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Umarex Fusion CO2 rifle: Part 4

by Tom Gaylord, a.k.a. B.B. Pelletier

Part 1
Part 2
Part 3

Umarex Fusion rifle
Umarex Fusion CO2 rifle

Today is the first accuracy test of the Umarex Fusion CO2 rifle. It comes one part late because we spent time looking at the CO2 cap, the adjustable trigger and the power adjuster in Part 3. The power adjuster is straightforward — twist the screw in and increase the striker spring tension to increase power. The trigger, we learned, is adjustable, but the safety slider prevents a very wide range of adjustability. You can modify it if you choose, but I don’t recommend it; and it will void any warranty on the gun. Blog reader mikeiniowa explained how it’s done, but he said to use caution — and I don’t intend doing it to the test gun.

You should now understand how the CO2 cap works, but there’s one additional thing that I think needs to be stressed. The gas exhaust screw on the cap is to use after the CO2 has been depleted. Screw it in and exhaust the remaining pressure. But that isn’t the end because the cap still cannot be taken off safely, as a reader mentioned yesterday. The o-ring that absorbs gas has to be given a lot of time to exhaust that gas and shrink back down to normal size before you attempt to remove the cap. If you try to remove the cap too soon after exhausting the gas, the o-ring will still be swollen and tightly wedged in place. You could tear it if you use too much force on the cap. So, let an hour or two pass before you try to remove the cap; and leave the exhaust screw screwed in, so the remaining gas that leaves the o-ring can get out of the gun. Anyone who has ever owned a Schimel CO2 pistol knows what I am talking about because they had the same problem.

Mounting the scope
The Fusion comes with a 4X32 scope and rings that must be mounted on the gun. The rings are made to clear the rounded receiver top, so don’t think just any rings will work. I want to show you what one of the rings looks like after installation, so you don’t go nuts thinking it’s not on the gun squarely.

Umarex Fusion rifle scope ring
The Fusion receiver is rounded on top, so the bottom of the scope ring must be profiled to clear the hump. The rings that come with the gun are correctly shaped for this. Don’t let the cockeyed jaw piece fool you — this ring is on the rifle straight and tight!

The scope caps have 2 screws each, which is perfect for this gun. There’s no recoil, so 2 screws hold the scope tight enough for good accuracy.

Once the scope was mounted, I sighted-in at 10 meters. All of today’s shooting will be from 10 meters for reasons I will explain as we go. I’m telling you that because the groups will be smaller than if they were shot at 25 yards. I do plan on testing the Fusion at 25 yards, too, but first I have to establish what it can do closer.

One additional thing about the sight-in. All the pellets struck the target low at 10 meters. I accepted that for the whole test, and I had to adjust the scope up very high to even get that. You know how nervous that makes me! So, at the end of this test I’ll shim the rear scope ring and try one more group with the best pellet. The groups you’ll be seeing are either low on the bull or just beneath it.

JSB Exact RS
The first group was shot with the JSB Exact RS pellet. As I shot, I could see all the pellets going into the same place; although with the 4x scope, it wasn’t easy to see exactly how good it was until I went downrange. It turned out that 10 pellets made a 0.286-inch group, measured between centers. And this group is very round, which is a good sign that everything is right with the rifle.

Umarex Fusion rifle JSB Exact group
Ten JSB Exact RS pellets made this 0.286-inch group at 10 meters. Remember — this is only 10 meters, so the groups are going to be smaller. But this is a great group!

I observed several things while shooting the first group. The first is the trigger, while having a very long second stage pull that you can feel, is very controllable. Next, I did find the rifle just a bit fiddly to load. Once I got the hang of it, however, I was able to load pretty fast. But the pellets tend to flip around in the trough — especially the domes!

And, finally, I noted how very quiet the Fusion is! Our female cat, who usually walks around the house complaining every time I shoot, found it hard to hear what I was doing unless she was in the room with me. Even then, the noise didn’t seem to bother her, though Edith did say she walked into her office to complain once. Other than that, she was quiet. I think any apartment-dweller could shoot this rifle indoors without bothering the neighbors.

H&N Baracuda Match
Next, it was time to test the H&N Baracuda Match pellets. They landed higher on the target than the RS pellets but were still below the point of aim. This group measured 0.345 inches and was just as round as the RS group.

