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M21 Scope

Mister Ridge

Sergeant
Full Member
Minuteman
  • Aug 15, 2011
    1,540
    1,825
    Maryland
    Before we start, I would like to say that this has absolutely nothing to do with US Army M21 sniper rifle or its optics.

    Awhile back, I posted about a scope I found on an auction site. That scope was listed as an M45 scope and it was fit into Unertl Target scope rings. I thought it was a neat idea but questioned how well it could work. There was nothing keeping the scope lined up in the rings and I was hesitant to purchase this kind of scope without looking through it first. The reason for this is because the M45 scope and scopes like it are not rifle scopes at all. They are in fact gun sights off artillery pieces. By some coincidence, my local gun shop had one. It was the cause of my concerns about buying this type of scope without looking through it first. The scope is actually proportioned backwards to what a rifle scope is. In use on an artillery piece, you look through the small end. As luck would have it, this one can be looked through both ways. Unfortunately, I suspect that is because it has no magnification. The issue of the scope solved, I figured out a way to securely mount it in the rings to prevent rotation. Being that the scope has no internal adjustment, it needs externally adjustable rings. The Unertl and other target scopes float in the rings and have ribs in the body to prevent rotation. The artillery scope did not. To get around this, I used a set of rings off a 2.5x Texan scope I bought off ebay. The rings I used appear to be the same rings used on the Weaver V8 scope and may have been pulled off one. Eventually, I would like to get another set so that these rings can go back on my Texan scope. Now, with a set of rings, a suitable scope, and a set of ring reducers from Brownell's, I put together the scope pictured below and theoretically adapted an artillery scope into a rifle scope. Sadly, I don't yet have the rifle I would like to put this on. Currently, the scope is mounted on a 10/22 and I will begin preliminary testing later this week. If all goes well, then one day it will be mounted onto a Creedmoor Sports 1903A4. Even without historical accuracy, I feel that this is an awesome little toy to have and a great conversation piece. Take a look! I will post more pictures soon. It has a really neat reticle.

     
    A few more pics. First one is of the markings.

    They read as follows:
    TELESCOPE M21\NO. 789
    M.H.R. CO. 1941 -----D.A.


    Next are a few pics od the mounts. You can just sorta see the ring reducers. The turrets are covered by the round caps.


    Finally, we have the reticle itself. Based on the markings at the bottom, this scope came off a 75mm piece. What's interesting is that, with complexity of the reticle, it was entirely possible this could have been done in WW2. With the windage adjustment in the base and some shims to provide for elevation, this scope could actually be mounted in a set of Redfield rings, zeroed, and been used just like the Japanese Type 97 sniper rifle. The scope on that rifle had no adjustments either, being zeroed by the arsenal and aimed by holding off as needed. The same thing could be done to 1903A4 using this scope and the issue mounts with a different set of rings. The reticle provides for windage and elevation hold-off, along with ranging. It would have taken practice but it could have worked quite well. Might even have been a little more reliable than a Weaver 330. Food for thought.
     
    Actually, that optical sight is part of the main gun (M2 75mm) sighting system for an M3 Medium tank.

    from FM 23-95

    c. The reticle of the M21 telescope (fig. 16) contains a vertical crosshair and several horizontal crosshairs. The horizontal crosshairs are based on elevations for ranges from 0 to 3,000 yards, spaced each 500 yards and numbered every 1,000
    yards. Five and ten mil lead ticks are placed on either side of the vertical hair on the 500-yard range line. This reticle is designed for ammunition which has a 1,850 foot-second muzzle velocity.

    You might be a little hard pressed to make it work beyond getting one cross hair on target at a known range.

    I have a May of '42 copy in my reference library... for no other reason than I got hooked on the M3 tank as a little kid after watching Humphrey Bogart in Sahara.
     
    Actually, that optical sight is part of the main gun (M2 75mm) sighting system for an M3 Medium tank.

    from FM 23-95

    c. The reticle of the M21 telescope (fig. 16) contains a vertical crosshair and several horizontal crosshairs. The horizontal crosshairs are based on elevations for ranges from 0 to 3,000 yards, spaced each 500 yards and numbered every 1,000
    yards. Five and ten mil lead ticks are placed on either side of the vertical hair on the 500-yard range line. This reticle is designed for ammunition which has a 1,850 foot-second muzzle velocity.

    You might be a little hard pressed to make it work beyond getting one cross hair on target at a known range.

    I have a May of '42 copy in my reference library... for no other reason than I got hooked on the M3 tank as a little kid after watching Humphrey Bogart in Sahara.

    Neat. This is will be really fun to mess around with. Currently, I have next to nothing in it so I feel I'm still ahead. Also, what I said about practice might definitely be true. Fire a lot of rounds and see what lines up. I'm guessing you're right, not much will. I will continue to search though. I have seen another scope that had a BDC reticle like this, one with a standard crosshair, and, supposedly, some actually had magnification. There is even one of these listed on gunbroker that someone made into an regular rifle scope with internal adjustment and an objective bell that appears to be a scope booster. Unfortunately, the seller thinks it is a sniper scope and wants crazy money for it. Adapting these into rifle scopes will provide a lot of entertainment.
     
    They were originally mounted in an M1 periscope that looked over the hull sponson.

    Good luck with your project... always had an affinity for externally adjustable scopes... like the B&L Balvar.