I'd probably not install a diopter sight on a 300 Mag of any flavor. But for those who wish it, the following: The Lyman 48 seems generally the most popular of the breed. From 1917, three models. First 150 scale, second 125 scale and last... depending on sub model, but generally 50. 'Range diminished reflecting the fact of 'reaching out', typically with scopes! I have a few Model 70s with Lymans (including the Model 58, a $$ lesser model.
Ironically, 'arriving' installed on my pre '64 .338 Mag! Moving to a particular point concerning these fine Lyman 48 sights. The 3rd edition - limited range, but a "no inletting feature" on many rifles. Meaning no horrible stock carving to install. My .338, such style and 'achieving' no-inletting which is also subject to stock not being too thick in the sight installation area. I've also heard of folks shimming this Third Model to avoid slight inletting which, is essentially the same as 'slight pregnancy', in collector terms!
Some pix of my Win 70 'pre', .338 Win Mag, Super Grade w/such sight below.
Best!
John
