Completed a casting mold today. It will go to Jerry to add a fine 8mm Bishop to the slug group. This will size between .3125" and .315" (which is actually 8mm). As I've detailed before, much of it is in picking a name to call the caliber. Few bullet calibers are actually true to the numbers.

My early series of barrels for the Prairie, Prairie 2, and a bunch of guns called 32 caliber, were liking the .313-.316 size (depending upon which slug). The middle series of 32's (the Ranger Delta Series) were for the .318" size range. I call this revisited series of barrels 8mm (which they actually are BTW) ... to distinguish between the different generations.



This test cast very well.

Gary

There's nothing like a nice, long, technical discussion of calibers versus actual bore and projectile diameters to add confusion to an otherwise inpenetrably dense and complicated argument, is there?

Yes ... I think one of the most obvious screw ups is calling the .358" to be a 38 caliber. Pretty huge "rounding error" there.

It's 35 caliber! No, it's 9mm! No, it's 38 caliber!!!

hehe

Gary

Hi Garry, the original .38's had what they call a heal type slug that stepped down to fit inside the case.The 38x55 for eg had an OA of .377 (case and slug) with a .010'' wall thickness to the case. Somewhere along the way someone had the bright idea of shortening the case and casting a slug that would fit inside without the step, ie .357 (which is the .38 special) and of course latter on the .38 special case was extended by an eighth of an inch and more powder added to make the .357 magnum.They extended the case simply to stop people trying to load .357 magnums into guns that were'nt built to take the extra chamber preasures, you can load 38 special cases to .357 magnum loads no problem(although it isn't recomended(some poor bugger may accidently load one into a 38 special and do some damage).Having said that you can load 38 special rounds into a .357 magnum.Now with the 8mm Mauser like a lot of European and commonwealth countries they take the calibre measurement at what they call the over the lands (which is the smaller PCD) which as you have said is aprox .315''.The original 8mm Mauser Had .003'' of lands OA, yep only one and a half thou deep making the slug .318.Some time later on they deepend the grooves to the standard .004'' each which bought the OA out to the current .323'' which is called the 8mm js.The .303 British has an over the lands measurement of .303 as the name suggests with .004'' deep grooves which brings it to .311 as the commonwealth built .303;s are.The Canadian and US built .303's have an OA of .312'' for some reason,I reloaded some rounds for my SMLE .303 a while back useing some Hornady .312'' Projectiles and expearienced some higher preasures as a result(my barrel being .311'' OA. Nothing dangerouse just flattening out the primers big time, and with a rear locking action you have to be more vigelent.You are right though Garry often the calibre is simply a reference and you have to make double sure you've got the right round/ slug for the gun.Danny.