I have a 1960 IZH 54 SXS. Biakals even at that time have chrome bores;really well built guns However, your chokes are too tight for steel, tungsten, heavishot etc. I have shot steel in a sxs Uggie with chokes sk 1 and sk 2 with no problem.www.rstshells.com
has "Nice shot" cartridges that out perform Bismuth and can be used in any choke that lead can be used in. But they are $75.00 for box of 25; a little cheaper than Bismuth or Heavishot Classic.
Keep an eye on www.ballisticproducts.com
though, they have come out with ITX non-tox shot that is a very good performer at lower cost and can be used in guns choked for lead. In a couple months, they may have loaded cartridges for sale.