Ballistic products is know to extrapolate data. Meaning they don't actually even put the loads together and test them, just think they know where pressure will be.
I'd be very careful using their information, seems like you can't get half their loads to even fit.
Reloading Specialty (RSI) and Precision Reloading have steel loading data.
Be very careful working with shotshell's if you are use to metallic. You don't work up loads, they are all relatively low pressure and you don't get pressure signs before it's dangerous. Don't substitute. Reload using trusted data and replicate exactly. Also be aware that older loading data using Steel powder are likely over pressure. Steel powder isn't always consistent from lot to lot and after the first few years of its production it seemed to get hotter. Check your loads with a chrono, if they are running faster than they are supposed to, you know they are higher pressure.
In my opinion it's hard to justify loading Steel in 12 ga. Or even 20. I load Steel for 10, because everyone makes those loads soft. 12, 20, and 28 I load heavier than lead stuff, or just buy Steel loads.
I agree. I loaded steel shot for close to 10 years, but it really only made sense for the first 5. By the late 2000's steel shot factory loads were as effective as they ever will be, and prices too low to be competitive with reloads. 10 gauge as you say you can load for better performance, 16 gauge you can too.
I think it was about 2015 I started playing with bismuth shot. Before this I had tried tungsten based shots in factory loads, but the cost never has become reasonable to me. Even back then it was around $75 per box to load hevishot. Factory hevishot, the real stuff not the scam loads, was ballpark $50 for 10 rounds. I first bought my bismuth shot, and started playing with loads. I quickly found success, not just any success, but I absolutely blew steel shot out of the water. I started making my own bismuth shot, and did for a number of years, but it kind of died off for me as bismuth shot can be bought for a reasonable price now. At the time I bought 200 pounds of pure bismuth, and got a smoking deal on tin. Today I doubt you could find such a deal. It's not that hard of work making shot, but it does take up a weekend. Over the years Rotometals has both improved their process, and kept the cost of their shot just about the same. Even after 2020 crazy inflation, their prices today are only around $10 more a bag than they were in 2015 from what I remember. By comparison bismuth shot has never been cheaper, so it does not make sense to make it anymore. Ballistic Products also carries bismuth shot which is tin plated. Comparing them side by side I think the tin plating is a complete waste of time. I believe Rotometals makes the shot for BPI, and the shot roundness is the same for both plated or not. Patterns are unaffected. Prices are similar, so no real reason to shy away from the tin plated shot. Shipping is free from Rotometals, but if you are already placing a BPI order, it might make sense to buy their shot.
What I found with bismuth is that it is very similar to lead. What makes lead tick, also makes bismuth tick. That is moderate or low velocity and buffer being the two biggest factors to getting the tightest patterns you can. You can certainly use bismuth without buffer, I've even used a bunch of it in muzzleloaders, you simply won't get the tightest patterns you can that way. Forget all that 1350+ fps nonsense, that's just blowing money out the end of your barrel, and paying a second time with your shoulder. 1300 fps and under is your wheelhouse. Bismuth works great subsonic too if you are into suppressors. For shot size, I found 1 size up from lead provides about the same penetration. For example a #4 bismuth is about like a #5 lead both equal velocity. For ducks I find a #4 works best most of the time. I think a #5 could work good if you shoot mostly smaller ducks, or maybe small gauges like 28 gauge. Even a 20 gauge I think a #4 is better most of the time, again unless you are shooting mostly teal and woodies. I found no success with #6. It killed birds, but it runs out of penetration way before the pattern does. I do not count head shots as good hits, I only use shot size that will go through a breast and into organs. A #3 can also be a good choice if you are shooting some heavy 12 or 10 gauge loads where you can get enough pellet count for it to matter. My heavy 12 gauge load is 1 5/8oz shot, and I think #3 is a better option there. My typical 1 1/4 oz load #4 is the superior choice. In 10 gauge with the 2 ounce load, use #3 for sure.
Most of my best loads have come from Tom Rosters Buffered Lead and Bismuth loading manual, and his newer Advanced Lead and Bismuth loading manual. I also have found one or two really good ones from Lymans 5th edition shotshell manual. Ballistic Products is not what it used to be for data. They really started to decline fast in the mid 2000's, I'm not really sure what changed or why. They used to put out the greatest manuals. Today they aren't even worth being toilet paper. The last one I bought was their Advantages manual which should have most of their data in it. I don't think I've ever found a single objectively good load from that manual, most are poor at best, some are unusable, a couple are dangerous.
If you can be more specific, what shotgun, what kind of performance you want, what kind of waterfowl, etc. I can give you data, and a list of things to buy.