I am looking for the same. I am willing to spend more, but much more expensive scopes aren't well suited for the rifle because they will be excessively large or heavy.
I have a VX3 1.5-5x20 on there now with the CZ rings which are 0.550" over base and 1" diameter. The bolt handle clears by about 0.2" so I believe I can lower the base or increase the ocular diameter by that much. The high rings do not work well without a raised comb. With the Boyds' At-One stock, I can raise the comb, but I greatly prefer the original CZ stock and the original stock is more in keeping with the rifle's classic style and light weight. Using lower rings is possible, but the well-known issue is the high bolt-handle angle that is a characteristic of the Mauser-style action with its 90-degree bolt-throw. The bolt handle will interfere with larger diameter oculars if the scope is much lower. With the Leupold's 1.6" diameter ocular, I have about 0.2" clearance (without the Butler Creek slip-on lens covers). Note that newer Leupolds have internally threaded lens housings to accommodate flush lens caps. So if I lower the ring centers by 0.15" using Talley 0.400" rings, a 1.6" ocular will just clear by 0.05". Note that Warne 0.425" rings will give you 0.025" more. Going lower to Talley's 0.300" rings would be nice, but I'm afraid the selection of scopes with ocular diameters below 1.5" is too restrictive. Perhaps the bolt handle could be reshaped, but I'm not doing that.
So I've determined with the lowest practical 0.400" rings, the ocular diameter should be 1.6" and if it's more than 1.65" it will probably require 0.425" or 0.500" rings. With the lower rings, the objective housing diameter should be 2" or less. This rules out most of the 50mm and 56mm objectives, but those scopes are probably not a good size, weight, and magnification fit for this rifle anyway. It would be anti-thematic to use high rings and mount such a large telescope on this little rifle for my intended use which is hunting where I value light weight and lower magnifications.
I have been able to shoot this rifle with 1.5 to 5X (note the Leupold is really a maximum of 4.5X) and I find it comfortable shooting out to 400 yards. This is beyond the range I would hunt with it so I feel 4X is acceptable and anything more than 6 or 7X is not useful for my purpose. I like low magnification and wide fields of view, but I don't hunt in dense forest these days. It's usually wide-open mountains with few trees. Because of the distances, I favor a larger objective, and easier-to-find exit pupil at 4X than I do the ability to go down to 2X or less. Because of this, I'm not really looking at 20mm or 24mm objectives, but otherwise I think they are a great fit for this rifle (and I am using one now).
My kids use this rifle and with the short length of pull, a long eyepiece and long eye relief can be a problem. At the lower magnifications where the eye relief is longer, they get eyeshadowing because they can't pull their head back far enough and the scope won't go any farther forward in the rings. It's actually the turret housing that limits its forward movement. Long eyepieces (which includes all the VX5 and VX6) and scopes with longer eye relief at low power could make it difficult unless there's plenty of length in the stock. The factory stock is somewhat short at 13.5" LOP. But the real problem is when it's shortened to 12.5" for one of my kids.
So let's consider some scopes keeping in mind a preference for low-mount, emphasis on magnification between 3X and 7X, objective diameter less than 50mm, and with those three factors, probably a 1" tube diameter, weight on the low-end and a reasonably slim eyepiece. Otherwise, let's look at some top-quality scopes.
Most of the Schmidt & Benders are large and heavy. Of the few with smaller objectives, the 2.5-10x40 Summit and 6x42 Klassik stand out. The Summit has a low 1" tube but the eyepiece is 1.69". More concerning is the 21 oz. weight. The height and weight result in a less than ideal fit. The Klassik is only a bit lighter and still over a pound. It's available in a 1" tube version and it's eyepiece is 1.61". The eyepiece is long, but I won't concern anyone with this since it is probably not a concern for most with a normal length of pull. Among the Schmidt & Benders, The Klassik is probably the best fit.
Like the high-end Schmidt & Benders, we will skip the Zeiss Victory line because they are tall with large eyepieces (1.8" diameters) that would require a higher comb. The Zeiss Conquest line's eyepieces are not much smaller and still quite large at over 1.7". A few to consider with suitable magnification levels and objective diameters would be the Conquest V4 3-12x44. At 18.8 oz, it's heavy. With the large eyepiece and 30mm tube, it would mount high.
I was not able to find the eyepiece dimensions for Leica rifle scopes but photos suggest the eyepieces on the ER and Visus 42mm scopes are about 45mm. Again, these are tall and heavy scopes better suited to a larger rifle with a higher comb.
Swarovski offers Z3 scopes that are more suitable to the 527 and my use than the S&B, Zeiss, and Leica. The Z3 eyepieces are 1.57", but the Z5 eyepieces, as well as Swarovski's other scopes, are 1.69" or larger. Among the Z3's there are 3-9x36 and 3-10x42 models. 10x is not useful for me. Would the 42mm objective be brighter? At 7X it would have a 6mm exit pupil instead of 5mm. That would be brighter for the young ones, but for me probably only a little easier to find. Below 7X, the exit pupil would probably be large enough on either. The 36mm scope is about half an inch shorter in length and about half an ounce lighter besides being a little more compact in diameter.
Nightforce is mostly larger scopes, but they have two smaller ones that will fit. The NXS 2.5-10x42mm and the SHV 3-10x42mm. Both of these have 40mm eyepieces. They are both quite heavy at over 20 oz.
Leupold probably has the greatest selection of scopes that will fit this little rifle well. The VX6 HD and VX5 HD's all have large 1.8" eyepieces and 30mm tubes that prevent a low mount with the 527's high bolt handle. In other series, the VX-3i 2.5-8x36mm and VX-R 2-7x33mm are a good fit with low weight. The 36mm scope is actually lighter because it lacks the illuminated dot reticle. Other Leupolds that are a great fit are the FXII 4x33mm and FX3 6x42mm. These fixed-power scopes are simple, light, and have a short eyepiece. The 4x33 is especially accommodating for the 527's fixed mounts when using a short length of pull. It also offers a generous 8mm exit pupil and what is probably the most useful magnification level for deer hunting with a rifle like this. I am not familiar with the quality of the optics on a FXII or FX3. The fixed-power alternative is the Schmidt & Bender Klassik.
So the short list is:
Schmidt & Bender 6x42mm Klassik
Swarovski Z3 3-9x36mm
Swarovski Z3 3-10x42mm
Nightforce NXS 2.5-10x42mm
Nightforce SHV 3-10x42mm
Leupold VX-3i 2.5-8x36mm
Leupold VX-R 2-7x33mm
Leupold FXII 4x33mm
Leupold FX3 6x42mm
The SB and NF scopes might spoil the rifle's weight. I weighed it at 7.3 pounds, and without the Leupold it would be 6.7 pounds. I probably could have narrowed it to Swarovski and Leupold at the outset with a weight criteria that would exclude SB, Zeiss, Leica, and Nightforce, but by including those scopes in my consideration I learned that besides being heavy, most of them would be too high as well.
