Steel shot:
Most (although not all) current production shotguns will be equipped with screw-in chokes and/or generally compatible with steel ammo. Firearm manufacturers will usually state the same in their product literature. Moreover, many brands will also stamp choke tubes to indicate what may or may not be compatible for use with steel ammo.
There are also older model shotguns (with fixed chokes) in existence that may be made compatible for use with steel ammo. In such cases, normally a gunsmith may need to ream out an existing tight choke in order to convert that to a more open choke that is suitable for steel shot.
Bottom line, if you are faced with uncertainty when selecting a shotgun – don’t be reluctant to pose all relevant questions at the store/seller regarding the firearm.
I really think we need a "myth busters" episode on modern (i.e. nitro-proofed) steel-barrelled (not damascus) shotguns and steel shot performance.
For starters, there is the patterning issue. As a rule of thumb, go one step more "open" for steel shot to pattern the (roughly) same diameter as lead. For example, a lead full choke will pattern pretty close to steel through a modified choke.
Now we look at older fixed choke guns. When steel shot came out, all the manufacturers put out literature that you needed to buy a new gun certified compatible with steel in order to shoot steel shot safely. A LOT of guns got sold this way. It tended to coincide, more or less, with the introduction of threaded choke tubes.
Now here's where a Mythbusters theme comes in. The manufacturers had a LOT to gain by convincing you the gear you've been running is no longer good enough. I remember this time well, I was big into duck hunting back then, and there was a TON of handwaving. My brother used an old Stevens 320 with a fixed full choke, and I was running a Winchester Model 1400 at the time. Mine was deemed "compatible", his was not. The old 1400 was a POS that always jammed with high-brass shells and only liked the cheap stuff, but that is another story. The bottom line is we just switched to steel and shot the guns as they were. Nothing bad happened and nobody's d!ck fell off. These were regular 2,3/4" steel loads, not high-velocity or "high performance" magnums or anything.
I hear this story over and over that older guns are "no good for steel". One of my friends is a (nameless) gunsmith of some repute. According to him, he's NEVER seen barrel damaged by steel shot use ULNESS it was a modern screw-in choke gun. And even then, it's typically when guys are using FULL (or tighter) chokes with ammo larger than BB. (which is stupid behaviour, but that's beside the point). I've been around a lot and I've yet to see an older gun ruined by steel shot using typical duck loads. Even BB and larger seems to do well through fixed modified chokes. As a general rule, I only shoot steel through modified or more open chokes, out of an abundance of caution. YMMV.
Show of hands - anyone here seen an older "modern" gun ruined by steel shot first hand?
By the way, Remington may be perhaps the least conservative of the older manufacturers in their recommendations as follows:
We do not recommend the use of steel shot through any barrel manufactured before 1963 or through any barrel having a fixed Full choke. Anything larger would not perform well out of a fixed full choke and could open up your muzzle over time.
If you have barrels manufactured after 1963, with fixed Modified or Improved Cylinder chokes, you may shoot up to size #2 steel shot. The use of steel shot larger than size #2 is only recommended in modern barrels with the Rem Choke system.
If you have the Rem Choke system, you may shoot any size steel through the Improved Cylinder and Modified choke tubes. The Full choke tube must state "For Steel or Lead" to be capable of handling steel shot.
Not sure why they picked 1963, but it's possible they changed steels or something at that point.