I do not know of any ammo makers that still load ANY round ball shotgun loads. However, there ARE 28 gauge slugs (Brenneke makes them) that are available. An internet search using the term "28 gauge slug ammo" will show several companies that carry them. They are about $11/ 5 shells plus shipping cost, so they are not cheap.
Think of a lead ball which is the diameter of the inside of the barrel of the shotgun. The gauge of the shotgun is the number of balls that size to make up one pound. 12 balls - 12 gauge 20 balls - 20 gauge 28 balls - 28 gauge Exception - .410 bore is the actual bore diameter
Shotgun gauges are determined by the number of lead balls of a given diameter required to make one pound of that size ball. Thus 10 balls of 10 gauge diameter are required to make one pound of such balls, or 20 balls of 20 gauge diameter are required to make one pound, and so forth. This is the traditional, and very old, system. The actual (nominal) bore diameters of the various gauges are as follows: 10 gauge = .775 inch, 12 gauge = .729 inch, 16 gauge = .662 inch, 20 gauge = .615 inch, 28 gauge = .550 inch. The .410 is named for its nominal bore size, and is not a gauge at all.
28 oz
A 12 gauge shotgun is determined by the fact that 12 solid balls of lead will fit into the bore of the gun and thus these 12 solid balls of lead will equal a pound. Likewise, it takes 20 solid balls of lead fitting into the barrel of a 20 gauge shotgun to equal a pound. 10 solid balls of lead that equal a pound fitting in the bore of a shotgun would make that a 10 gauge, like wise a 16 gauge and a 28 gauge. There have been 8 gauge guns but an exception to all this is the 410 which is not a gauge but a caliber. The caliber of a 410 shotgun is .410 or there a bouts. Some research on your part will help you understand more if your desire but you can see that smaller balls make gauges with larger numbers and therefore, a larger number gauge like 20 will shoot shells that are smaller in diameter than those shot in a 12 gauge.
26
20 gauge is larger
.410 bore is .410 inches 28 gauge is .550 inches 20 gauge is .615 inches 16 gauge is .662 inches 12 gauge is .729 inches 10 gauge is . 775 inches
A Pardner 28 gauge single shot cost is 110.00 to 130.00 A Pardner 28 gauge single shot cost is 110.00 to 130.00
28 gauge with single barrel How do you find its age and value?
1-2 days at 28 degrees
value of a harringtonand richardson 1900 28 gauge
12, 16, 20, 28 gauge and .410 bore. The 28 gauge is most rare, worth three to five times the value of the 12 gauge