Umarex Fusion rifle HN Baracuda group
Ten H&N Baracuda Match pellets made this 0.345-inch group at 10 meters. Once again, the group is round and quite small.

Crosman SSP hollowpoint
Then I tried the lightweight lead-free Crosman SSP hollowpoint. I didn’t expect much from these pellets, but I tried them because I’d used them in the velocity test. They produced a 10-shot group that measures 1.66 inches between centers. Obviously, I’m not going to shoot this pellet at 25 yards and risk hitting the walls of my house or the furniture! This is why I started shooting at 10 meters.

Umarex Fusion rifle Grosman SSP hollowpoint group
Ten Crosman SSP hollowpoint lead-free pellets went into 1.66 inches at 10 meters. Several seem to have gone through while tumbling. Not the pellet for the Fusion!

RWS Hobby
The last pellet I tested was the RWS Hobby wadcutter. Ten went into 0.59 inches at 10 meters. But the first pellet went to the left of the next 9, so I think this might be one of those times when conditioning the bore was required for best results. Not that I believe in that theory, mind you, but this time it really looked like that’s what was happening. The 9 pellets went into 0.36 inches — a much better showing! The Hobby is the third best pellet in the test, but I think the group of 9 is more representative of what it can do.

Umarex Fusion rifle RWS Hobby group
Ten RWS Hobbys went into 0.59 inches, but the last 9 went into a much tighter 0.36 inches.

The JSB Exact RS and the H&N Baracuda Match are the 2 pellets I’ll test at 25 yards. I would include the Hobbys, but 25 yards is right where wadcutters start to spread out, so I’ll just go with the 2 domes. However, there’s still one more thing to try today.

I removed the scope and put one plastic shim on the bottom of the rear ring under the scope tube, then installed the scope again. I went back to 10 meters without any sight-in shots and shot one more group with JSB Exact RS pellets. The group moved up over 1-1/4 inches and over to the left by a half-inch. This is where I will begin shooting at 25 yards, knowing that I’ll probably need to decrease the elevation to get back on target. Isn’t that interesting, that the point of impact moved up so much with a single shim? The shim measured 0.013 inches, by the way.

Umarex Fusion rifle JSB Exact group after shimming
Ten JSB Exact RS pellets went into 0.244 inches at 10 meters. It’s the best group of the day! This group was fired after a 0.013-inch shim was placed between the scope and the rear ring. The scope was then simply remounted and no sight-in was done. This group is about 1.30 inches higher than the first group. It also appears to be smaller, but the dark paper hides the true size of the pellets.

Impressions so far
The Fusion is a winner! I like everything about it. It has taken some time to understand; but now that we’ve been through the design and know what to expect, you show me another air rifle that costs $170 and shoots like this one. We’re talking groups very similar to what vintage 10-meter target rifles can produce.

No — it’s not a good rifle for hunting; and, no, I don’t think it can be modified to become one. If that’s what you want, get a Discovery. Leave the Fusion as it is — a nice, quiet, accurate rifle.

25-yard testing yet to come.

95 thoughts on “Umarex Fusion CO2 rifle: Part 4”

  1. B.B.

    That would make a good starling popper in a relatively small back yard . It has enough zap for it.
    I think that 25 yds would be about max for it if it can hold a good enough group that far. Not going to be much good in the wind, though. About like me shooting an R7 or the T200 out back . Light or no wind duty.


  2. ‘You show me another air rifle that costs $170 and shoots like this one’.
    The venerable QB78 cost 40% less and made in China. AND, you don’t have
    to deal with Umarex’s customer service.

    • Eddy,

      I knew I was on thin ice the minute I said that. Okay, SOME QB78s may be this accurate, but others are not. Their problem is inconsistency. Of course I don’t know what the Fusion will be like in that respect, either.


      • Or you just pay the extra $10-$20 for “gold service” and the company you’re buying from quality tests your QB78 for you to make sure it is performing within advertised specifications. (And if it isn’t they either fix it or send you another gun that does perform within specifications.)

