I found 5,56x45 cartridges from local shop that are claimed to be NATO surplus. Headstamp with NATO cross in a circle and SB (Empresa Nacional Santa Barbara de Industrias Militares SA, Toledo, Spain ?) supports that, but I can’t identify what NATO type it would be (e.g. M193, SS109…).
Bullet weight is 4g/62gr and it seem to have copper/brass coat on steel/iron (magnetic) jacket and lead core. Tip has (too small) structure I can’t identify to any NATO cartridge/bullet although it has NATO cross in a circle. To my knowledge, combination of the bullet structure and weight does not match. What military cartridge type it could be?