Looking for info

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The Croc

Well-Known Member
I know/recognise most calibres up to 243, but over that I start to get lost
ie I know that
223 = 5.56
308 =7.62 (7.62 x51???)

could there be a list of calibres in imperial with metric equivalents going up in size or could someone/anyone put up a list

243 =
= 6.5x55
308 = 7.62


thanks for any info


Little Terry

Well-Known Member

Unfortunately I think it a little more comlicated than that. Many metric calibres have similar imperial equivalents, but often they are only that.

Further complications occur when comparing the different projectile weights available for various calibres. Simply by looking at some of the other threads on here, you will see just how involved it can get!

I'm no expert, that's just how I see it. Maybe someone else could shed more light on the matter???

I would certainly be interested too...........



Well-Known Member
The Chuck Hawkes site contains some useful information although as on any site where there is more than one contributor there are differences of views on many subjects. All the better for it in my opinion.

Also have a look at various reloading manuals. They generally give a synopsis of the caliber and its uses, whether it is similar or identical to another caliber also detailed descriptions of the cartridge case, the suitable primers, the various bullets including their suitability for various tasks as well as the different types powders for loading the completed cartridge. Typical presures and speeds are also quoted.

Even if you never take up reloading they also open the door into a world of discussion on what caliber will do which job best or how one caliber is 'better or worse than another caliber', as can be seen by reading various threads on the forum. However if you compare the various manuals you will find that they also differ in their recommended loads for different calibers.

How to choose which manual to 'believe'? Pick one and stick with it until you feel you have gained experience to change direction.

Here endeth the lecture and enjoy the investigations.


The Croc

Well-Known Member
Thanks folks that will get me started/confused, as in airguns the circular discussion on 177 v 22

Now if someone could tell me the best and definitive alround calibre for for Stalking ;) :lol: :lol:



Well-Known Member
I used to own a wildcat .355 express what an animal that was :lol: we had to machine cases out of brass bar or you could use cut down .303 cases to make "shorts" we used to shoot rabbis with it for fun when we were younger with devastating effect :evil:


Well-Known Member
The Croc said:
Anybody got any info??

Here are some of the common ones off the top of my head this relates to bore size only.








Best rgds



Well-Known Member
6.5 is a strange one as it converts to .256 but actually fires a .264" bullet

here is a table of calibres with bore and groove diameters

Caliber__________Bore Diameter_____Groove Diameter
5.56mm/22 CF______.218/.219 __________.224

As can be seen from this list there is no system as to whether the bore or the groove dia is used.

6BR (Bore Dia) 243win (Groove Dia)
.257 Roberts (Groove Dia) .25-06 (bore Dia)
6.5x55 (Bore Dia) 264win mag(Groove Dia)
7mm neither bore nor groove
300win mag (Bore Dia) 308win (Groove Dia)


Distinguished Member
The Croc, do you call yourself this because you are trying to get people to bite?
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