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Education / Training Gamo Swarm Fusion 10X Gen II air rifle: Part 4

Gamo Swarm Fusion 10X Gen II air rifle: Part 4

by Tom Gaylord
Writing as B.B. Pelletier

Part 1
Part 2
Part 3

This report covers:

  • The test
  • Sight in
  • Falcon group
  • Discussion
  • RWS R10 Match Pistol pellets
  • Discussion 2
  • JSB Exact RS dome
  • Discussion 3
  • Second group of JSB Exact RS
  • Third group of JSB Exact RS
  • Summary

Today I mount the 3-9X40 Gamo scope and shoot the Fusion 10X from 25 yards. It will be an interesting test.

Mounting the scope

The scope that’s bundled with the rifle comes with a one-piece mount already attached. All you have to do is loosen the three Torx screw on the scope mount base with the wrench provided and clamp the mount to the 11mm dovetail base on the rifle. The mount has a scope stop pin that fits into the rear hole in the base and locks the mount from moving under recoil. I had the scope on and ready to go in 10 minutes.

The test

I shot off a rest at 25 yards. I used pellets that showed potential in Part 3’s test with open sights, except I had run out of H&N Match Green pellets, so I substituted something else.

I shot with a modified artillery hold, since I learned in Part 3 that the rifle likes that best. I actually modified my hold as the test progressed and I will tell you about it as we go. Let’s get started!

Sight in

I sighted in from 12 feet with Air Arms Falcon pellets. The first shot hit the paper at my aim point, which means it will climb higher as I move back, so I backed up to 10 meters and fired a second shot. Shot two was higher and also to the left. It was close enough to the aim point that I backed up to 25 yards to refine the sight picture. It took a couple more shots to get the rifle shooting where I wanted and then I fired the first group. While most of my groups today will be 10 shots, this first one was only 5 because I was also testing whether loading single pellets or loading all 10 into the magazine worked best.

I’m not going to show the first 5-shot group because it overlapped a couple sighters and isn’t easy to see. But now I loaded the magazine with 10 of the same Falcon pellets and shot a group.

Falcon group

The ten-shot group of Falcons was revealing! It was looking to be a good group until the final four  shots. The group grew from 0.475-inches between centers to 1.554-inches. 

Falcon group
Ten Falcon pellets went into 1.554-inches at 25 yards. The first 6 of them are in 0.475-inches.

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Before we move on I need to tell you what I think is happening. First, I believe the hold is the most essential part of accuracy with the Fusion 10X. Unfortunately it has a thumbhole stock that cannot be held as loosely as I would like, but a loose artillery hold is a key to the rifle’s accuracy.

Next, I don’t think there is a large difference between loading pellets one at a time and loading the entire 10-shot magazine. And the way the Fusion 10X works, using the magazine is certainly easier. I finished the test shooting from the magazine.

The scope is reasonably clear at 25 yards. I adjusted the eyepiece until the crosshairs were sharp through my everyday glasses, and I could see them on top of the 25-yard bullseyes.

For a bundled scope this one isn’t bad. And the fact that it comes with the mount already installed on the scope is a plus for those who don’t like mounting their own optics.

Finally, I don’t believe that Falcon pellets are necessarily the best in this rifle. I will try some other types. I did not adjust the scope after this group.

RWS R10 Match Pistol pellets

Next to be tried were ten RWS R10 Match Pistol pellets. These landed low and left of the bull. The group measures 1.397-inches between centers and once more there is a tighter cluster of five in the center of the group. There were not shot in succession, but for each of them I was extra-careful to hold the rifle lightly. Now I am learning something!

R10 group
Ten RWS R10 Match Pistol pellets went into 1.397-inches at 25 yards. The aim point was the bullseye at the upper right.

Discussion 2

Okay, I think I have it figured out. The Gamo Fusion 10X is very sensitive to how it is held. It is also pretty accurate, but only when the hold is right. The pellet probably does not make as much difference as it will appear in this test, but I did move on to the JSB Exact RS dome.

I also believe that feeding pellets from the magazine does not detract from the accuracy. Maybe I’m talking ahead of my test results now, so let’s move on and I will show you.

