Review – Atom Optics 4-16×40 AO – Part 2

Welcome to Part 2 of my Atom Optics scope review. Firstly I have to apologise that it has taken so long. With a full time job, shooting and writing other posts it has taken a while to put it together. But I got there in the end, so I hope you enjoy reading it.If you haven’t seen the first half of this review, please see the link below. This review is of the Atom Optics 4-16×40 AO IR scope, sold by In Your Sights. RRP is £49.99 at the time of writing.

Part 1

Previously, I mostly looked at the technical details of the scope. Part 2 is a bit more subjective, but I’ve tried to stick to the facts where possible. Some of the tests rely on my ability as a shooter (which can be questionable) so take these with a pinch of salt if needed.

The topics to be covered are:

  • Bolt quality
  • POI tests
  • Is it shockproof?
  • Is it fogproof?
  • Can it be used for HFT?
  • Conclusions
  • What will happen to the scope now?

Part 2

Bolt Quality

It’s fairly common to swap scopes between guns, so the bolts will be torqued up and loosened again more than once in their life. With budget scopes you often hear of people struggling with ‘screws made of cheese’. So I thought I would test how many times the provided mounts can be fitted, by doing them up a few times.I did one of the dovetail screws, and one of the top clamps, 50 times each. This might be excessive but I’m sure some people manage this very easily. In each picture the left side is one or two uses, the right side is 50+ uses.

You can see the paint was taken off from underneath the bolt on both the fixing plate and the bolt head itself. However I had no rounding of the heads at all. I’m sure these could be taken off and on many more times without issues.
(This is assuming you do them up to a sensible torque. I did the top clamp screw to 2Nm, and the bottom rail screw to 5Nm. Check the manufacturers specification, but this is what I always use).


POI Tests

This section will test whether the scope retains it’s zero during normal use. Any problems will be shown as the pellet shifting its point of impact (POI). Worst case, the reticle lens will detach itself and start spinning round. This is game over for a lower cost scope, as the cost of fixing it would be way above the actual value.
Each sub-section is an individual test. I would consider all of these normal use, so it needs to pass all of them!
To start with, the scope was mounted to my Original (a.k.a Diana) 66. In my opinion one of the greatest, and best engineered, spring powered airguns ever conceived. Designed purely as a 10m target gun, the power output is under 6 ft-lb (half the UK legal limit). However the twin piston-recoiless action, match grade barrel, and match trigger rival anything made today.
In short, this gun is perfect for testing accuracy and highlighting any issues.

For this, the magnification was set to 6x and the zero checked.  Then adjusted through it’s full range of motion, then set to 10x for Test 1. Then the process was reversed to through the range of motion again and set it back to 6x for Test 2.

Objective Lens
Similar to before, but this time the objective lens was adjusted. Initial zero was checked at 15 yards. Then adjusted through it’s full motion (from 10y to infinity). Test 1 was performed at 10y parallax. Test 2 was done at 20y parallax.

Ocular Lens
Same story as above. Zeroed at 50% out. Then tested all the way in and all the way out. (Ignore the odd shot here, I pulled the trigger too soon by mistake).

Known by a lot of people as the ‘box test’. The idea here is simple. Check zero, then alternately adjust the windage and elevation turrets by a set amount. I chose 20 clicks right, then 20 clicks down, 20 left, and finally 20 up. If all goes well, the final shot will go through the same hole as the first shot.
So the top left hole has 6 shots through it. The other corners have 3 shots each.
As a further test, I did a further 10 clicks right and down to see how close to the middle of the box the pellets ended up.
Again, ignore the odd shot in this one

I will be the first to admit that this test is not perfect. It relies quite heavily on my shooting. Hence why I chose the gun I used in the first place. However even with me behind the trigger, you can see that the zero never significantly shifts in any of the tests. I would go as far as to say that it didn’t shift at all, and the errors were all mine. 



This is the part the springer shooters will be scrolling down to find. Will this scope be able to withstand the double-recoil abuse, of a spring powered airgun?
There were several tests here. The first was to mount the scope to a suitable rifle and rattle through a tin of pellets. I don’t have a firearms certificate, so all my springers are sub 12 ft-lb. However, as I’ve mentioned before, I try to concern myself with HFT and helping beginners to the sport. HFT is limited to 12 ft-lb so this is still a very relevant test.

I may not have an FAC, but I do have a decent selection of ‘big springers’ to chose from. My HFT TX200’s are a bit tame compared to a lot of springers, so I needed something that would be a real test. In the end I settled on the big Weihrauch HW80k. This is a full 30mm piston version putting out around 11.5 ft-lb. If anything in my collection was going to break the scope, this would be it.

The test was simple. Fit the scope and zero the gun. Then shoot a load of pellets over the course of a few weeks. After a full tin of 500, check the zero again to see if it has shifted. And also check the reticle is still straight and looking good.
This has been a bit slow going because I’ve mainly been practising with my TX200 for the HFT competitions, but I got there eventually. The result is….no noticeable issues. The reticle hasn’t dropped or spun round and none of the adjustable parts have come loose. So far the claim of shock proof is holding up. 

