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A detailed look into how effective are ZR Mounts in protecting a scope in a spring-piston rifle.

3/14/2016

17 Comments

 
There have been doubts expressed about how effective the ZR Mounts are.
Some people have had broken scopes using the 2nd generation, some people have had scope slippage using the 1st generation of these mounts. So, let's take a look at them.

The 1st generation mounts suffered from a lack of absolute repeatabilty, which we corrected with our "Accurized" version.
The 2nd generation increased the diameter of the pins (from around 0.237" to 0.257") where the top section of the mount slides on as a means to overcome the lack of "register", and added a very viscous lubricant in order to provide some "dampening". Sadly, these improvements have proven fatal flaws.
The mounts can become so hard, that they do not eliminate ANY recoil, acting more like solid mounts than like floating mounts.

And this is the operative word: Float.

If you look at our High Speed Analysis of How ZR Mounts Work, you can see that what in effect happens is that the initial REARWARD recoil originated by the spring pushing the piston forward separates the floating section from the fixed section of the mount. This separation enables the piston to end its race towards the end of the compression chamber and the pellet to exit BEFORE the scope is affected. In other words, by the time the FORWARD recoil that kills scopes begins, the scope is not in a rigid relation to the bottom section of the mount. Therefore, the lower section of the mount CANNOT transmit the FORWARD recoil generated by the piston's race coming to an end. And so, the scope is saved from the brutal forward recoil.

Let's take a second first to think about what a recoil is.
In essence it is a force, but forces by themselves seldom break things. Even a china cup can bear enormous weights (forces) as long as the stress comes to the cup in a slow and constant manner.
What breaks things, in reality is when one section of that thing undergoes one acceleration while another section undergoes a different acceleration.
That is why destructive forces are measured in "g"s.
Of course the quantity that relates forces and accelerations is the mass (usually constant), so heavier objects suffer more from the same "g"s than a lighter object.

Sometimes people tell me that their rifles (specially the NP's) do NOT have a forwards acceleration. And some videos tend to show that NP's recoil BACK but suddenly stand still. There seems to be no apparent movement FORWARD.
What we tend to forget is that once an object starts moving, according to the Newtonian laws prevalent in OUR world, that object should keep on moving in the same direction and at the same speed that it was.
IF that object suddenly stops, it can only stop because a force, a "g times X" has acted on the object.

So, those NP's that SEEM to have no forward recoil because they do not feel to jump forward, may have a quite appreciable forward recoil; at least enough to stop the rifle, scope, and shooter's arms in its tracks once they had started to move to the rear.

But coming back to the ZR mounts our problem is HOW to look into how effectively the mounts isolate the scope from the rifle's recoil.
Someone suggested getting some accelerometers and instrumenting a scope. Sadly that is an economical hurdle we cannot overcome, BUT in the discussions that ensued, my Brazilian friend said something, ALMOST, tongue in cheek that clicked in my head; he said "if the recoil felt by the scope was Zero, then the scope could be simply lying on the mount and it should not move".

Hmmm, interesting point of view. Of course, even though the mounts are called ZR (zero recoil), it does not mean ABSOLUTE ZERO. The rifle moves, therefore the scope needs to move a little. We cannot simply put a scope in the bottom rings and expect it not to move. NOTHING is absolute.

BUT, some tests could be performed by starting at a VERY LOW torque of the rings' screws and increasing the torque till the scope did not move.

And that was the start of it! LOL!
I went and bought a FAT Wrench (FAT stands, supposedly, for Firearms Accurizing Torque). Basically it is a screwdriver shaped torque meter that accepts hex bits like we use in all the interchangeable bit drivers. What drew me to that, was it was the only fairly economical device that offered a calibration certificate.

Since I am working on creating a "Universal Rifle" that will do everything a reasonable airgun can do, I had ahead of me a torture test of some components inside the gun ("torture test" for CCA means 300 shots fired over the course of a morning, or afternoon, about 4 hours). We have found that components that survive this test usually survive well into years of common usage by FT shooters and that means decades of usage by hobby airgunners. So, it is our standard test of "endurance".