JSB Exact RS dome

I had left the scope adjusted where it was after my first 5-shot group and both the second and third 10-shot groups and now I could see the Fusion 10X was shooting too low and left. So I adjusted it 5 clicks up and two to the right. Ooops! Should have waited to shoot the JSB Exact RS domed pellets first. Because the 10 JSB pellets landed to the right of the bull. The elevation seemed correct but the windage was off to the right.

Ten JSB Exact RS pellets went into 1.046-inches — BUT only the first three shots are high and horizontal. I then slid my off hand out to the end of the cocking slot and shot the next 7 shots into a group that measures 0.648-inches between centers. For 25 yards that’s not that bad! In fact this group was so impressive to me that I drew a circle around the last 7 shots, to separate them from the first three shots.

RS group 1
The first group of 10 JSB Exact RS pellets went into 1.046-inches between centers. The final 7 shots that I really concentrated on are in 0.648-inches, which is inside the circle.

Discussion 3

You must be wondering why I couldn’t REALLY concentrate on the first three shots, if I knew what was happening. Let me explain. When you shoot with the artillery hold there is a final step that is sometimes critical, and other times not. Before you squeeze off the shot you close your eyes and relax, then open your eyes and see where the crosshairs are. If they have moved from where you want to hit, you make small adjustments of your hands and elbows and then do it again. You keep doing it until the crosshairs are still on target after you open your eyes. Then you take the shot.  This takes time and a LOT of concentration, but as you shoot a rifle more and more, it starts to become second nature.

It takes a lot of concentration for every shot, but I can do it when I have to. And with this rifle it seems necessary.

Second group of JSB Exact RS

JSB Exact RS pellets seemed like a good pellet to test, so I adjusted the scope three clicks to the right and two clicks up and shot a second 10-shot group. I did my very best this time and 10 JSB Exact RS pellets went into 0.959-inches at 25 yards. That’s not enough different from the last group to say much of anything.

RS group 2
The Fusion 10X put 10 JSB Exact RS pellets into 0.959-inches at 25 yards. This group is a little more to the left and a little higher, but not much!

That was the best I could do. But my conscience still argued that I should have done better. I was tired but still functional, so I shot one final group. This time it was just five shots. I figured I could hold it together that long. I adjusted the scope up two clicks and right three clicks.

Third group of JSB Exact RS

This time I pulled out all the stops on each shot. And it worked! I was able to put five pellets into a group that measures 0.495-inches at 25 yards. To tell the truth I wanted to shoot a second five shots, but I was concerned I wouldn’t have anything to show you. Other airgunners shoot five shot groups as a matter of course, so there you are!

RS group 3
The Fusion 10X put five RS pellets into 0.495-inches at 25 yards.


The Gamo Swarm Fusion 10X GenII repeating pellet rifle is a remarkable airgun. It is smooth, accurate and has a reasonably nice trigger. Its GenII 10-shot magazine lies flat for a low profile, yet the rifle feeds very reliably. It’s easy to load and even easy to fire single-shot without removing the magazine.

This gas spring-powered breakbarrel rifle is easy to cock. It’s not a mega-magnum by any stretch, but it’s a good honest .177 that develops almost 15 foot-pounds. Yet I can cock it easily with one hand.

The rifle is lightweight, yet does not vibrate or recoil very much when it fires. And all of this comes to you with a scope for under $300. Gamo has done very well with this one.

author avatar
Tom Gaylord (B.B. Pelletier)
Tom Gaylord, also known as B.B. Pelletier, provides expert insights to airgunners all over the world on behalf of Pyramyd AIR. He has earned the title The Godfather of Airguns™ for his contributions to the industry, spending many years with AirForce Airguns and starting magazines dedicated to the sport such as Airgun Illustrated.

38 thoughts on “Gamo Swarm Fusion 10X Gen II air rifle: Part 4”

  1. B.B.

    From the way you described how you shot this rifle I cannot imagine you finishing the 25 yards test using the various pellets in under 2 hours. I can only imagine how very taxing it would be until it becomes second nature to the owner. Probably would take at least 2 tins worth.


