I manufacture a large array of feedneck adapters that are intended to convert markers so they can use a latching feedneck that fits Empire's mounting specifications. Sometimes the feedneck adapters must be pressed-in, which usually works perfect, but sometimes a marker body doesn't have enough material for the existing feedneck to be removed and a new one installed. In cases like this, the feedneck can be milled down and converted to an Empire-spec mount. This milling process involves leaving the existing feedneck in position, but modifying it directly.

I've only had to perform this modification a small number of times. The marker body shown on this article is an X5 Vengeance Autococker from ANS, which has male STO feedneck threads (common for Autocockers) which are pressed into the body on top of a tall piece of material that sits about 3/8" above the marker body. So even if a press-fit Empire-spec adapter were available, the feedneck would still sit about 3/8" above the marker body. Directly modifying the feedneck is a better option for this body.

X5 feedneck before modification

I measured the marker body and realized I could mill off the threaded area to its base, which would leave about 0.200" of material above the marker body. The Empire-spec mounts require 0.180" of material, so this is just about perfect. To accomplish this, I mounted the marker body inside a typical milling vise between two pieces of wood which would provide a reasonably solid squeeze on the body without squishing it. Then I milled down the entire area:

X5 feedneck milled down

Once the new "top" surface was finished (above) there are two cuts remaining: the outside finish pass for the large mounting diameter, then a small "lip" undercut for the feedneck to latch.

X5 feedneck outside surface finished

X5 feedneck undercut

Done! The new mounting point is positioned fairly close to the upper bore, and is integrated right into the body since it used the existing feedneck. It turned out perfect, ready to hold a new feedneck.

X5 feedneck mod complete

While this mod is simple, it unfortunately requires use of a mill in order to accurately measure the proper diameters and depths. It could be done on a manual mill, but a CNC makes the job easier.