Thread: Headstamp on 303 reloads

My neighbour just bought a 303 as his first rifle and was trying to sight in at the weekend, along with his ever so know-it-all mate.
I popped up to see how it was going to find he had gone through a whole box of 180 Winchester and was still not able to hit a 6 inch gong at 100 yds. (it was actually only 84 yds when I ranged it )
His mate dug a few re-loads out of his pocket and told him to use them. The first two failed to fire, despite primer being well and truly pricked. The third shot went off.
It was only while he was getting sorted for the third shot that I picked up one of the mis fires, and noticed that the head stamp didn't mention 303 .
It simply had cac 7 stamp on it, as did the other reloads. I tried to suggest that it was possibly dodgy amo, but his mate insisted that he had used at least 30 of the same without issue.

My knowledge on this is next to nothing, but it didn't seem right to me. Was I right to be concerned ?