I've reloaded steel cases a couple times just to see if it is possible. It is possible The biggest issue is a lot of times steel cased ammo uses berdan priming which uses 2 off-center flash holes, which means you'll get a bent/broken de-priming pin if you don't catch it. There are, however...
A lot of times the steel cased ammo coming from eastern block countries also had copper washed steel jacketed projectiles. When those hit a steel backstop, they can spark creating a fire hazard. A lot of indoor ranges use a backstop system that consists of angled steel plates covered with...
M855 actually has a mild steel core sitting on top of a lead core, with a regular copper jacket. The purpose of the mild steel cores is to keep the weight down and the balance (center of gravity) where it needs to be for best performance.
The bimetal stuff is steel jacket with lead core...
There's also a matter of what is called a bi-metal jacket. A good bit of the eastern european (and some western) ammo has a mild steel jacket and a copper wash. So it looks like copper, but is basically steel. That's why they use a magnet on the bullet. Steel jacketed ammo can spark when it...
I guess the deer (and other targets) never complained about it.
And the more I think about it, it only really effects long range in flight dynamics. They say that the meplat become progressively larger, increasing drag. However it seems like the bigger issue was that the BC was changing in...