As my moniker would suggest I have an interest in the 4 bore rifles. I had a true 6 bore that was smooth bore round ball gun. Although limited in this in my practical experience, Ive done a lot of looking and fair amount of reading. And sadly maybe forgetting too.

I consider the "TRUE" four bores to be any guns that fired 1/4 oz projectile. Thats today. But we used to call them 5 or 6 and no shame or denigration implied. In most cases just the opposite. I guess the commercial reality had lead to referring too all the over 8's as being 4 bore.

And in my opinion (and just an opinion) the 'best of the best' so-called (today) 4bore were all proofed as 5 or 6 and fired conical ~1/4 ounce bullets behind the heaviest charges of black power. And for the few who could handle them they were the best killers, prior to cordite.

All the 1 inch guns I ever saw or read about fired 1/4 ounce round balls and were the biggest (bore diameter) guns actually used with any success and built in any numbers in excess or 1-zee or 2-zee experiments. I hear a few guns were made to fire 1 inch conical bullets but yet to see in person or even a photograph a single example. I hear there was a new book, I need to find a copy.

I suspect 150 years ago as today we had odd ball exceptions and experiments. Wierd stuff happens, like terminator II fantasy weapons. Someone today or yesterday build this or that but the guns were really hunted and called four bore, were generally proofed as 5 or 6 and those were the great guns of yesterday. Those and the round ball 4-bores the biggest bore, if not the best.

Thats my take on the past, and what happens in modern time is a separate subject. Anyway was not just 4 and 8, it is 4,5,6,7,8 with a lot of those .9xx bores that were the true greats of the past.

Two bore, I dont think so. Only as a modern fantasy piece, like the 700.