I tried the 16 ga guns years ago. Never impressed me much. Most 16's were made on 12 ga frames except some of the older doubles. Early 1100 and 870 guns used the 12 ga frame for 12 16 and 20. They did lighten the bbls though. After a couple hundred thousand 20 ga shells I figure I can do anything with it that the 16 will do and ammo and cases are much easier to find. Used to use it to shoot duckies with too. till the steel shot thingie(what a crock). Now withthe hevi shot etc etc out there I'm going back to the 20. I must admit though you guys are right with the lack of ammo for the 16. Last 16 I had was a Valmet O/U I got at a yard sale. Got 8 boxes of SuperXX 16 ga 2s with it. Sold the gun and still have the shells. Shot a couple of Pheasants with it.. Those XX Win shells sure let ya know in that little Valmet. I'll take those ol shells to another gun show one day and trade 'em fer something useable.
Now as to the 6mm.. I have just purchased a really nice 700 BDL Varmint gun in 6mm. Got it for 400 bucks and it's like new(kinda yard sale find). Guy has a matching gun in 22-250. Might even buy it. Has a Ruger #3 in 22 Hornet for sale too. Also has a Ruger 44 mag semi auto carbine. Price is a little high but may have to buy it. I happen to like the 6mm Rem as it shoots a bit faster than the 243 and seems to be a little more versatile..Have many once fired cases in 6mm as well as a few boxes of ammo.. Y'all can have yer 16s. Make mine a 20. 1 oz 16 or 1 oz 20...what's the diff....except I can find 20 ga ammo MUCH MUCH easier. And most guns in 20 ga ARE built on a lighter smaller frame now days.