I think they just add to collector value. They are a pain to use. I have a 53 and I used the inserts only one time. I also have the extra cylinder and I tried that a few times and seen no advantage in that over my K-22's. With both of these (the inserts and the extra cylinder) and using match ammo the accuracy was not very good.
This just might be my revolver with such poor results but I don't think so. When using 22 jet ammo it is spot on.
I have another model 53 that is NIB and I was tempted to shoot that but I change my mind, I'm just going to sell it now as I don't need two shooters.
A Model 53 with inserts or extra cylinder would be just as accurate as a Model 17, but it might depend on the revolver. I never noticed any difference other than the inserts are a pain to use. They would add to the value.
I have never owned or shot one, but it is my understanding that the 53 was bored for the 22 magnum, which may be part of why it had less than desirable accuracy with 22 LR.
A set of 6 sold on ebay not long ago for $175.00. People that have nice Model 53's with the box but missing the inserts are willing to pay to complete the package.
I am very lucky, that in my old age, I have so many .22lr revolvers, I am torn as to which ones to shoot. To go through the motions, of placing .22s in inserts and then prying them out and reinserting the inserts, seems ludicrous. I have tried it, and the use of .22lr in the Model 53 is fine. I have not compared accuracy, but it is fine in my 8.75" M53, and in the 4" version. I see no difference in accuracy using the extra cylinder in the 4". My 6" M53 is unfired….NIB. I handload the Jet and accuracy is fabulous…so is the display of fire…below is my 8.75" gun with H110 under the 40gr. bullet. When I spray the cylinder with lighter fluid or degreaser, the brass simply falls out of the chambers. This is way more fun than .22lr….light up the sky and generate sound that will embarrass a .44 Magnum….for.22lr I use the K22.