









🎯 Lock your target, own the moment with MonstrumGuardian AO
The MonstrumGuardian Series AO Rifle Scope offers versatile 3-9x magnification and an adjustable objective lens to eliminate parallax, ensuring razor-sharp focus and accurate range estimation up to 600 yards. Built from aircraft-grade 6061 aluminum with a nitrogen-charged, sealed tube, it delivers rugged water and fog resistance. Precision 1/4 MOA windage and elevation turrets with locking features guarantee reliable adjustments. Complete with high-profile Picatinny/Weaver rings and flip-up lens covers, this scope is engineered for professional-grade performance and durability.






| Brand | Monstrum |
| Color | Black | Picatinny/Weaver Scope Rings |
| Style | Guardian | 3-9x40 AO |
| Sport | Hunting |
| Item Weight | 15 Ounces |
| Material | Aluminum |
| Magnification Maximum | 9 x |
| Objective Lens Diameter | 50 Millimeters |
| Magnification Minimum | 3 x |
| Compatible Devices | Rifle |
| Mounting Type | Weaver Mount |
| Night vision | No |
| Model Name | SG3940AO |
| Manufacturer | Monstrum |
| Reticle Type | Crosshair |
| UPC | 810088810800 |
| Item Package Dimensions L x W x H | 15.79 x 3.5 x 2.95 inches |
| Package Weight | 0.83 Kilograms |
| Brand Name | Monstrum |
| Part Number | SG3940AO-B |
| Included Components | Guardian Scope, One Pair High Profile Scope Rings, One Pair Spring-Loaded Flip-up Lens Covers |
S**
Best Optic For The Money...Period
Purchased a Ruger Precision .22lr to see if I liked the platform before I went with it for a 6.5 Creedmor. As the RPR .22 was only $350 I felt a little silly mounting a Burris or Leopold optic on a range toy. Saw the reviews on the Monstrom sights and figured for this price I would be getting an optic with lots of corners cut in build quality and components. It's cheaper than a box of good ammo so I really thought this would be on my rifle for one range trip then end up in my box'o'' old parts.Well I was surprised by the build quality. The tolerances on the tube, adjustment points, and even the mount felt and looked really good. Optic is a bit heavier than the specs but I will let that slide as it's a couple ounces. The glass that I thought would be super cheap with irregular appeture and poor clarity was pretty clear. This does not have the pristine image and sharp clarity of a Leupold's VX entry optic but you are paying $300 less. I have ZERO complaints about the quality and construction of this optic for less than $60 bucks. It exceeded my admittedly very low expectations by a wide margin.The reticule is also very basic and the manual did not provide adequate explanation of the mils appropriate caliber and load to provide what I think is a requirement for this style reticule.Don't think your getting a true FFP range finder finders on this glass. But, again it's a 50 dollar scope you shouldn't. The AO dial did allow a guesstimate of the distance to target by assessing the optical sharpness. It is a feature that you really should not see at this price point and it works. That is probably because the biggest surprise of this optic was the glass. It is not just adequate I would definitely say it is very good. The parallax adjustment was not spectacular but was comparable to what I would expect on a mid range Burris or Vortex. Bottom line it's good glass that allows for an adequate range calculation and provides a more than adequate visual acuity even at 9x. Again, I have seen better but this is the best glass and controls you will get for the moneySo I mounted this shockingly good quality optic to the Ruger and headed to the range. Mount was super easy, it's a picatinny if you can't figure it out you should not be playing with a firearm.So I started at 100 yards and was off paper the first shot at min magnification. Turned the elevation and windage dials one rotation unit each and missed again. Gave them a couple more twists and I was on paper. Took a couple shots to figure out the mils, which are set to I think62 grain 5.56 or .223, definitely not a .22lr. I took a couple more shots from a full mount and got the feel for the reticule mils and the drop on the Hornady .22 I was firing. I pulled back to 50 yards and found zero in a 3 shots Pushed back out to 100 and was able to get a good zero after learning the system and adjustments. The Optic was a bit more than the round I was shooting should have so I put that on me underestimating the Scope. Windage and Elevation have nice firm click and resistance. Once you know what a rotational unit is going to do this optic is easy to zero. The Mag and AOcontrols worked well and the parallax was minimal. Eye relief was excellent. I was shooting a bolt action precision chasis rifle so recoil was almost non-existent. That said this optic easily held zero over probably 200 shots that day.The caps were ok more than I expected but the cheapest feeling component of the system.I have to say I was blown away that a scope with the quality and accuracy of this optic was in junk toy scope price range. Is it a $2,000 scope NOPE. It is comparable or better than many $300 - $500 dollar optics I've had from Burris and Vortex. Best damn scope I've ever used that was $50 bucks without a doubt.The Monstrum never went in the box'imparts it is still on the Ruger. Shoots great. For the money this is a no brainer and could easily be used with .223 or .270. I'm not sure how it would handle .308+; but it probably would hold a zero and be a great optic for hunting open terrain.I can't say this and mean it more, if your learning to distance shoot this is would be a great way to learn fundamentals. Without breaking the bank. A low end Rem 700 and this scope will leave you hundreds to spend on instruction and practice ammo. It exceeds all expectations and will give you a scope that feels and performs like one that is 6 times it's price.The best optic for your money period. Just don't put one on a Ruger Precision because that is a crack gun and gets you hooked fast and will quickly result in desire for one of his big brothers.I really loved the chasis and trigger and shockingly the optic.I have subsequently added a Alpha FFP1x6 24 to an AR race gun that my buddies all admitted shot as well as their $600+ FFP's.Beginning distance shooters can't go wrong with this high value optic you won't be out shooting your glass anytime soon. Seasoned shooters looking for a bargain or a practice rifle scope will be pleased as well.This optic changed my old rule the optic should be at least the cost of the rifle and double or triple if your going to 1,000+ shots. I can assure you this rifle can out to 200 yards with quality .22lr. It's the round not the optic that is limited the range and the optic was 1/8th the price of the gun.When I get the Ruger Precision in 6.5 I will likely give a G3 Monstrum the first crack at the picatinny rail. That will buy me a ton of rounds to enjoy the gun over the Leupold I would have been saving for months to buy.Fully recommended not just a good scope for the money but just a good scope period!
