I used to shoot clays at a private shoot on a farm. Which changed hands. The new owner decided to go organic and specialise in rare breed cattle, but was very keen to keep the shoot. When the Soil Association inspected it, they were insistent that we stop shooting with lead because inevitably the cattle would ingest some shot, and unlike humans, absorb it whilst chewing the cud. We had already been using only fibre wads, to avoid any problems of the cattle eating them.
So we had to find an affordable lead free fibre wad alternative, fortunately there was one (only one), Gamebore Super Steel competition load 24gms 7.5 steel shot with a fibre shot cup which they claimed could be used in any gun, steel proofed or not, providing half choke or wider, due to the thick fibre cup that that totally enclosed the shot so it never touched the barrel. It was also loaded in transparent cases so you could see if the shot had gone rusty in improper storage. Very well thought through.
We had to order it in sufficient quantity to last our season, I think they only did a run a few times/year. Some years later they discontinued it in the fibre shot cup version, presumably lack of demand for this specialised load, so the shoot had to close. Prior to this the club ammo was Gamebore Blue Diamond 28 g lead, fibre wad, or whatever else in fibre wad. No the Super steel at first seemed not as good as the lead, so we had to adjust the trap layouts initially, but as we got used to it and adjusted our leads we found that we could shoot it almost as well. And it put us all on a level playing field, which was good. They patterned well (lots more pellets than lead, for the same mass) Also it was slightly less expensive !
In the interests of science, one of the members even put a box through a beautiful old damascus barrelled piece, to no apparent detriment.
AFAIK there is still no steel ammo with fibre wad available in the UK. The focus seems to be on "biodegradable" eco wads, which are not suitable. Until they have actually degraded in weeks or months ? they still pose the same danger to the cattle as plastic and litter the ground.
Such a shame that Gamebore did not develop this line with fibre cups for any old gun, but I see no reason why ordinary fibre wads could not be used in a steel proofed gun with suitably durable barrels.
The cups are still available from ClayGame for reloaders, 12 gauge only, but AFAIK not in factory ammo.
Fiber Shot Cups for use with Steel Shot, to manufacture full Bio safe shotgun cartridges.
www.claygame.co.uk
Also steel shot is not AFAIK not manufactured in the UK, ISTR that it mostly comes from France, and there can be supply issues, which I suppose will only get worse unless production capacity is increased. Then there are the CIP regulations, which limit the velocity and momentum of CIP nations' ammo to rather anaemic levels compared to what is available in other territories and has been used safely for many years. This needs to be reviewed.
I think that there is a long way to go before BASC's "voluntary" lead phaseout for shotgun cartridges becomes practical for all uses, no matter what they might have been led to believe by UK manufacturers. And IMO the degradable eco wads are not a substitute for fibre. Personally I will not use plastic wads of any description unless there is no choice.