  2. BB,

    Unless I am missing something,… you started (shot) at 25 yards,… but you refer to 10 meters off and on throughout the report.

    Glad you got it to shoot that well at 25 yards.


  3. BB,

    Gamo must have come a long way on their triggers for you to say the C.A.T. trigger is decent. I remember the one on my CFX (shudder). Thank goodness for Charlie Da Tuna. Now if they could just figure out how to deal with that hold sensitivity without adding weight.

    After you shot the R10 Match pellets you adjusted up and to the right. Oops, too far. Then you state that you adjusted it two more times to the right to bring it closer to the target. Should they not say left?

    Maybe that shooting session took more out of you than you thought. 😉

    P.S. I am not a fan of the thumbhole stocks or pistol grips. They are fine for quick, close in shots, but as you point out they can be a bit of a hinderance for very precise shooting. When I was shooting firearms at long ranges I had learned to hold the rifle loosely, touching it as lightly as possible. My mind was focused on the target so I never really felt the recoil anyway.

    • RR,

      When I said decent I struggled to come up with a good word. The CAT certainly has no discernable second stage stop, but it’s so light that I can tolerate it and even get used to it. That’s what I meant by the word decent.


      • BB,

        I understand, but I am glad that you took your explanation further so others would understand. I keep hoping that one day they will figure out how to make a decent trigger, but I am not holding my breath.

  4. I haven’t shot mine for the last two months, but my notes say that mine like being pulled “snug but not tight” into my shoulder. I believe you said the Sig ASP liked that kind of hold, so I’ve added trying that to my arsenal of things to try when I get new airguns. My Gamo Whisper Fusion also seemed to prefer that hold. Just food for thought, if you ever have reason to get around that gun again.

    • NewToOldGuns

      My Stoeger ATAC does well at 25 yards using H&N Field Target Trophy pellets 5.5 mm. It demands to be very firmly pulled into my shoulder by my left hand gripping the end of forend. It consistently groups 10 shots under 1″. Any change from this hold or pellet selection causes accuracy to suffer. I do weed out any pellets that measure less than 5.54 mm using a Pelletgage. This hold is not useful for my other springers. I do suggest to anyone struggling to find a best hold to try it. It also helps overcome triggers that are too hard to pull smoothly.


      • Hi Deck

        Thanks for the advice!

        Almost all my shooting is standing and open sight these days, and I find many guns like when I shoot out of the web of my off hand, between my thumb and forefinger, just ahead of the trigger guard, with my palm facing away. That lets me get my elbow into my hip for stability, and also “free floats” the rest of the gun. I thought I was just weird, till I saw Gunny using the same hold shooting an old lever rifle. So, okay, I’m weird, but not alone on that hold 😉 .

        • NTOG

          I like your off hand position. It adds stability like holding binoculars. Have never tried it unless In my squirrel hunting days many years ago. All my rifle work is seated from a bench except when blasting away for the thrill of it with a semi auto at a rifle range.


  5. B.B.,

    Many thanks for this update! I’ve been looking forward to seeing it!

    It has clarified something that’s been at the back of my mind—the rifle is very hold sensitive. I typically have a difficult time getting any kind of cheek weld; a lower jaw weld is what it seems to wind up being. Any suggestions or advice please?

    I did try sliding my off hand all the way up the stock to the cocking mechanism, by that did get tiring. I’ll try it again paying more attention to the results. My current best hold is right where there is a gap in the checkering.

    Some questions, if I may please?

    Could you describe the trigger hand hold a little bit more?

    How firmly do you hold this rifle into the shoulder?

    The second stage is maximally adjusted at the factory; did you notice any changes adjusting the first stage? (I adjusted it and it seems like it made it nicer and shorter.)

    Many thanks,

    • AP,

      Well, the AirForce rifles give the biggest problem with getting a cheek weld and the solution is to put the toe of the butt into the hollow at the top of your shoulder. The Fusion 10X stock drops more than an AirForce butt, so I think all you need to do is just move the butt an inch or so higher on your shoulder. I have to do it so often that I forget to mention it. I don’t remember if I did it with the Fusion, but if I did, it worked.


