I used a pipe cutter (very carefully) to make a
shallow annular groove. It has the advantage of not raising a ridge alongside the groove as long as you keep the cut depth shallow enough. It does tend to ruin the pipe cutter BTW, buy a a cheap one & think of it as disposable.
__________________
Allan Quatermain: “Automatic rifles. Who in God's name has automatic rifles”?
Elderly Hunter: “That's dashed unsporting. Probably Belgium.”