...the lip where it is designed to hold the factory barrel. The exterior, where the larger bor eis located is real close to 7/16, but shy slightly. You will need to go through that as well.
Start with a bit the same size as the existing hole to true it to the inner smaller hole. Once you have done that, use a 7/16 drill bit to go through again. This way the Crosman barrel fits without having to use lube to slip it in.
A little tip that is worth doing, once you have gotten the 7/16 hole drilled to allow the barrel to slip on through: On the bottom of the slide/pump lever, towards the muzzle of the plastic, there are two small holes from the injection molding process. You can use those same two holes to drill into and then tap them. Put two set screws in the holes to assist in keeping the barrel from moving as well. You can counter drill two small holes in the barrel so the set screw recess into the barrel to create bite.
The fake ejection port (where the strap is located) needs to be wider to accomodate the larger diameter barrel as well. All pretty easy to do.
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