**Bonus Round**
I had forgotten about my FWB 300. This 10m gun is only 6-7ft-lb (depending on pellets used) but it has a lot of recoil. The shooter doesn’t feel this because of it’s sliding sledge system which isolates the action from the stock. However as the scope is mounted directly onto the action, it is exposed to all of the recoil PLUS the additional shock of the sledge system. I have no idea if this would be tough on the scope, but I’ve heard of the similar Diana Airking system being a scope-breaker.

So for the bonus round, I put another 50 shots through the FWB 300 with the scope attached. After I set the zero and tried to make a smiley face on the card (wasn’t very good). I also tried a 30 shot group. To be fair this was rested and only 10m away, but look at it. Clearly no scope issues going on here.

I was thinking about a further shock test (i.e dropping the scope on the floor). But I’ve had a change of heart. I just don’t think this is a suitable test unless I know the exact G force shock load that the scope is rated to. Knowing this, I could use the mass of the scope and some maths to calculate a height to drop the scope onto a hard floor. 
I can’t speak for every HFT shooter, but I am very careful with my kit. Touch wood, I haven’t ever dropped a scope or banged it on a tree etc. The springer test is enough for me. Let me know if you disagree.


This was the least scientific of the tests, and I had a problem trying to perform it. Any glasses wearers (like myself) know full well how to fog up lenses. Stand out in the cold for a while to get the glass nice and cold. Then step back into a warm house. The moisture in the warmer air rapidly condenses on the cold glass, and hey presto, fog!
The term ‘fogproof’ in the context of scopes means the INSIDE lenses of the scope won’t gather any condensation and will remain perfectly clear. This is achieved by removing all regular air from inside the scope, and replacing it with Nitrogen. This contains little to no moisture. If there is no moisture, then there can be no condensation. Simple.

In the end the best test I could come up with was the following. Leave the scope in the fridge overnight. The next day, take it out and put it on the radiator when the heating comes on. Wait for the outside lenses to fog up (because they will). Then give the outside lenses a wipe with a clean, dry cloth* and have a look through it. If you have properly wiped the outside glass but can still see fogged up lenses, then it must be on the inside.
Each time I tried this, the scope looked fog-free. I know the temperature change was sufficient, because I got fog on the outside.

Another accidental test happened today. I was shooting with the FWB300 outside in the snow. When I came back into the house, the metal action of the gun was soon covered in condensation. I wiped the scope lenses and had a look through. Nothing. Clear as they always have been.
(To the gun collectors out there don’t worry. The FWB action came out the stock and got a clean, and is now propped up next to the radiator).

This test essentially shows two things:

  1. The scope was definitely nitrogen filled at the factory
  2. The nitrogen hasn’t managed to escape, therefore the scope is well sealed


Can it be used for HFT?

This is the big question that I have been working towards over this two part review. Up to this point, I have mostly been testing the specification of the scope and if it meets the manufacturer claims. However suitability for HFT is a bit more subjective. Some important points for me are below:

Can you focus, and range find?
For this I set the scope to my preferred parallax adjustment. That is around 23 yards. On my HFT scopes I find this gives roughly equal levels of blurriness between the close and far ranges. i.e 8 yards is about as blurry as 45 yards.
Once it was set to roughly 23 yards parallax, i tried shooting at 8 yards. The default view for my eyes is usually the target in focus, and the reticle blurred out. It was the same story through this scope. The trick is being able to bring the reticle in and out of focus, in order to line up your holdover to the kill zone.

Initially I tried focusing on the mil-dots, but whatever I tried, they just wouldn’t come into focus. Then I tried using the thicker bars of the reticle beyond the mil-dots. This did the trick and the reticle came into sharp focus. Then overlay the appropriate mil-dot with the target (or where the target was before it went all blurry) and fire. Three shots attempted and all three went in the same hole. I would call that a success. 

Focusing out to 40 and 45 yards was much easier. Here I could focus on the mil-dots themselves instead of the thicker bars. This probably means I could set the parallax a bit closer, maybe 20 yards and make the closer targets slightly easier. Either way, I was able to focus on the target.

The amount of ‘blurriness’ is also very subjective and can depend a lot on your eyesight. But this scope seemed almost on part with my other (more expensive) HFT scopes. On my competition set-up, 20 yards to 30 yards is crystal clear. The Atom Optics scope was the same. However when it started to lose focus past 30 yards, it happened faster than I expected. So 40 yards through the Atom Optics looked like 45 yards through my HFT scope. To be honest you could get used to this and still use it help your range finding. But it does make the 8 yard and 45 yard targets slightly more difficult to see.

Parallax error?
Yes, there will always be a degree of parallax error in HFT, purely because you cannot adjust the scope. I’m no expert on scopes so I won’t be able to explain the following statement, but this is what I found.