      • AP,

        You need to watch the artillery hold video here:


        I forgot to address how firmly I pull the butt into my shoulder. Not firmly at all. As lightly as that thumbhole stock allows. As for the trigger I addressed that in Part three. The answer is the trigger did not change at all.


    • Mister AP,

      Here’s another good video on the Gamo Swarm Fusion Gen II that shows a hold that works. Spoiler Alert: If your’s is in .22 caliber you may want to try some H & N FTT (Field Target Trophy) pellets with the 5.55 head size. You may also want to ditch the scope that came packaged with the gun.


  6. B.B.,
    That’s some nice shooting on that third group with the JSB RS pellets, and I can’t say I’m surprised. I bought a 4 pack (buy 3, get one free) of these from PA:
    And I got them because they proved to be the most accurate pellet in every .177 caliber pistol I have.
    Also, I use JSB domes in my .20 caliber Sheridan…and JSB RS .22s in my HW30…it seems a disproportionate number of my airguns shoot their best with JSBs…I guess those guys know their stuff! =>
    Take care & wishing continued good health to you and to all who read this blog,

    • TWO unrelated issues: 1) For a 5 meter range (and others) WHAT is the “start” of the distance? Lead foot? Muzzle?? 2) Now prepping to replace a broken mainspring on my ~9 yr old Remington Summit rifle: opened up now it looks like it has ~3.8″ of pre-load!!!! THAT can’t be true, for such a stiff spring!! I’ve serviced magnum airguns before, but this STIFF spring with 3.8″ pre seems VERY high!!!!!! ALL help greatly appreciated! —Barrika the LURKER (sees EVERY day’s postings!)

      • Barrika the LURKER,

        At a range the distance is measured from the target side of the red or orange line on the floor to the target (s) Some ranges have optical barriers that will trigger alarms if they are penetrated. In competition the rules will spell out what if anything may or may not cross beyond the front (target side) of the line. Some ranges and rules REQUIRE that a foot be ON the line all the way to the downrange side but no farther! Seems that some Judges love those kind of convoluted rules!
        If this is your personal range well You Make The RULES!


        • Barrika, I see that Shootski has already given you the more complete answer; but if your question was in reference to my crude drawing, the stick man should actually be back all the way in the corner, and the 5 meters is from the face of the target to the toe of his front foot…hope that helps. =>

      • Barrika,

        Since the stroke volume is what really determines the power I would probably chop the spring leaving only an inch of preload. You will most likely end up with the same power and less effort in compression.


  7. “LURKER”,…. 😉

    I would bet you could chop a bunch off that and not drop any fps. Me? I would chop (progressively), find the “sweet spot” and then get a replacement with the same wire diameter and twist rate,.. and new length. That way you got some nice, flat proper ends. Or,… just cut and go as is. But,… that is just me.


    • Well, Chris… The new spring (from OEM vendor, Crosmann) is about 0.8″ longer than the old failed one. I say ABOUT because the old one failed into FIVE pieces, making exact length a little iffy. Same number of coils though, and same wire gauge and same coil OD. But since it IS Crosmann, I’d have thought they’d not supply me with a spring that long. I will call & talk to them about it. And chopping progressively sounds like a LOT of work, rebuilding the guts every time. As far as just cutting and going as is: those formed flat spring ends have to help a LOT, don’t they? I’d not get that on a chop and go installation (at least on ONE end).

      A funny point about this: the rifle COULD cock & fire erratically, with the failed spring, but when removed, one section of it was interweaving into another: net MINUS 0.4″ pre-load! 🙂

      • Barrika,

        Well, that is certainly interesting. Yes, it would be a lot of work. I trust that you have a tool/jig to compress the spring during assy. and disassembly??? You will need it. This place does springs. I have used their tune kits and even spoke with them on the phone. They have just plain springs too. Maybe give them a call or email them and they could give you some insight.


        The flat ends allow for spring twist and rotation. You can do a flat type cut with a Dremel tool or something, but it will not be near the same. It it truly 3.8″ preload, I would bet you could lose 3″ with no fps drop.

        Was it hard to shoot (vibration, slap, etc.) ? Not very accurate? Could you get 1″ groups at 25 yards?

