I owned a H5 scout manual
Superb rifle.
Only shot JSB 10.34 accurately, but extremely accurately.

I had 5 mags.
2 of those had issues where they'd drop the first shot low, so they got marked up and put aside.

I think the best advice is find a good mag, set the barrel clearance to that mag, and just use the one mag.

Mine would shoot true single hole groups at 35 yards. I've not owned many other rifles that would do the same.

Selling that H5 was one of my biggest regrets, but I had no other option at the time.