Are .30 & .303 interchangeable caliber?

Was reading about .303/.30 cal just yesterday. All that I could glean is that Daystate calls their .30 cal guns .303 as it is traditional British. Metric equivalent of .303 cal would be 7.7mm. But look at the Daystate .303 ammo: Specified as 7.62 mm, or the same as .30 cal. My understanding is that you can shoot .30 cal in a Daystate .303 gun, and Daystate .303 pellets in a .30 cal gun.

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30 caliber is actually .308 or 7.62 mm where english caliber 303 is .303. 

You could shoot the .303 in a .308 but it would not be very accurate. If you put a .308 in a .303 it would not go in.If you forced it. It would get stuck.

I don’t want to sound like a know it all, but this is not entirely correct. Oddly, if you were to load for the British .303, you would be using bullets that were .311 or .312 in diameter.

Your last statement is actually opposite of what would happen. The .308 bullet would work in the 303 bore, albeit as a loose fit. It would almost certainly obterate to fill the bore, but it is not what you would do if you were looking for the best performance out of a rifle. And though you could probably get away with it, a .311 bullet in a .308 bore might be courting trouble.

l suspect that as far as airguns go, the .30 or .303 designation is merely a case of semantics.
 
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