      • B.B.,
        I am a long time air gun accumulator and shooter and have enjoyed your blog. I would like to ask you a question, and forgive me if this is not the right place to do it. I have been looking for a quiet and accurate air rifle for sometime. I live in a subdivision that is surrounded by canyon walls. Consequently, you can hear neighbors normal conversations outside and the report of an air rifle would be heard by everyone. I have turned a storage room into my shooting range. I still have to be careful of noise to keep from bothering my wife. So, the rifle I want has to be accurate, very quiet and be able to be used in a room 15′ deep. I can get 15 meters by shooting from an adjacent room into the air gun range. I shoot mostly pistols and have a fine collection that I have purchased from Pyramyd Air. I have an HW77K that I purchased in the early 80’s. It has a Beeman 2X7 Blue Ribbon scope. I can not adjust the scope to be used at both 15′ and 15 meters.

        Back to the reason for my e-mail. I have purchased a new Umarex Fusion from Pyramyd Air and should have it in a day or two. I would like to also get the Leapers Bug Buster 3X9 scope to replace the 4X that comes with it. The Bug Buster can be focused to 3 yards, so should work great for me. My question is will the quick attach scope rings that come with the Bug Buster scope, work on the Fusion? In your review, you mentioned that not all rings would work on it because of the rounded hump they have to straddle.

        I read your blog everyday and look forward to it. Thank you for that great service.
        Jerry in Texas (fasride)

    • Another economical choice would be the 2250 from Crosman’s custom shop or build one from a 2240 from PA and parts from Crosman. It will do everything a QB-78/79 will do and do it on ONE CO2 cartridge.

  3. Now THAT was worth the wait this morning! Accuracy like that makes things like that finicky CO2 cap forgivable. It’s accurate, cheap and quiet. What a great combo. If only it was available here, that’s all I want in a rifle (it could also look good but then it probably wouldn’t be cheap).

    In the first paragraph it says ” twist the scvrew” I think it’s supposed to be “screw”, that’s what happens when you proof read while being sick. Get some rest Edith.


  4. Caliber: 0.177″ (4.5mm)
    Velocity: 750 fps
    Loudness: Our female cat, who usually walks around the house complaining every time I shoot, found it hard to hear what I was doing unless she was in the room with me. Even then, the noise didn’t seem to bother her, though Edith did say she walked into her office to complain once.
    Barrel Length: 17.13″
    Overall Length: 40.1″
    Shot Capacity: 1
    Barrel: Rifled
    Front Sights: None
    Rear Sights: None
    Scopeable: 11mm dovetail
    Buttplate: Rubber
    Suggested for: Plinking & target practice
    Trigger Pull: 3.0 lbs
    Action: Bolt-action
    Safety: Automatic
    Power Plant: CO2
    Function: Single-shot
    Body Type: Rifle
    Fixed/adj. power: Fixed
    Weight: 5.71 lbs


    lololos, a new loudness scale. With a real loud rifle: Momma cat spit up a fur ball and ran up the curtains.

  5. Hi Tom
    This gun is really impressive! I hope it comes to South Africa. One question: Any possibility of bringing out a version with a wooden stock? I think it will look great with a nice light-colored wooden stock – not a dark stock like the Xisico XS60C.

  6. Just got my Fusion in today! What an awesome rifle, I tested my accuracy at 20 yards and got one ragged hole with a fly, using RWS Dome.

    Thanks you Tom for doing the review.

  7. I disagree with Tom about whether this gun is a winner. That’s because if you have to wait a couple hours to put more co2 in the gun that rules it out as a plinker or any other activity that has a high shot volume. And since co2 guns are traditionally used as plinkers because they don’t need pumping or cocking a mainspring… It would be a winner if it didn’t use a cap system that prohibits quick recharging.

    • J.
      I was just going to make a similar post.

      Wait 2 hours before I can shoot the gun a gain. That is a Big Big turn off for me.

      And I’m with you J. If they would of used something more modern on the gun just as you said It would be a winner.

      But maybe not. The 10 meter shots look good. But the 25 yard shot. What the Heck!

    • J.,

      The 2-hour wait is as bad as it might be. I didn’t actually test this rifle. I have owned a number of vintage rifles that had similar o-rings and that’s what they took.

      Maybe I will test just that aspect of the gun for next time and include the results in with the 25-yardv accuracy test.


      • Why not just replace the O-ring in the cap from the start with a decent one. Measure the one on the gun ‘s cap before you gas it up. I use a hard Viton #113 for the cap O-rings on the old Crosman 160’s,180″s ,150’s ect… Ten bucks will get you a lifetime supply. What size is this one? BTW, the Crosman 150 I soaked with the Bars Trans stop Leak as you and Dennis Q suggested,is still holding ,AND(!) the O-rings I ‘m still soaking in the stuff for weeks haven’t turned to goo.

