Stupid question:

Is it legal to have steel jacket or steel core ammo? I'm confused by this topic. I understant M855/SS109 are not considered AP. S&B makes SS109 that is a steel jacket with guilding metal--and this isn't AP, yet by BATFE's description, it is if you're talking about true SS109, and not steel jacket. Their definition seems to include everything, except SS109 and M2.

A local range forbids use of AP and other steel jacket/core ammo. Some of the surplus rifle ammo I have has a magnetic projectile--honestly I don't know whether it is steel jacket or steel core or AP or what--it was cheap and frankly, I'm annoyed if I can't shoot it. Fortunately, I can always shoot it on a friend's property.

Any takers on this? Obviously, not looking for legal advise.

Usually steel jacketed ammo is not AP ammo. A very mild steel (you could basically talk about iron here) is used, which when covered by gilding metal isnt even more harmful to barrels as is pure giliding metal jacket ammo.
Ammo like 7.62x39 often has an iron core to save lead (its cheaper to produce). Those bullets, due to its soft core, dont qualify as AP ammo either.
It comes down to what you local range allows. Their arguments are usually target longetivity.
So by law youre allowed to shoot steel jacketed ammo, or iron cored ammo (as long as its not hardened steel as in AP rounds. 7.62x39 is NOT hardened steel in normal "ball" ammo).
BUT you local range might exclude ironcore/steeljacket ammo for saftey/financial reaons (erosion of steel targets).

So a mild steel jacket, or core, doesn't mean "armor piercing?"

If you read the BATFE explanantion, they make it sound like everything that is steel is AP, except for .30-06 M2 (which actually is AP) and SS109.

Mild steel jackets are pretty common in ammunitions from eastern Europe, its just a cheap substitute for gilding metal or copper. Mild steel cores are used in some ammunitions for the same reason (lead substitute), like in military 7.62x39 ball.
They are not AP ammo!

[edit] I am not 100% sure how (iron cored) 7.62x39 handled by law in this case. Someone wants to chime in?
By technical definition it is not AP though.