        Keep us posted,…… Chris

  8. a) The best I’ve done in the past with this one is 0.9″ five-grps at 50 ft (my std range for pellets)
    b) It was not excessively noisey to cock or shoot before, but then not the quietest either.
    c) Of course I have a spring compressor rig to svc the power plant. TWO: one for woosy guns, one for magnums.
    d) I agree that cutting the spring CAN be done, but I’d not get the LARGE, SMOOTH end that factory springs have, even after using my dremel on it. I’ve yet to call Crosmann (mfr) (today) and ask them What The Heck??
    e) As I said before, the new spring has the same number of coils, same wire guage, & OD, but far longer than the one that failed (after reassembling all five pieces).
    f) Re-stating the obvious: that is WAY TOO MUCH PRE-LOAD FOR A HEAVY SPRING (even with a compressor)! Don’t YOU agree, BB??

  9. OK guys: mea culpa! It turns out that while I was SURE that I had inserted the spring FULLY into the piston, it hung up REPEATEDLY, even with twisting and light hammering. But I KNEW it should not be THAT grossly lpng, so before I called Crsmn, I took ALL the guts out of the rifle, and sure enough: the spring CAN go into the piston (OF COURSE!), then it measures with 1.5″ pre-load. Not easy to install, but I’m getting there. The 1/2-flat end cap is giving me some grief, but I’m sure I’ll make it now. Lesson learned: TAKE THE PISTON OUT, to get the spring inserted. Besides, the piston needed to be cleaned and re-lubed anyway. —feeling STEWpihd, Barr…

  10. Mea not QUITE so CULPA!!! I FINALLY got this Rem. Summit to WORK today! I might go out & buy a few Lottery Tickets, I’m so lucky. Bottom line is, Crosman was a LITTLE helpful, in that they confirmed that I bought & installed the right spring, but “NO WORKIE”! Beyond that though, they said I could visit a “local” repair shop that was Crosman certified. I called them: no go: closed for Covid, but he DID talk to me, and he mentioned a few glitches on this minimally-produced rifle. ONE of which is that some of the replacement springs are sold TOO LONG. MINE included, apparenlty… I came up with the idea of cutting off a wee bit of the “back spring guide” (think of it as a washer on steroids, 1.342″ long OEM. I cut off 0.14″ of it, smoothed it, polished it, and found that I could now BARELY compress this spring BY HAND, with another pair of hands to insert the “fixed pin” that holds the spring in. AND… drum-roll please, THE GUN WORKS! The too-long spring WAS preventing the sear from latching up! I’ve got my Remy back!!!! Thinking of going out & getting drunk to celebrate, oh, wait: can’t do THAT thanks to Covid. Still, it’s a good day! It might loose a few fps, or not: I’ll test it as soon as my Chrony is repaired (( Chronies apparently die of old age far too soon, per their factory…))

    • Barrika,

      So,…. the spring was at full bind (compression)… not allowing the sear to latch up?

      Good for you getting it fixed. Egg on face 🙁 for Crosman.


    • Barrika,

      I will add,…….. if that spring is now at 99% full compression when cocked,… then there is good chance that a shorter spring (or smaller wire, etc.) would yield the same fps and also a smoother shot cycle.

      It is too bad that you had to go through all of that trouble.


    • Barrika,

      Congratulations and a job well done. I agree with Chris. I don’t think you will lose power because it is not the strength of the spring that determines the power but the stroke volume of the airgun. You will find it easier to cock and probably less vibration especially if you put a little Tune In A Tube on the spring to further dampen vibrations.


  11. The Tune-in-Tube was applied on the rebuild! I am not as dumb as I look! 🙂
    I will start break-in shooting for this rifle tomorrow, but of the first three test shots in my basement (a VERY rugged bullet catcher, desgined by BB!) the first tow were quite loud (detonation!), then less worse 3rd round as the lube settled down. I’m hoping for better accuracy, but at least it WORKS!

    • Barrika,

      Heavy weight pellets will keep the detonation incidence down while you are breaking it in. That was mighty smart putting in the TIAT during assembly rather than depending on it being spread as you use the airgun.


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