For those wanting to use someone's rifle scope and not change its eyepiece focus, you can put a corrective lens of the right diopter on it. Probably not more than a .25 or .33 diopter corrective lens of either + or - correction. Lenscrafters made a -.25 diopter one for me years ago that I put in place with a Butler Creek scope cap after removing its lid and hinge. It changed the magnification about 10% less but at least I could use that scope without moving its eyepiece.
You can also increase the power of a scope by putting in a + diopter lens on the eyepiece. The eyepiece has to be screwed in further and it reduces the eye relief. I changed a 16X scope to a 25X one that way; eye relief went from 3 inches down to 2 inches; just fine for a smallbore match rifle.
US Navy Distinguished Marksman Badge 153
Former USA Palma Team Member
NRA High Power Long Range High Master
NRA Smallbore Prone Master