The US Navy contemplated two calibres of automatic anti-aircraft cannon: 35mm and 50mm.

美國海軍考慮了兩種不同的高炮口徑:35毫米和50毫米。

The results of the studies conducted during 1949 and 1950 formed the basis for a mandate which Oerlikon received from the US Navy to develop naval guns in the calibres 35mm and 50mm.? As a result, the 35mm twin naval turret was constructed and delivered to the US Navy.? The ammunition and cannon then became the basis for the terrestrial Oerlikon twin AA gun with Contraves fire control system.

在1949年和1950年期間進行的研究結(jié)果形成了厄利孔從美國海軍獲得的開發(fā)35毫米和50毫米口徑艦炮的授權(quán)的基礎(chǔ)。作為結(jié)果，35毫米雙聯(lián)炮塔被建造并交付給美國海軍。彈藥和火炮炮隨后成為厄利孔的地面雙防空炮與康特拉夫火控系統(tǒng)的基礎(chǔ)。

The 50mm project, which was designated 501 MK (50mm type 1 machine cannon), does not appear to have gone beyond internal ballistics testing in a pressure barrel."

而50mm項目被命名為501 MK (意為50mm 1型機炮)，似乎沒有通過在壓力槍管（一種測驗膛壓的彈道槍管）中進行內(nèi)部彈道測試?！?/p>

Source: An article by Bob Gerber in April 2011 issue of the ECRA Bulletin (No.552)

來源:Bob Gerber在2011年4月ECRA公報(第552期)上的一篇文章

Bob goes on to provide more detailed information including a measured drawing of the 50 x 355 501 MK (which is not the same as any of the 50mm examples in the “forest” study). The relevant page in the ECRA Bulletin is shown below:

Bob繼續(xù)提供了更詳細的信息，包括50 x 355 501 MK的測量圖紙(這與“forest”項目中的任何50mm示例都不一樣)。ECRA公告的相關(guān)頁面如下:

另外的照片顯示，除了35x228和40x364R Bofors外，僅有的兩個仍然存在的50x355彈藥筒(在Schweizerischen Milit?rmuseum fullreuenthal展出)：

不同尺寸的炮彈大小對比：

(左到右)

47-60mm EXPERIMENTAL CARTRIDGES FOR AUTOMATIC WEAPONS

47x326R Vickers Class P (ac/AT)

47x428R Vickers 3? pr (naval AA, repA)

50x330 (Supershot, necked-up 35x228, German 1980s, RepP),

50x355 501 MK (Oerlikon for USN, late 1950s, repA)

55x450B Ger?t 58/MK 114 (German AA/ac, late-WW2, repA)

57x515R 6pr 6cwt (British AA, 1940s)

60x408R (IMI/OTO 1980s AFV)