Based on the replies here & some speculation elswhere I got interested & did a quick web search. Interesting.
Britain supported Greece till the Greek civil war, then dropped them like a hot potato so the U.S stepped in to the gap.
(Greek Powder & Cartridge Company,
1, Ilioupoleos Ave.
(PYRKAL) S.A. is the oldest Greek Defense Industry, as it was founded in 1874. Today, PYRKAL:
Manufactures a wide range of NATO type Ammunition, from 5.56mm up to 155mm, Rockets and Fuses.
Is the Greek MoD's exclusive supplier of ammunition.
Exports its products to all five Continents.
Is a State owned company, having three plants, and maintains a staff of 1300.
Holds an ISSO 9002 Certification.)
Made nitro-cellulose loaded .303 cartridges in. Ball, L1A1 to British Government contract (1982-85)
& Ball (1969)
303 British ammo with a headstamp "HXP 75". when disassembled it contains 41 grains of ball powder, a 174 grain FMJ bullet, and is boxer primed.
In the 1960s, the factory, under NATO/US agreements, became part of the US Offshore Procurement Program; as a result, machinery and technology from Olin Industries (Winchester Western) was set up in Piraeus to make US cal. ammo at US Specifications, with Olin Ball Powder; as the Greek Army was then currently also using .303 British, they also made this ammo to the same technical specs.
As a result, any HXP marked ammo is of Winchester-Western quality (some say better), is Boxer primed, Noncorrosive, and with Ball Powder loading.
I've seen it claimed that HXP ammo was made on equipment from Britain, but there’s no similarity between the HXP and British MilSurp .303 that I can see.
Britain cut off foreign aid to Greece shortly after WW2 and the U S took up the slack in rebuilding Greece's arms industry. The Germans had stolen or destroyed all cartridge manufacturing machinery during the war."
Allan Quatermain: “Automatic rifles. Who in God's name has automatic rifles”?
Elderly Hunter: “That's dashed unsporting. Probably Belgium.”