I have a PSL, many Mosins, a Mauser and a Tokarev pistol that I shoot nothing but corrosive ammo .
Never had any rust problems .
I use 5/1 Ballastol, water mix in a spray bottle.
Before leaving the range, while the gun is still warm I soak down the bolt face and the bore. Followed by a bore...
I was at the N.O. gun show just a couple weeks ago an was surprised how many "non ammo" tables had 22 ammo.
No other ammo, just 22LR at 3-4 times normal price.
One thing to look out for is soil erosion below the slab. It can cause cracks in the concrete. I had a hot water leak in the slab itself that I fixed myself. It was a pain, but I saved a ton of money. I was lucky the plastic between the slab an the soil prevented any erosion problems.