I think the use of “dummies” are very offen different from country to country. In Denmark we also have some special “dummies” to simulate faults by the gun.
No one from left has removed about 50 % of the rim and no. 2 has the head removed, both will give problems by extraction. No. 3 has some dents, which will secure that the cartridges will lock in the champer of the gun. All 3 “dummies” were used in training soldiers.
Does anybody know if any other country used “dummies” like that?