So... was looking for an extra magazine for a Heym SR21 in .308. Discovered that Reeves stock them. On phoning ws overjoyed to discover that they stock a 5 round version.
At a not inconsiderable price, I bought one.
Magazine arrived today. Didn't look quite right, but tried it anyway (with no rounds). Mag is now firmly and irremovably stuck on the rifle. Absolutely cannot get it off by any of the normal ways.
All suggestions very gratefully received. Have to have this working by Friday ...