The fit of the two parts is why I am interested in any published standards for lunette and pintle dimensions.
I've got a copy of A-A-52550 which is the CID spec for the 18K, 40K and 100K pintle assembly hitches. Unfortunately, the inside diameter of the pintle is controlled by other specs, specifically international standardization agreement ASCC AIR STD 11/8, QSTAG 264, and STANAG 4101. This CID also states that these pintles as being interchangeable with MS51335F, MS51118F and MS51117E.
I have the MS51335F and it states the following: "Applicable provisions of ASCC Air STD 11/8, QSTAG-264, and STANAG 4101 are marked with an *. This dimension shall be of such size that it will accept a 3" x 1.66" lunette (see MS51336)."
I've also got MS51336 which shows the lunette hole being 3" +/- 1/32" FWIW.
The STANAG spec shows the lunette size but not the pintle dimension shown in -52550 and IHS standards and specs shows nothing for the AIR STD or QSTAG specs, so we're hosed there.
There are some trailer specs and drawings that may show the pintle sizes, post up your trailer type (m101, M-105, etc.) and I'll see what I can find through the Boring Library system.
Al