The very first .303 ammo that I ever shot was POF, back in 1985. I bought it along with my No.4 Mk. I at Woolworth's.
Even nearly 30 years ago that stuff was crap. Numerous hang fires and the ammo that did go off must not have been developing full velocity, because the recoil was noticeably less than the good milsurp .303 available in the 80s (e.g., Winchester, MEN, and HXP).
Spend a bit more and buy some Prvi Partisan, Sellier & Bellot, Herter's (made by S&B), or some HXP from CTD. You will be much happier with the ammo, and it has nice, reloadable brass.
I just got a case of the HXP. It's all vintage 1976, clean, and it came in clips. A case of 450 rounds came with 90 clips, which are worth $1 to $1.50 each.