O**S
Great scope for the money
Clear and easy to zero .
B**K
If you're precise with the eye relief, it can be very accurate.
Clarity, eye relief, reaction to adjustment and light gathering ability are all pretty surprising for the price. While there is a large range of eye relief, about 80% of it is super sensitive to parallax variances. If you keep in the 20% sweet spot range, the accuracy is quite pleasant. I'm using it on a Hatsan Jet 1 in 22cal with round nose 16.08gr Dead Center pellets and with care, getting groups as shown above. This particular result was on the second of three magazines of seven at 25 yards. I first tried another budget scope and was horribly disappointed.
J**S
Excellent value
Having used Monstrum products in the past, I had confidence that this scope would not disappoint. It has the features I need for its purpose which is going on a heavy barrel 22lr. Good magnification range and adjustable parallax is what I need.
M**T
Excellent Scope
I don’t think it is possible to get a better scope for the money. When my scope was delivered, I was amazed at the quality and features it had. Unfortunately, there was a defect in the scope where something was obstructing the view inside the opticals. I set up a return with Amazon and had a new scope delivered in 3 business days. I could have returned this scope and then bought a different one but I liked the look, the feel, the optics, the lighted reticles and the price. I also really like the lens covers as well. Mounting the scope was easy and the mounting hardware is excellent quality. This scope is perfect for my little .22 rifle and is easy to set up and sight in. The objective control and magnification controls are not the smoothest I have ever used, but the optics on this scope are quite simply amazing for the price. You really cannot go wrong with this scope!
A**E
Wouldn’t hold zero. Update
The glass is nice and clear, great functions and solid price point, also looks great on my 10/22…. However I took it out to zero it and to no avail it will not hold zero. Tried multiple types of ammo and different rifles. I’ve messaged the manufacturer so we will see if they make it right. If so I will update with my findings.UPDATE: Manufacture was great to deal with. They sent me a brand new optic and it holds great. Awesome product for the price.
G**L
MONSTRUM ALWAYS PROVIDES QUALITY AT AN EASILY AFFORDABLE PRICE!
My Monstrum Guardian Series AO Rifle Scope with Parallax Adjustment, is a Second Focal Plane scope (my preferred Focal Plane for long-range shooting [750yds+]). The glass is perfect (clear, sharp presentation of illuminated crosshairs, and no halo or fog), and the 1" tube is solid and well made. The 1/4 MOA/click windage and elevation adjustable turrets have screw-on covers to keep your adjustments secure once zeroed, and the clicks are smooth and positive. I have a couple of scopes costing 10 times more than the Monstrum Guardian Series AO Rifle Scope, and I bought it "just to check it out" because of the low-end price. I have used several Monstrum cantilever mounts, and other Monstrum products which impressed me enough to try their optics, and the Monstrum Guardian Series AO Rifle Scope with Parallax Adjustment surpassed my expectations. Monstrum provides an outstanding scope at a bargain price in the 6-18 power range. You are reading this review, and I have NO association with Monstrum other than as a customer, so if you're looking for a 6-18 variable optic, I STRONGLY recommend the Monstrum Guardian Series AO Rifle Scope! If you don't like it and bought it from Amazon, you can return it for credit or replacement.
C**O
Good for the money
For the money; very clear. Clear and no distortion at 9x. Appears to be good qualityClock adjustment are not tactile and responsive. Takes many rotations on the elevation just to move a couple MOA. However holds zero in my savage 64 fvsr 22 long rifle
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