I bought one of these Diana Bullseye ZR mounts for my HW97K and then gave up on it after a few tins of pellets because a significant amount of play had developed and I was getting a lot of point-of-aim shift. You'd get a group going-- then whammo, its like you started a whole new group at 1/2" in some other direction.
Tightening the ring-to-rail mini hex set screws did not solve this problem. The negative reviews on Pyramid pretty much cover the situation. The rails and the mount body clearly had a few thousandths of play. With the gun locked down in a vise you could see up to 1" of wiggle on target at 30 yards.
I sprung for a BKL one-piece and stuck the Diana ZR in the "good ideas that didn't pan out drawer" (way too much stuff in that drawer BTW).
But then I bought a true "scope killer" - the RWS 54 Air King in .22. I went with a droop compensated one-piece mount. But while printing some OK 50-yard groups at my club, more than one highly experienced shooter warned me that it was a virtual guarantee that my scope wasn't going to survive the beating. Two of these shooters had first hand experience in the matter. "Get a Diana Bullseye ZR", they urged.
I told the "my ZR has play" story and made my "I'll never buy one of those again" declaration. One match-competitive RWS 54 shooter nodded knowingly and then pointed out some added screws in his ZR mount that I hadn't noticed. He then shared his voodoo -- which I am about to share with you.
The trick involves some drilling and tap work to install your own grub set screws in the mount body. (I ain't no machinist, and in fact I screwed up a drill hole, and this still ended up working out).
I went with a 4 grub configuration using 4M x 0.7 set screws (4mm). With the mount fully DISASSEMBLED I tapped holes in each of the 4 corners of the mount body to allow the set screws to intercept the rails upon re-assembly.
Each time you set a grub you compress the mount and lightly tighten the screw until the mount rail is "locked". Then you begin to loosen the grub until the moment the mount releases. Do this on all four corners and use blue lock tight so that the grubs stay exactly in position. We are talking thousandths here, so its very important that the screws don't turn from their position even a degree or two.
Damn if it didn't work (at least in the first few hundred pellets). The mount absorbs recoil and the rails slide freely but WITHOUT THE PLAY thanks to the light pressure applied by these grub screws.
It is important that the grubs are brass or some other material that is SOFTER than the steel rails, otherwise you'll end up scoring the rails as they slide for hundreds or thousands of shots. (I've got some brass on order, it was hard to find).
Among the photos I attached is a 10-shot 50 yard group shooting 16gn JSBs out of the Air King with its improved ZR mount. This was not achievable before the fix. The other pics show one of the grubs (just above my finger with blue lock tight visible).
That ZR mount was not cheap and I am a bit dismayed that either A) the production run I got did not meet specs resulting in play over time, or B) this set screw solution is not part of the ZR design to start with.
For those of you experiencing play in your ZR mount, it is not all in your head, and yes, those few thousandths really matter, and no,the ZR afflicted with play will NOT settle in the same spot after each shot (wishful thinking).
Perhaps I should have just sent the ZR back where I got it (Airguns of Arizona), as I am certain they would have made good by sending out a new one. But I was convinced I would just end up with the same headache at some point. So nothing ventured nothing gained by taking a drill bit and tap to it. So far, so good.
Tightening the ring-to-rail mini hex set screws did not solve this problem. The negative reviews on Pyramid pretty much cover the situation. The rails and the mount body clearly had a few thousandths of play. With the gun locked down in a vise you could see up to 1" of wiggle on target at 30 yards.
I sprung for a BKL one-piece and stuck the Diana ZR in the "good ideas that didn't pan out drawer" (way too much stuff in that drawer BTW).
But then I bought a true "scope killer" - the RWS 54 Air King in .22. I went with a droop compensated one-piece mount. But while printing some OK 50-yard groups at my club, more than one highly experienced shooter warned me that it was a virtual guarantee that my scope wasn't going to survive the beating. Two of these shooters had first hand experience in the matter. "Get a Diana Bullseye ZR", they urged.
I told the "my ZR has play" story and made my "I'll never buy one of those again" declaration. One match-competitive RWS 54 shooter nodded knowingly and then pointed out some added screws in his ZR mount that I hadn't noticed. He then shared his voodoo -- which I am about to share with you.
The trick involves some drilling and tap work to install your own grub set screws in the mount body. (I ain't no machinist, and in fact I screwed up a drill hole, and this still ended up working out).
I went with a 4 grub configuration using 4M x 0.7 set screws (4mm). With the mount fully DISASSEMBLED I tapped holes in each of the 4 corners of the mount body to allow the set screws to intercept the rails upon re-assembly.
Each time you set a grub you compress the mount and lightly tighten the screw until the mount rail is "locked". Then you begin to loosen the grub until the moment the mount releases. Do this on all four corners and use blue lock tight so that the grubs stay exactly in position. We are talking thousandths here, so its very important that the screws don't turn from their position even a degree or two.
Damn if it didn't work (at least in the first few hundred pellets). The mount absorbs recoil and the rails slide freely but WITHOUT THE PLAY thanks to the light pressure applied by these grub screws.
It is important that the grubs are brass or some other material that is SOFTER than the steel rails, otherwise you'll end up scoring the rails as they slide for hundreds or thousands of shots. (I've got some brass on order, it was hard to find).
Among the photos I attached is a 10-shot 50 yard group shooting 16gn JSBs out of the Air King with its improved ZR mount. This was not achievable before the fix. The other pics show one of the grubs (just above my finger with blue lock tight visible).
That ZR mount was not cheap and I am a bit dismayed that either A) the production run I got did not meet specs resulting in play over time, or B) this set screw solution is not part of the ZR design to start with.
For those of you experiencing play in your ZR mount, it is not all in your head, and yes, those few thousandths really matter, and no,the ZR afflicted with play will NOT settle in the same spot after each shot (wishful thinking).
Perhaps I should have just sent the ZR back where I got it (Airguns of Arizona), as I am certain they would have made good by sending out a new one. But I was convinced I would just end up with the same headache at some point. So nothing ventured nothing gained by taking a drill bit and tap to it. So far, so good.
