- But way back in the 1840/50s there was a cap'n'ball calibre known as the .31" which later developed into the .32" centre fire calibre cartridge - by way of some early rim fire cartridges.
Early 'Dished Base' .32" Calibre Rim-Fire Cartridges.
- But you should know that those .31" percussion revolvers - which were known as "Baby Patersons / Baby Dragoons" - used conical bullets and balls that measured .32".
- These "Babies" grew to become the likes of "Colts Revolving POCKET Pistols" around the 1850 mark.
Nowadays we have logically sorted-out all that confusion (not) and now we have the excellent:
327 Federal Magnum uses .312" diameter bullets
- this is a lengthened, strengthened and up-powered .. (with an internal pressure ceiling 45,000 p.s.i.)
Here is a good place to note that the 32 ACP is a semi-rimmed cartridge firing a .312" bullet and can be fired safely in your Ruger SP101 327 Federal Magnum revolver - That makes five different cartridges that you can use in this 327 Federal Magnum calibre gun.
32 ACP semi-rimmed Pistol Cartridge.______________
Then again - Do not try that with the similar but different:
(- Which is/was a lengthened .32" Short Colt.)
WARNING Those will not be confused with the different again 32-20:
Confused? - even the bloody drawings disagree - is the 32-20 rim thickness .60" or is it .65" ? - The 32-20 (aka .32 WCF) used a .312" diameter bullet in front of a 20 grains of black-powder. - But it is really obsolete now as the 327 Federal Magnum is much stronger with superior performance.
32-20 Blues. Eric Clapton- I knew that I shouldn't try to sort this out.
- Did you notice that I haven't even mentioned the .320" Revolver round - aka. the .320 Webley or Bulldog that uses a .317" bullet? - Nor the 7.5mm Swiss Army that also used a .317 projectile. - or the 8mm Gasser (.320"), 8mm Nambu (.320"), .32 Winchester Self Loading (.321" bullet), nor the 8mm Lebel Revolver (.323").
- All that I am trying to say is that when you get into target / sport shooting and gun collecting you do need to be careful to make sure that you put the right cartridges or bullets into the right chambers.
- or you might achieve what is known in the trade as a 'KABOOM'.
So the old .31"s used .32" diameter balls - and the .32"s use smaller .312 or .314" or .315" dia pills! - Is that clear?
Some dimensional differences can be explained by 'tolerance' - allowable manufacturing variation - while there is certainly some limited tolerance in projectile sizes - as a slightly smaller bullet may /will 'set-up' and expand into the bore under the propellant gas pressure and a slightly oversize soft pill may squeeze down to calibre while causing some increase in internal pressures. DO NOT TRY THIS.
- Now, to the .32" semi-auto pistol calibres (such as the .32 ACP (Bullet diameter .3125").. I'm really not going to go there - except to observe that it's not only the old dated designs such as the .35 S&W of 1912 to be considered (that uses a .319" calibre bullet) - but we have much more recently in 2002 - the .32NAA that is a .380ACP necked down to use a .32" calibre (.313") bullet..