Thread: 303 bullets tumbling

I've just bought a Lithgow 303 at a gun show and grabbed a bunch of that Greek 303 bunker ammo to test it out with.
I haven't put a scope on it yet so was trying to sight in the sights and was unable to hit the targets, after putting up a large board behind the targets, I could see they were getting close, but grouping was not tight and they look like they are going sideways.

I'm hoping its just this cheap ammo at fault, but I thought people found this stuff great.

Any ideas? The rifling in the barrel looked ok to me, that's one reason I bought it. The whole gun looks rather mint I thought.