And I thought I would use the opportunity to test the idea: Start with the LOWEST setting on a torque wrench (in this case, the 10 in-lbs. setting has been calibrated by the manufacturer to be in reality 10.4 in-lbs), and shoot a lot with the  ZR mounts in a D54 and see if the scope crept in either direction. IF the scope crept I was prepared to go to 12½ in-lbs and see if it crept; if it crept, then I would go to 15 in-lbs. and see what happened there. Since 15 in-lbs is what "economy" scope makers think is the max they want their scopes torqued to, I would stop there for public consumption, but I would test at 20, 25, 30 and 35 in-lbs, which is the value that good scopes can take (on metric mounts with 3 mm's screws).

So I gathered all the necessary equipment:
Picture
​A close up of the rings and the scope:
Picture
The scope in question is a Sightron Benchrest 36X42 scope it is a 1" scope and in no way is it too light, nor too strong. I would say it is the most "garden variety" of the scopes in the Sightron line.

I degreased ALL mating surfaces with Lacquer Thinner:
Picture
​Do note how much "GUNK" came out with the degreasing. All this gunk can and will aid the scope in slipping the rings. Once the scope and the rings are clean DO NOT TOUCH THEM!

DISCLAIMER.-  Newer scopes have finishes that are not as resistant, so do NOT use lacquer thinner, but use rubbing alcohol to degrease instead.

Set my FAT wrench to the 10 in-lbs value planned:
Picture
And set the BASE screws to that torque:
Picture
​To make it easy to detect if the BASE had slipped I aligned the front of the base to the end of the rail:
Picture
And then using just TWO fingers, I started tightening the ring screws in a zig-zag pattern. It is IMPORTANT to NEVER tighten a screw more than 1/16th of a turn. Then move over and to the next screw, then over and to the next. Viewed from above it is a zig-zag that goes across the scope tube 7 times. ​
Picture
If you tighten one screw more than the counterpart of the opposite side, the scope may twist, and when it twists, it locks the slide. I have also found scopes that are NOT STRAIGHT, especially those that are made in 3 parts (foretube, afttube and saddle). 

IF a freely sliding ZR Mount locks, SOMETHING IS WRONG. Back off and analyze calmly what may be wrong. The Gen 1 ZR mounts slide freely, the Gen 2 need complete disassembly, then cleaning with Lacquer Thinner, and then you're back to a "functioning" ZR mount.

Anyway, continuing:
After ALL the screws have been snugged down EVENLY, then you start torqueing the screws into place:
​
Picture
Again, FOLLOW the Zig-Zag pattern!

And when the wrench "cracks", go back two or three times around all the 8 screws to make sure that you have not missed or stressed any screw above any other.

After I finished torqueing all the screws to the LOWEST setting possible, I made two "witness marks" in the scope with white grease china marker:
​
Picture
And then I proceeded to shoot.

After the first 10 shots, nothing had moved.

After the first 50 shots, nothing had moved.

I stopped worrying and proceeded with the 300 shots test, this is the result:
Picture
As you can see, NOTHING MOVED.

We can, therefore, safely conclude that ZR mounts, when properly setup, DO work.

I cannot stress enough that in airgunning what seems simple is, usually, an illusion.

The most basic things like tightening a screw can have repercussions in how the whole system behaves.

That is why there are a LOT of "EXPERTS" out there, but very few Pros.

Anyway, I hope this helps in making a good idea more functional to the majority of shooters.

Keep well and shoot straight!







Héctor Medina
17 Comments
Alejandro O Martinez
3/15/2016 00:25:22

Very interesting experiment. Moreover, I didn't know there were already two generations of the ZR Mount on the market. How are the early mounts distinguished for the latest versions? And, is there anyway a buyer can know if he/she is buying the latest version?

Reply
HECTOR J MEDINA
3/20/2016 19:15:02

Alejandro, as you can read in the entry:

"The 2nd generation increased the diameter of the pins (from around 0.237" to 0.257") "

So, that is the way to know what you have in your hands.