        • Actually Robert, I’m not sure that would work. My understanding from what Tom has said is that the O-rings on the cap swell to achieve a tight seal when exposed to co2. Measuring them before they swell would mean that the O-rings you get would be too small to produce a tight seal. And if you bought O-rings sufficiently large to produce a tight seal, the cap probably won’t go on or come off without tearing the O-rings.

          • J: If the O-ring was made from the proper material and size, you wouldn’t see excessive swelling of a too soft material that was so permeable that the cap O-ring was distorted, resulting in hard removal .What I see is that over time is the O-ring will absorb CO2 until it becomes so distorted in regards to itr’s original size, that it never returns to it’s original size and becomes useless . It will then be damaged from repeated removal and leak when charging the gun.

            • Robert,

              If I’m reading this correctly, the O-rings do not swell excessively. They swell to the correct diameter to seal the gun and when degassed return to the correct diameter to open the gun. As for the other, perhaps Tom can comment on whether these types of O-rings permanently swell.

              That said I agree though that a more modern O-ring design would improve the gun. However I don’t know that you can simply swap out the current O-ring for a different kind and still have it work. That was the intent of my previous comment.

      • Tom that would be very helpful information to know. Especially since co2 rifles are usually considered plinkers. And when you’re plinking you tend to shoot a lot. Or at least I did back in the day.

        By way of explanation, the reason I think the fact you have to wait so long between fills makes the gun a failure is because I can’t see a kid waiting that long to refill and reload with predictable consequences. I’m extrapolating a bit from my own experiences, but I can remember back when I used to plink a lot (back when dinosaurs roamed the earth, ammunition was widely plentiful, and I could actually hit the broad side of a barn), I would regularly shoot 50-100 rounds at a time (usually at least once a week). But I can also remember times when I’d burn through 500 rounds. Granted I didn’t do that often because even then shooting that much was a bit expensive. And granted it took me an hour or two. However I know I did that several times a summer. So I can see a kid who gets one of these as a Christmas/Easter/graduation/birthday/etc.. present taking a bunch of co2 cartridges, a tin of pellets, and deciding to have some fun shooting the entire 500 count tin. And after the first 60 shots or so when power starts dropping off, I can see that kid degassing the remaining co2 from the first charge, trying to unscrew the cap to refill the gun, and when it won’t come off forcing it off tearing the O-rings. Or getting POed that the gun is “broken”. Either way the customer is angry and the gun gets RTMed as broken.

  8. B.B.

    Those really are very impressive groups. If the accuracy holds at 25 yds maybe this rifle should be thought of as a target gun as opposed to a plinker. Given the need to wait so long between CO2 charges that makes the most sense to me. I usually only shoot 5 to 10 targets (10 shot groups) with any one rifle when I target practice anyway. Since this gun gets around 100 shots per fill, that is just right.

    If I were charging $2,000 or more for a 10 meter target gun I would be embarrassed by this rifle at $170. I’m really hopeful this gun shoots less than 1/2″ groups at 25 yards. That will make it perfect to me.

    By the way, I see that Winchester is offering a new (at least to me) CO2 rifle named the MP4 for $170. It’s a pretty cool looking military style rifle. Do you know anything about this gun or do you have any plans to test it?


  9. I have a off topic question about the PA site.

    I just made 2 orders this week and I like to log in to my PA account and check the order status.

    When I checked today I noticed it didn’t have the Tracking Number displayed any more. That was a easy way to check the tracking of the package when I was on my phone while I was on the PA website with out having to access it other ways.

    How come that changed? And can the Tracking Number be included again?

  10. Good-looking groups. My only objection to this rifle would be the same as for my Crosman 1077 which is that it is a pellet and gas hog–mostly because it’s so fun to shoot.


  11. B.B.
    Just read all five parts, By looking down the barrel at any angle you cannot see any deflection, It was the first thing I checked,When I get home today I’ll do a deeper investigation into it. If its bent I’m not sure what I’m going to do. I already got my Hawke sidewinder upgrade coming back, I need new mounts and not sure of what type.
    Anyway thank you for your time If you ever come to Maui check me out I’ll be happy to help you in any of your plans

    • Stan.

