Congrats on a tough job well done!
I've done similar to cone the inside of a flintlock flash hole or vent.
You may want to invest in an Optivisor as it gives you a loop for both eyes and is hands free without squinting to hold it in place like a loop requires!
OptiVISOR is a precision binocular headband magnifier which permits unrestricted user efficiency while reducing eye strain—leaves both hands free and allows three dimensional vision. Used by anyo...
There are many different sources for these, like most of the standard machinist supply outlets, or even Amazon and the like. There are also quite a few knock-off copycats, but I do like the original and use it all the time!