British Pens, Major contractor for Browning AN-M2 (.303) gun Link Mark B1
Same general profile of US Link .30, but larger at neck (.303 bullet) and Smaller in Shoulder and Body ( .303 slimmer than .30 cal). Billions of Links made in WW II.
That said, the US .30 cal Link can be “tightened up” by extra crimping, to give a workable .303 Link.
These days, because of the Great quantities of Link expended in Aircraft (Total Loss) and small amounts of Military Surplus Belted ammo ( 1970s-80s) sold for General shooting, there is very little of this Unique Link left around (I have several thousand left over from that time…but I had/have a couple of Browning Mark I and I* Guns as well.).
For Brownings ( Aircraft and Ground) there have been US …30 cal, Portuguese/FN-made 7,9mm, British .303, 7,65mm (Argentine) & Venezuelan (FN-made) 7mm (x57) profile Links. All same general Prideaux Patent Profile, but slightly different Blank stamping dimensions due to calibre differences. NO “aircraft Brownings” (AFAIK) have been converted to 7,62 Nato, although the M1919A4 has been converted (USA, Israel, Maybe Morrocco), and special “7.62” Links have been made.