      My thoughts were that if you determine the barrel is bent, that series tells you how to straighten the barrel at relatively low cost. The “tool” I made could easily be made and as you saw, I didn’t have to disassemble the rifle. You could fix it yourself.

      The bend, if there is one, is right next to where the barrel enters the base or pivot block.


  12. B.B.
    Thank you, After reading that subject, I knew exactly what you were thinking. When I get home I’ll take a real close look in the particular area that you mentioned. Just really frustrated that’s all

  13. Nice little plug for the disco at the end. The disco is crazy modifiable to be much better than the marauder that everybody seems to want nowadays. I’ve already got my performance on my disco close to maxed out and now it’s getting a repeating bolt, shrouded barrel and double air tube system as well as hand carved thumbhole stock. When I’m done it won’t look anything like the humble disco it started out as. Especially when I get the hydro dip done to shroud and air tubes.

  14. From the photo, it sure looks like the scope ring is slightly left of the centerline of the receiver. I’m guessing thatwith your windage zeroed at 10 yds that the point of impact at 25 yd will shift left.

    Having to wait an hour or more to change carts seems totally unacceptable. I wonder if a standard nitrile rubber o-ring would fix that.

    • Just so your not alone in your analyses. My poor old eyes seen the exact same thing as you. It also looked to me that the bevel on the lower adjustible part was fatter and more blunt to fit the dovetail than on the fixed side. I tightend it tight but I was a little afraid of warping the screw. Upon mounting the scope it shot way low and to the left, I maxed the adjustments all up and to the right which I know your not supposed to do. I’ve almost got a perfect bullseye, dead horizontal but just still a wee bit low. I wrote about it in this blog. And I got great answers but my main problem was that I was only shooting at 15 feet when I was testing it. One idea from a reader was to turn each scope mount 180 degrees around to see if it would reverse my situation? I did exactely that and to my complete shock it shot an almost identical pattern! So the way the mounts looked misaligned to me must have been an optical illusion.

  15. The Xisico XS-60C is the same rifle without the muffler, available in both calibers. It can be modified to shoot 750 fps in both calibers so could be used for short range hunting. The barrels on these rifle need a break in and will produce good groups at distance after being run in.

    PS the Xisico rifles are cheaper than the Umarex model. The higher price may be due to adding the muffler…

    • mii
      I like the gun so far. And it is showing normal characteristics of break-in with a new gun. And I’m sure the groups will get better. And you have to find the right pellet like any other air gun.

      But why design a end cap like that? Especially in this day and age. Most of the guns I see like this the manufacturer is trying to cut cost. And that design I’m sure would cost (more) to produce with all the parts involved. Unless it was already produced in another model. I guess that would be a reason to keep that type of design implemented.

      I guess there is ways to overcome the seal shrinking problem though. Maybe put a warmed wash cloth around the end cap for a bit ? ? ?

      • I’m really liking this gun also! Once this blog and a video helped me understand this crazy valve system. It’ s super quiet and fun to shoot. I had scope problems due to my own stupidity and complicated by me shooting at such a short distance, But out of the box and now with bulk 500 in the plastic package, Crosman wad cutters, I’m getting great super tight groups! I bought the Umarex Octane in .22 at the same time. I’m thinking this gun is potentionately awesome! I fired it into a 2×4 twice and both times it went almost through it! I used a WD40 can straw to measure the distance. It seemed both had deflected in the wood but the distance was easily more than the width. This 2×4 was not pine but I’m not sure what it actually was? It’s definitely a harder wood. The only reason I mention this is because both the Fusion and the Octane have the same sound baffle system I believe. But the reason I only shot the Octane twice is because it can wake the dead it’s so loud! Honestly my ears were ringing for the whole day. I can only hope that after I clean the barrel that it will quiet down a bit? My ultra Liberal anti anything neighbors were already circleing my house wondering what that noise was! Lol

        • Greg
          It sounds like a nice gun so far other than the cap thing. I’m waiting for BB’s 25 yard test before I put the gun on my wish list though.

          And I feel sorry for ya about your neighbors.

  16. I tore up my first O-ring, but am not having any trouble with the second removing it. It may be because I’m now using the recommended oil on the ring. A little wiggle and it pops right out.

