I doubt you will find much commercially available pure lead (99.9%) ammo, but will find soft lead. Casting pure lead consistently is difficult. FWIW I use about 2% tin. Even NSA uses 1% tin for swaged ammo with his insanely accurate presses, but still giving them a BHN of only 6. Pure lead (99.9%) is closer to 5. Some manufacturers use antimony and not tin, some maybe even both or even bismuth or some cheap chinesium. There is also the cnc’d slugs to consider. Not sure how that process would be affected by hardness, but even still, pure lead is generally considered too soft.
The anti-lead movement is strong in the EU. There is a bill proposed to ban it. Definitely another topic/thread to consider as the pellet and slug market demands would drastically change. Maybe the guys here from across the pond would enlighten us to the lead ban push.