I really don't want to take anything away from a company producing specialty ammo, but you don't have to buy it. You can easily make your own with a Lee loader and Lee moulds.

I watched the armor piercing video - might have been better if not done in a gravel pit, but it was OK and showed the results they were after, but actually displayed nothing special.

The same results, only more demonstrative, happen with WW balls from a 12 bore - which can be over 500gr., not a mere light-weight, 7/8oz as in the video. Even a little 475gr. WW ball from the el-cheapo Lee mould will do it and do it well.

As for the multi-ball loads of different sized balls, those-too are well within the relm of any handloader. For a .410, merely size down some .440's, or use .395's as-cast. At 94gr. each, they're some 50% heavier than triple ought buck - each, which means greater penetration.

All of the smaller bore sizes are well represented by Lee at about $16.00 to $24.00 per mould size, SC or DC in smaller sizes from .562" and smaller.