 44 spl and 44 mag
The European manufactures also muddied up the water a fair bit by designing and naming their cartridges in metric , but with different case shape/ contours so a 8mm ABC wont fit in a 8mm XYZ and the PR types went hoarse shouting at the marginal gain in velocity and muzzle energy of 'their' 8mm Vs the oppositions 8mm.A whole lot of marketing hype...End result, trying to find an exact caliber of an 'Obsolete ' caliber / rifle in India/ subcontinent needs long extinct gunsmith skills to do a chamber casting etc.
One more bit to the jigsaw
the measurements we hear often- again I quote the example of the 303 Enfield/British- .303 is the dia of the muzzle-NOT the bullet.The bullet is actually BIGGER and the dia is 0.311 inch.If the barrel and bullet dia had been the same, the bullet would slide out..When its marginally tighter( as determined by gigabytes of testing by ballisticains!) the bullet forms a sort of a gas seal
( obturation) by the burning propellant gases when is fired, and 'engages in the grooves', starts spinning -either CW or CCW -which ever way the grooves are cut, and it is all this which contribute to range/ velocity/muzzle energy
Now that you are partly confused, google around a bit and come back in time for the 3rd instalment...
best
Axx

[Khan_Imran]

Very well elaborated Sir. The text is certainly worth a go through.

IMRAN.

[Grumpy]

I always suspected el Jefe was a politician.......Taking what has previously been said and re-presenting it as original..........
Tony Blair is probably in need of a `spin doctor` should you be considering a change of career Asif.
( )
( I happen to think that is one of my best yet........pity it`s so subtle and hardly anyone will `get` it ! )

" .303 is the dia of the muzzle"

Er........Oh no it isn`t. Of the whole bore you mean.

[TenX]

A whole lot of info here. However, can someone tell me if the 'Rifling' (or the 'grooves' which make the trajectory spin) is cut or is projected?

[Mack The Knife]

Err...Anand, you cannot make the 'trajectory' spin.

Rifling can be done by cutting, pressing or forging.

[eljefe]

Grumpy, my typing -2 finger , left handed on a good day-is unfortunately slower than the thought processes, which merely crawl along at 'kerbspeed' - did mean bore, i think
Have plenty of chance to start spindoctoring right here, so Toney tony will have to wait a while
Imran-the hole in the barrel aka the bore
The dia of the entire barrel at the MUZZLE end can be anything from a svelte taper, to a full 1 inch dia bull barrel.More if a flash hider/ muzzle brake is attached.

[Grumpy]

"However, can someone tell me if the 'Rifling' (or the 'grooves' which make the trajectory spin) is cut or is projected?"

TenX, by `projected` I presume you are asking if the rifling lands can be built up ? If so, the answer is `no`...................... I can`t even think how that might be done. Otherwise see Mack The Knifes answer above.

[biking3819]

i think an electrochemical process also exists to do rifling,not sure about it being efficient though.
i read it somewhere cant recall the link now.,if such a process was present then is it possible to built lands?
regards sanjiv

[Grumpy]

Yes, you`re right, rifling can also be `cut` using electro-mechanical process however that`s still `cutting`, just using a different technique. Technically I suppose a similar technique might be able to be used in order to build up the lands but I`m pretty certain no-one does.......and can think of no good reason for wanting to do so.