Parker hale m85

[Gil Boyd]

They are about and often up for sale here in the UK.
I load my rifle round at a time, so don't use the mag for what it was intended, however, on occasions I have let other people fill and fire, they have had feeder issues caused by the lip of the short mag.
I tend to rest my springs when not in use and lightly oil them when ever I can, which seems to overcome that problem.
Are you using 7.62x51's?
Gil