You are not limited to vintage guns. There are modern, fluid steel guns available from Beretta/MiVal, Bernardelli, SIACE, and others including, I think, Huglu. I have a couple of fluid steel Bernardelli Brescia hammer guns in 12 ga that cost me only $1K each and will shoot any modern 2-3/4" lead load. If I open the chokes, they will be fine for steel. There is also the Bernardelli Italia (same gun with more engraving and nicer finish). SIACE guns tend to be more expensive, but they are readily available on the used market. Ivory Beads officially closed yesterday, but they will still probably answer the phone. They had a Beretta/MiVal 12 hammer gun last week and it may still be available. Somebody on ShotgunWorld was trying to sell a Bernardelli Brescia 20 ga a couple of months ago, and that one may still be available.
Parker hammer Damascus guns tend to be fairly stout, and there are plenty around; mine was $1k a few years ago. There are also plenty of unrecognized Brit (mostly Birmingham) and Belgian guns out there with laminated, twist and Damascus barrels available at decent prices, but buy those from someone you trust, unless you are able to inspect before purchase. You also don't need to spend the money on RST and other boutique low pressure loads, because companies like Fiocchi and B&P have a line of low pressure loads at very competitive prices. My Brit laminated steel 12 likes the Fiocchi 7/8 oz training loads that are very low pressure (6100 I think, but don't remember for sure); these are available over the counter at my local sporting goods store.
Another alternative would be to buy a 10 gauge and shoot 12 ga loads with ChamberMates. Could save you some money on the initial purchase and allow use of WallyWorld ammo if the gun is tight.