Parallax error was pretty much as I expected at every distance, except 10 yards or less. With a 23 yard parallax the very close targets had more parallax error than I am used to. Essentially I got the crosshairs on target then moved my head around to see how much the crosshairs and the target diverged from each other. Done back to back with my normal scope, the effect was more pronounced through the Atom scope, compared to my usual one. The image also got quite distorted if I moved my head too far. BUT (and this is a big but) I was actively trying to cause this problem. I had to move my head a long way for this to happen, and in all of my other tests I didn’t get this problem. So this is almost a moot point.

Again a subjective test. I stood with my back to the sun and looked through three scopes in turn. The £50 Atom Optics on test here, my usual £150 HFT scope, and my new £300 (possible future HFT) scope.
Yes the view through the Atom Optics scope was more washed out. Was it 3x or even 6x worse (as the price differences might suggest). No not really. It was still a usable image and better than some I have seen.



One of the main topics I wanted to convey in this (mostly) technical review was if the Atom Optics 4-16×40 AO IR was fit for purpose. That’s why I focused on testing the manufacturer’s claims. At this point I can say, yes it is. The scope passed almost all of my tests with flying colours. With the exception of the magnification test in Part 1. It couldn’t match the more expensive scope for performance there but it was leagues ahead of the £30 scope I tested at the same time. Max magnification was around 15x instead of 16x but I think you would be hard pushed to notice that in real world conditions. 
The scope seems well put together. The adjustments are easy enough to use and the nitrogen seal is good. The recoil test shows that it should be able to  handle the recoil of most springers you would use for HFT**, and there was no POI shift in the time I had it.
Based on the above I would say yes, it is definitely fit for purpose.

The next question would be, could you use this for Hunter Field Target? Again I would say yes. The scope functions perfectly well out to HFT ranges (this is the furthest I tested). All the required adjustments are there and it has suitable magnification. The parallax setting works well and range finding based on ‘blurriness’ is definitely possible.
I can’t see any reason this scope wouldn’t be suitable. Based on the specification (4-16×40) I would also say this is the most suitable out of ‘In Your Sights’ current range. If you want to buy an HFT scope from them, this is the one.

And finally, who would I recommend it to? Personally I won’t be using this scope for HFT but for two very good reasons. Firstly I really like having half mil-dots on my reticle and use them extensively. This scope only has full mil-dot. Secondly my other two scopes do a slightly better job of dealing with bright sunlight. However this is reflected by the price I paid for them.

I think this scope is perfect for the following shooter. If this description sounds like you, then put this on your list of options to consider:

  • You have an entry level airgun with the usual packaged 3-9-40 scope (or no scope at all)
  • You are starting to get into HFT and you want to upgrade your scope so you can play around with magnification and parallax settings
  • You don’t need half mil-dots (lots of people don’t)
  • You prefer a fine reticle
  • You have a budget of up to £100 for a new scope 

If I had to pick a reason not to recommend this scope it would be that the reticle might be too fine for some people. This is down to personal preference so it’s hard for me to say. Personally I think the fine reticle on this scope is it’s stand out feature compared to alternatives in the same price range. To me this represents really good value for money, and I haven’t used anything else the same price that I would choose over this.

What happens to the scope now?

Well the very kind people at In Your Sights have said I can keep it for long term testing. I want to extend that offer to you. So this is the plan. If you are just getting into HFT and don’t have a suitable scope. Come and see me at any of the competitions or practice days I shoot at, and let me know you would like to borrow it. You can then use it for the next 3 months. I only have 3 conditions:

  1. At the end of your 3 months, you write a short review for this blog. It can be as little or as much as you want. But just let us know how you got on with the scope and with HFT in general. Did you enjoy HFT? Will you be continuing? etc etc
  2. Please look after it for the next person
  3. Have fun!

If you are interested, check my Facebook page CLICK HERE for updates. If you are very new to the sport, we can always find someone to shoot the course with you, so you can pick up the scope and go round a course on the same day.
Priority will be given to juniors (they have the lowest budget after all).


So that’s it. Review over. I’ve learnt a lot about scopes during the course of writing this review, but I am very far from an expert still. Although I enjoyed the opportunity to have a go, I did struggle with it. I might come back to scopes in the future. But I think for now I will continue to explore other directions for the blog.

A final big thank you to ‘In Your Sights’ for giving me the opportunity to do this test. The scope can be purchased from them using the following link. Remember, using code TheAirGunBlog119 will get you 10% off anything on the site.


*It’s very important that you use a very clean cloth. Preferably one that doesn’t get used for anything else, and is stored properly between uses. Using any old cloth can result in damage to the lens coatings

**I wasn’t able to test a gas ram, or the big Diana Airking. Results may vary with these.

Disclosure. I did not pay for this scope out of my own pocket. However I am not associated with In Your Sights, and am under no obligation to write a ‘good review’. The opinions expressed are my own genuine thoughts.

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