  17. The cap may be an idea that Umarex wanted…it’s not needed as far as I am concerned, so what if you have to pop the rifle a few times to get the remaining gas out…o-ring in cap can be replaced with 113, use a duro 70 urethane ….

  18. Gosh, I think I’d be really unhappy with that scope mount for a couple of reasons.

    – The way in which the scope mount clamp is pushed out to the side means it won’t engage well with the groove and
    – the clamp bolt head contacts the clamp only at the bottom meaning an uneven pressure between the bolt and the clamp and risk of being damaged. Really the bolt head should be flush against the clamp all around.

    It very much looks as if it’s got 13mm dovetails or similar and been provided with 11mm mounts- similar to when people try to fit a pistol scope to an HW45 with 11mm mounts.

    • Rich J
      The Monsoon also has 11mm dovetails. And yep the 3/8″ mounts are not the same.

      Try finding scope rings high enough for magazine clearance with a 30 mm tube for the 11mm dovetail to mount a scope on the Monsoon. Hard to do but Beeman makes them. Beeman 5031’s

  19. My fusion wont hold air for more than 36 hours, usually 24. I have replaced the o-ring in the endcap with no change.

    Today i took the endcap off and started to clean it with a SOFT toothbrush and the thread on the cap unwound about 1/4″. i peeled it off, no issue with initial seal. am waiting to see if it holds air longer. was told even a speck of dirt could cause a leak.

    kinda sad that a SOFT toothbrush peeled the threads. If things do not change i plan to get a balloon to put over the cap to see if it is leaking there. if that is not it, i will tear her down and look at the internal seal

    • Sounds like my ex-Mont Blanc Meisterstuck 144…

      The threads where the barrel (fountain pen, folks, not some rare air gun) attached to the section turned into a slinky.

      Hence I no longer possess a Mont Blanc pen. {My current fight is with my most expensive pen — I suspect the ink converter is leaking, leading to ink seeping out the threads between body and section and onto my fingers — not something a new $640 pen should be doing}

        • Fairly recent model, or some years old?

          Conklin, as I recall, is now a subsidiary of YAFA. Whereas my Conklin’s are from 2007 or earlier (my Mark Twain Crescent filler is from 2003, 14K gold nib, Fahrney’s exclusive “Tuscan Brown” — and was probably my most expensive pen at that time, at $329… Yep it was, just sorted the database. The new Platinum Urushi at $636 beats it, but with 10 years between them, a gold nib Crescent may come close…)

            • Fairly recent model – crescent filler. Not a gold nib – either steel or depleted uranium – I can’t remember :). Use it every day for work. Like you I have others but unlike you, I don’t have a database or any record of when I bought them and for how much. My most expensive pen was a gift from the wifey – Big Red. Okay trivia buffs. Who had a “big red” fountain pen (actually it was orange) and what famous treaty was it used to sign and on what battleship (a bit of hint there). Wulfraed, I know you know the answer so let’s give some others a chance.

              Fred DPRoNJ

              • Strangely, I don’t recall… And my reference pen books are 17 miles away.

                Original “Big Red” were, as I recall, orange hard rubber… Parker, I believe. They produced a molded plastic roller ball in the 70s based upon the size/shape. In those days I was mostly Sheaffer (they still make majority “race” even though the fraction is much lower now — Stipula would be second as they made many of the older Levenger pens)

                • Wulfraed, you’re right that “Big Red” refers to a red Parker Duofold fountain pen. What I was waiting for from SOMEONE on this blog was that this was the pen that General Douglas MacArthur had the Japanese sign the Act of Surrender Treaty with on board the USS Missouri in 1945. Sheesh. Am I the only one that stores these useless bits of trivia in my brain?

                  Fred DPRoNJ

  20. Ah! I understand now! You’re talking about the wider part of the scope (the ends) not standing up off of the gun enough… at least that’s what I think you’re saying. I’m going to study your links better.

    I really appreciate the help! 🙂

    • OldPete,

      No, I’m not talking about the scope clearing the rifle. I’m talking about the BOTTOM of the mounts, themselves, hitting the rounded top of the spring tube and the jaw not being able to reach the dovetails on both sides at the same time. Look at the second picture and see howe the BOTTOM of the scope rings is rounded to clear the spring tube.


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