No idea on size of specific sinkers, but you can "embiggen" one by putting it on a hard surface (such as the 'table' on the back of the usual bench vise) and giving it a few whacks with a hammer. Might save a trip to the store to buy something else.
If they're real lead, the vice or the hammer will work. If they're the oddball alloy fishing sinkers sold in the big box stores around here, they will be too hard, which means they wouldn't have worked for bore slugging anyway. You need pure lead.
If you look at fishing sinker charts, the sizes refer to weight rather than physical size. That will let the makers choose different alloys of different densities. At a guess, a round ball that just is pure lead and is about 0.002" oversize for slugging, would weigh about 1/3 of an ounce or about 146 grains. If we assume the egg sinker is an ellipsoid twice as long as it is wide, then it will weigh just twice that, or about 2/3 of an ounce or about 290 grains. Actual sinkers might not be perfectly pure and weigh slightly less, but that's the ballpark.
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