Daryl has always done much better than me with round balls, and we have been 'round this buoy on these forums before!

Nevertheless, permit me to retell my earlier experiences here, if only for a laugh!

About 20 years ago I decided to experiment with round balls in the 12-bore. I started with pure lead 12-bore balls from the muzzle-loading suppliers, but quickly learned that they deform in the bore on firing, and fly all over the place. Shooting 16-bore pure lead balls in a 12-bore shot-cup was the next step, however results were just as bad.

Then I got the notion that solid steel balls would not deform (!), so I obtained a couple dozen polished steel ball bearings from the mob that rebuild automotive CV-joints, and loaded them up in AA-wads and shot them out of a cylinder-bore double I had lying around. Here is the result:

The two high ones were from the clean, slightly oily (?) barrel, the remainder went into about 3 1/2 inches, at 25 yards!

Turns out the wad was trying to crawl past the ball in the bore, pushing the ball off line before it exited the muzzle. Check out the recovered wads, very uneven damage to the shot-cup petals. Some petals were chopped off completely!

So...! The next step was to try to center the ball in the shot-cup. I cut the over-powder part off a few 16-bore wads, inverted them in the bottom of the 12-bore shot-cup, and dropped the ball-bearing on top. The results improved slightly to 2 1/2 inches for 6 shots (3R + 3L), still not brilliant for 25 yards.

At least this time, the impressions on the wad petals were even all round (and none were chopped off!), showing that the ball-bearing remained centred in the bore.

At that point I gave up, assuming that no better than 2 1/2 inch groups at 25 yards (5-inches at 50 yds, 10-inches at 100 yards) could be obtained from a round ball under any circumstances.

Always happy to be proven wrong at any time, though!

...and please don't burr up telling me it was dangerous to shoot hardened steel ball bearings in pommie shotguns. I already know I'm a little crazy, but with enough common sense (or blind luck!) to have survived thus far!

After giving up on round balls, and suffering through some very unhappy experiences with the RC4 Palla slugs, I discovered the Rio Bala Blindada and killed a few boars, and a full-grown buffalo cow with one shot, for some degree of vindication.
Read about it here if you have the time.

All this was because our importers won't bring Rottweil Brennekes into Australia, and now the Rio Bala Blindada is no longer available! The flat of ammo I ordered never arrived! Only one box of 10 left... (sigh)

So like others here, I am now concentrating on the Nitro Paradox option, as I probably should have been doing all along!