HTH




Héctor

Reply
RidgeRunner
3/19/2016 07:39:06

Hector,

I have been considering a ZR mount, but you have convinced me that I would not want such. If the first generation lacks repeatability and the second generation has a tendency to stop functioning, I think Diana needs to cease production until they can get it right.

The concept is great, but obviously not ready to go to market. The marketeers need to slow down and let the engineers get it right. Once it has repeatability AND functionality, I would not mind having a couple myself.

Reply
HECTOR J MEDINA
3/20/2016 19:16:54

RR:

Of course the decision to wait it out is yours.

In the meantime, dozens of others are simply getting a mount that has been "gone over".

To each his own.

Keep well and shoot straight!




Hector

Reply
Alejandro O Martinez
8/23/2016 23:36:41

Héctor, you once related that when installed on a full-power Model 54, under recoil the entire rail-travel of the ZR Mount is traversed. Resulting in the scope coming to an abrupt stop at the end of ZR Mount rail-travel. As such, when used on an Air King, the effectiveness of the ZR Mount is compromised. This being the case, would a Mod. 56TH with the additional mass of the muzzle weight, would the added weight of the muzzle brake help or hinder the effectiveness of the ZR Mount?

Reply
Hector Medina
8/26/2016 13:19:13

Alejandro;

I am in California, travelling, but I have a minute now.
There are several ways the ZR mounts can be used even in FP D54's and 56's.
The most reliable one would be to change the spring in the mounts for a slightly stiffer one and record that the slide does not reach the end of the travel with each shot.
You can do that with a 56 and see. Just use lamp black at the rear of the slide, or ink. If it stains the fixed part, it is not enough weight to make it work. And a stiffer spring is in order.

HTH


Hector

Reply
Alejandro O. Martinez
8/27/2016 05:43:49

Hector, I think you'd be doing a great service for the full-power community of Diana 54 shooters by developing the proper spring combination for the ZR Mount that we could purchase from you. Along with the accurizing modifications you've come-up with would serve the purposes of all full-power Air King shooters. As here in the USA, there are more full-power M54 owners versus 12fpe Air King shooters. The availability of an off-the-shelf full-power modified ZR Mount is a marketing void that begs to be filled.

Reply
Marcos
11/11/2016 17:19:32

Hi Héctor, I am just curious.

With your current FAT wrench, same rifle and scope, did you do a comparison about what would be the minimum torque needed on a regular/solid mount?

Thanks,

Marcos

Reply
Hector Medina
11/15/2016 09:35:13

Hello Marcos!

Yes, it is a test I did, but the results are not publishable as they exceed the scope manufacturers' recommendations. So, sorry, I cannot publish those results as it would mean a lot of damaged scopes.
My apologies.




HM

Reply
Brian A. Spinks link
11/22/2017 18:07:24

Hi Hector,
Im reading your old post/s about ZR-1 mount. Mines has worked well although some time ago I cleaned and applied a lighter synthetic grease to the rods as colder weather causes them to slow the action.
Anyhow recently, (1) of the rods, left, has unseated and moved forward in the mount. I can manually move the rod back seating it flush but after several shots it move forward again nearly out from its mount housing. Have you experienced this or have any recommendations how I can seat this flush so it no longer moves from the mount?
There are very few write ups about the Bullseye mount and appreciate your input before I begin to come up with solutions. Thanks in advance. Brian.

Reply
Hector Medina
11/23/2017 13:23:17

Brian,

The screws that affix the rings to the rails are tied screws, #8 if memory serves me right.

Just remove your scope and tighten/snug those screws. If you overtighten them, the mounts will bind, so use blue loc-tite and snug them down in position.

HTH!



