We have a bolt action conversion on a AR lower (the now discontinued BOHICA). We were shooting at large bus cast iron brake drums (super thick) at 250 yds. The FMJ steel cored bullets went right through the one side, hit the other side and spun around inside the drum. We were able to retrieve one. The power is massive.
California outlawed the sale of 50BMG rifles so we got the BOHICA in 50DTC. It is the 50BMG case shortened 0.1 inch and the shoulder set back a small amount. The barrel is marked 50DTC so it is CA legal. The down side is you have to trim the 50BMG cases and fire form them but I have done about 100 and none have split. The fire forming load is just a 50DTC starting load. We continue to use that same load on fire formed reloads as it is more than enough for us. Our desert shooting spot is limited to about 800 yds and we are working towards shooting metal targets at that range.
I was able to pick up some scrap metal plates at a recycling center. I got a 16"x21" steel plate 1/2" thick for $8 out the door. 1 of the guys working there choping stuff up with the torch actually torched out a standard size IPSC target 1/2" thick (way stronger steel too) for me. I hooked him up with a tip, he wasn't even expecting anything so that was cool. And I paid $15 at the counter for the steel, it was 75 lbs so it worked out to .20 a pound. Just an option to try to score cheap steel. I have a hard time forking out $250 for an IPSC target online.
Over the years I have had many steel targets of various thicknesses (one was actually one inch thick). Even the tiny 223 makes a mess out of steel targets. If the bullets don't go through them, they upset the surface so bad that they are a danger to shoot at much closer than 100 yds with anything. They all suffer badly when shot with any rifle round if made of mild steel.
The only one that is surviving is the armor plate one. It is not all that thick but just very hard. It is AR500 steel. Regular hunting rounds (like 30-06) barely mar the surface at 200 yards. But indeed that target was expensive. We picked up another AR500 target for shooting the 50 cal at 800 and 500 yards. We'll see how it does. Unfortunately, the inexpensive 50 cal bullets I use are steel core which is hard on steel targets.
Oh yeah those steel cores do some damage. I recently made a youtube video shooting one of my steel plates at 1200 yards with regular ball ammo, put a decent dent in it still. I usually shoot around 300 yards at the mild steel with the ak, 400 and more with the .308. Any closer it really does gouge up the metal. But hey long range is my passion so I can get away with it for now. Id just hope my IPSC target holds up to the .338 lapua and the 50 bmg at 1 mile. If not I'll be going the AR500 route.
They had a KABOOM (thought to not be the gun's problem but a reloading problem by the shooter) and the lawyers attacked. The company left California and re-appeared under a new name (sorry I don't remember the name???) in Nevada, I think it was. They showed up at a gun show there, as I remember it, in the last year.
So if you scope out the internet you may be able to find them under AR conversion or 50 BMG or ???
There is nothing wrong with our BOHICA although there have been many complaints by others who got earlier version. Ours was the last CA legal 50 CAL (50 DTC) as we had to plead with them to make one more in 50DTC and sign a waiver (leagally protecting them if anything happened which we gladly signed after spending a fortune getting a reloading setup for 50 DTC that would have to have been abandoned if we could not get a 50 DTC gun after the KABOOM in LA).