I have very little historical information on the 3.5 power PU telescopic sight. They were used primarily on the Russian Mosin-Nagant 91/30 sniper rifle system. The PU was also used on the Hungarian 91/30 sniper rifle as well as just about every other 91/30-based sniper rifle utilized by nations employing Soviet equipment. One of the more interesting uses of this scope was on the Finnish M39, a much-improved variant of the original Mosin-Nagant design and considered by many to be arguably the best bolt-action service rifle ever made. This particular usage is interesting in that these telescopic sights were typically removed from captured Russian 91/30's when the parent rifles became less than reliable or their accuracy began to decay. It is somewhat historically satisfying to know that the Finns were able to use the invading Russian's own specialized equipment against them.
First introduced in a slightly different model for the M1938 and then M1940 Tokarev (SVT) rifles, the PU in its final form, as found on the M91/30, measures 6-5/8th inches long and has a 30mm tube. It had an eye relief of approximately 70mm and the field of view is 4 degrees, 30 minutes. The PU telescopic sight, along with the longer 4 power PE, was the principal optical device used throughout WWII by Soviet forces. A simple design, it lasted in front line use right through the 1960's and can still be found in use in several third world nations. The recent influx of Soviet paraphernalia has brought many of these sights into the world market. These scopes are typically in excellent condition and make a nice conversation piece for any collection.
While simple, the PU seems to be quite well made and robust. There is no means for focusing the sight so corrected vision is a must. The low magnification allows some leeway, but if you were not blessed with perfect vision, you would not have been issued this sight as a Soviet sniper. The reticle is typically European; a three-post system consisting of a sharply pointed vertical post and equally thick square side posts that end just short of the vertical post. The gap between the horizontal posts can be used for range estimation and leads. The PU has a BDC style elevation turret calibrated to the 7.62x54R cartridge utilizing the .310 caliber bullet. The elevation turret is marked from 0 to an optimistic 1300 meters. There is no clicker plate and the turret may be turned smoothly between markings. One has to pay attention when dialing in an elevation change, as there is no positive feedback. Adjustment is strictly visual and in low light, a problem. Like the No. 32 Mk1, the BDC is rather gross in adjustment but in this case, the PU has a little "guestimation" room as you can infinitely adjust the turret between ranges. Of course this is anything but precise. Again, I believe the sniper would resort to holds to correct for changes due to weather. The lateral adjustment (windage) turret is similar to the BDC. There are no positive clicks and one must rely solely on vision to set the drum. The turret is marked from 0 to 10 in either direction. I can only assume this represents minutes of angle, but until I can shoot this scope, I have little to go by but faith.
As an interesting aside, the Germans were so impressed with the PU that they based their ill-fated Gw ZF4 telescopic sight on it. The idea of a mass-produced sniper scope must have been overwhelming to the hard-pressed German military. They had to rely on what essentially amounted to high quality sporting scopes, which where both expensive and hard to come by. The lure of a small and easily produced telescopic sight soon had them creating a copy of the PU with the intent of massive distribution. I'll cover this in the following text.
The glass in the PU is fairly clear but appears to be uncoated. Tested against the Zeiss Test Pattern, I found an interesting anomaly that I am unsure how to classify. The scope was capable of resolving down to the number 4 block. At times I felt I could resolve to the number 5 block, but not with any consistency. The odd anomaly I spoke of still has me stumped. When viewing the center of the field of view, the Zeiss pattern appears sufficiently crisp, but it actually sharpens as I move toward the edge of the image area! This is exactly opposite of what you would expect. The closer I looked toward the edge, the better the resolution. This held up right up to the edge, where the image darkened slightly and lost a little focus. I have never experienced this before. Typically the sharpest image is at the center of the scope and one usually loses that clarity out near the edge of the glass. This anomaly could be the result of not being able to focus the sight to the individual's eye. In the field, I could not notice any difference in the image, but under close examination with the Test Pattern, it was easily discerned. On the plus side, I could discern no noticeable distortion. Straight lines remained straight right to the edge.
Zeroing the PU scope is quite simple. Verify zero on paper. Loosen the two large screws found on the top of the turret and gently slide the marked outer drum to the correct range indicator. Gently tighten the screws again and re-verify the zero. This is a quantum leap ahead of the No. 32 Mk1. Bore sighting the PU is relatively easy. The turrets provide enough resistance to stay at the desired setting, yet are easily displaced when needed. While I would much prefer a positive clicker, the smooth action of the PU turret works sufficiently for its intended purpose.
I would have to rate the PU quite acceptable for its purpose. While simple, it provided a mass-produced means of arming the Soviets and her satellites with an efficient and reliable telescopic sight. By no means a precision instrument by today's standards, it was sufficient to net kills in excess of 800 yards in capable hands.