16 ga shells? Not that common, and certainly not cheap.
AAAAH! Again with the myths. IF you mean "not that common" that a small gunshop or the yahoos at Wally World don't have them, you are correct. OTHERWISE, They are easily ordered online from Sportsmansguide. If you only shoot a box or two a year, and might forget them, and have to rely on the local skeet range to have them, then the 20 gauge is the way to go.
Additional myths I have also heard...,
They are all foreign made shells, Estate brand shells are made in USA, and Remington, Winchester, and Federal are still making shells for that gauge, including waterfowl and slugs.
As for price, they are slightly more expensive in some but not all loadings than 20 gauge. If you buy in bulk even with shipping they are often not more than a dollar more a box, so unless you are shooting a flat a month, you're not saving much money with a 20. I have mentioned in the past on other threads that when you find "sales" on bulk shells, you WILL save more with the 20 gauge, but again, you need to buy lots to see the savings.
AH HA!
You guys missed that the shotguns belonged to his grandad, which probably indicates ONLY 2 & 3/4 inch shells, which really reduces the available variations in ammo for the 20 and adds a slight argument for the 16. For with the shorter shells, the 16 does do more than the 20..., of course if Grandad bought the wingmasters with 3" chambers, my clever argument goes miserably down in flames !
NOW I love 16 gauge for nostalgic reasons, but must point out the simple fact that if you forget your shells at home, you have a better chance at finding 20 gauge shells at any mom-n-pop gunshop or at the range, than 16 gauge.
Me, I use a SxS and I have chamber adapters so I can shoot either 16 or 20 gauge shells from my 16 gauge guns. So I can do either, and IF I have a problem with 16 ammo, I can find and use 20 gauge as well.
LD