HM

Reply
EricS
11/29/2017 09:32:22

Hello Hector,

I'm going through the posts that you have written there and in forums but I didn't find what modifications you have done to do it more repeatable as comming out the factory.
If I understand well, you made a kind of conical ramp for centering it properly, one in the middle or two for rotationnal too? I'm looking forward equiping my 56TH, currently with a 3-9x40 scope mounted on an adjustable mount (barrel droop). It seams the scope is holding well so far and I've got 3/4" groups at 55 yards (but not everytime), 9x is a bit light for doing better ,I'm looking forward to 1/2" groups and I know it's reachable, it's just marvelous to see the pellet going home at 55 yards on the point you want. For doing that, I'm looking for equiping it with a UTG 6-24x50 and I don't want to take the risk of destroying it with it. At first, a Stoeger scope lasted 5 shots and the erector lense came loose (missing loctite...).
I know such scopes are not in the 1500-4000$ price range you listed but its normaly enough for what I want to do. Normaly they are described as airgun proof but I can't figure out such a heavy scope on that scope eater to last long, that's why I'm interested in that mount.

Thanks for your experience so far.

Reply
Hector Medina
11/29/2017 13:10:26

Hello Eric!

Accurizing a set of ZR Mounts is a $70 service we provide if you buy the mounts.
If you want to get the mounts from us, then the Accurized mounts are $140

Sorry that I cannot give you a list of operations, I can tell you that there are 8 different operations that go into making these guns truly FT/high accuracy worthy.

BTW, accurizing the chinese version requires another 4 operations and by then you are far exceeding the price of the originals.

I will be writing an entry on the Ver 2.0. of the ZR Mounts soon. Keep an eye out for it!

Thanks for reading!





HM

Reply
Alejandro O Martinez link
3/3/2018 20:50:35

Over time, I have purchased a couple of Bullseye ZR-Mounts for my gas/metallic springers.
Unfortunately, I've found the scope saddles had to be shimmed to provide enough clearance for the erector.

I'm not comfortable with this arrangement.
Moreover for me, it has become next-to-impossible to confidently determine whether a scope will be compatible with a ZR-mount.
As such, could you establish a list of popular commonly-available optics that can be mounted without any modifications.

This list would be very helpful to those shooters contemplating purchasing a Bullseye ZR-mount.

Reply
Hector Medina
3/6/2018 10:22:40

Hello Alejandro;

The proper way of fitting scopes with large saddles to the ZR Mounts is to mill 1.5 mm's off the watertable.
It is one of the operations that "Accurized" mounts get.

While not ideal, the original intent of the ZR mounts was to house the Bullseye line of optics, and those saddles are 100% compatible.

A list would be almost unending because there are so many variations of all scopes.

I have been working on a complete redesign of the ZR mounts that will do away with most complaints, I will discuss it over in Germany next week.

Keep well and shoot straight!


HM

Reply
Jeff Carbine link
1/26/2022 07:37:51

I appreciate that you explained this gap allows the piston to reach the end of the compression chamber and the pellet to depart BEFORE the scope is harmed. My best friend is looking for some info, this should help him. I appreciate that you helped me learn more about the scope.

Reply
Hector Medina
1/26/2022 14:57:07

Glad you liked the entry, Jeff!

Thanks for reading!




HM

Reply



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    Hector Medina

    2012 US National WFTF Spring Piston Champion
    2012 WFTF Spring Piston Grand Prix Winner
    2013 World's WFTF Spring Piston 7th place
    2014 Texas State WFTF Piston Champion
    2014 World's WFTF Spring Piston 5th place.
    2015 Maine State Champion WFTF Piston
    2015 Massachusetts State Champion WFTF Piston
    2015 New York State Champion WFTF Piston
    2015 US National WFTF Piston 2nd Place
    2016 Canadian WFTF Piston Champion
    2016 Pyramyd Air Cup WFTF Piston 1st Place
    2017 US Nationals Open Piston 3rd Place
    2018 WFTC's Member of Team USA Champion Springers
    2018 WFTC's 4th place Veteran Springer
    2020 Puerto Rico GP Piston First Place
    2020 NC State Championships 1st Place Piston
    2022 Maryland State Champion WFTF 
    2022 WFTC's Italy Member of TEAM USA 2nd place Springers
    2022 WFTC's Italy
    2nd Place Veteran Springers

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