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Education / Training Gamo CF-X gas spring! – Part 2

Gamo CF-X gas spring! – Part 2

by B.B. Pelletier

Part 1

Okay, we’re back with the .22 caliber Gamo CF-X with Air Venturi Ram Air gas spring installed, and today we’re looking at velocity. I discovered that a .22 CF-X is not as powerful as it is in .177. I guess the long transfer port through the rotary breech causes the air pressure to drop off enough that it affects the .22’s velocity, but not the .177’s.

When I tested the .22-caliber rifle with the gas spring, the velocity seemed low to me, so I checked what the same rifle had done with the factory steel spring installed. It was dieseling at that time and the velocity ranged from a low of 574 f.p.s. to a high of 638 f.p.s. with .22-caliber Crosman Premiers. The Gamo rating for this caliber CF-X is 800 f.p.s., so I wondered if anything was wrong.

Just to be extra sure, I asked the tech at Pyramyd AIR to check a second new .22 CF-X with Crosman Premiers. He did that yesterday and the velocity of that rifle ranged from a low of 536 f.p.s. to a high of 618 f.p.s. The average for that rifle is 560 f.p.s. That may seem slow compared to the numbers of the first rifle but remember that all these guns vary a little, and some of them gain speed as they break in.

As you know, the purpose of a gas spring isn’t to boost power, though that sometimes happens. The benefits are longer life, longer cocking without degradation, smoother shooting and a lack of spring torque. You don’t gain any accuracy, though some people do feel that the faster lock time of the gas spring does help tighten groups.

Okay! Let’s test the rifle.

Hobbys first
RWS Hobbys came out the spout at an average of 677 f.p.s., with a range from 661 to 683. The range is a little broad, but the majority were in the 670s. The average velocity calculates to a muzzle energy of 12.11 foot-pounds with this 11.9-grain pellet. Remember that 671 f.p.s. is a “magic” number at which the weight of the pellet in grains equals the foot-pounds of muzzle energy. You can always estimate energy at that velocity, if you know the weight of the projectile in grains.

Premiers next
This is the telling pellet. The two steel spring guns in the same caliber averaged 560 and 615 f.p.s. This gas spring gun, the same one that averaged 615 f.p.s. with Premiers and a steel spring, now averages 628 f.p.s. The range is from 622 to 634, so the spread is much tighter, but the cylinder was cleaned when the gas spring was installed. At that speed, the rifle develops 12.53 foot-pounds at the muzzle.

Air Arms pointed pellet
Air Arms sells a pointed pellet called the Hunter, and it’s made for them by JSB. The weight varies between 15.5 and 15.9 grains, despite the 16-grain weight listed. Velocity ranged from 538 to 587 and I started smelling burnt oil, so I won’t be shooting this one for accuracy.

RWS Superdome
The RWS Superdome is usually a fine domed alternative to Crosman Premiers, but not in the .22 CF-X I tested. Sample pellets ranged in weight from 14.2 to 14.6 grains.The velocity went from a low of 560 to a high of 647. Too much deviation for me, plus the smell of burnt oil grew even heavier.

Cocking effort
The rifle cocks with about 35 lbs. of effort. I don’t have figures for the steel-spring CF-X, but I’m pretty sure this is heavier. As always, the resistance is there from the moment you grab the cocking lever.

So there we have it. It looks like the .22-caliber CF-X is a much different bird than the .177. I’m not sure why this is, but the long transfer port sounds reasonable for now. I would like to ask our readers who now have .177 gas spring CF-Xs if they would give us some numbers to compare, because our steel spring rifle tested at 942 f.p.s. with 7.9-grain Premiers.

For those who want to buy just the gas spring, Pyramyd AIR is working on that right now. The Gamo warranty on the gun will be voided if you do your own work and there may be some other changes. I’ll keep you posted.

Accuracy is next.

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.

52 thoughts on “Gamo CF-X gas spring! – Part 2”

  1. BB, the powerplant in the CFX is identical to what Gamo has been using in their breakbarrels for quite a few years now. Long transfer port or no, there’s no reason for the muzzle energy to be so low.

    Last summer when I tried a .22 CFX I also found (among other problems) low velocity. When I talked to a pyramydair CS rep, he told me that the .22 CFX’s have been problematic – due to QC on these guns, many are coming through shooting slow and they’ve had a high rate of return on them. Mine also had the rotating breach “locktited” shut, btw… it took a hammer to open it the first couple of times (and yes, the rifle was cocked).

    Lastly, .22 CFX owners who are happy with their guns report higher velocities than you’re getting.

    What I’m saying is that CFX you’ve got is probably defective. Some Gamo owners have reported piston seals damaged from the factory, and the CFX has the additional complication of the 2 dynamic seals for the rotating/floating breach. If any of these aren’t sealing correctly, velocity will drop like a rock.

    I suspect that a good internal inpsection and overhaul would bring the energy of that rifle up to snuff.

  2. BB, I seem to remember upper 600’s to a smidgen over 700 with CP’s, which is pretty consistent with what can be gotten from a breakbarrel Gamo or a Quest (which uses an almost identical powerplant).

    My low-mileage .177 CFX only does 870’s with CPL’s, and at times I can spot a wisp of smoke coming from the breach area.

  3. BB,

    What do you mean about the smell of burnt oil (I know it well, but from other contexts)? I’m guessing it’s not good, but is it telling you something about the pellet (e.g., too heavy, too tight/loose, etc.) or the gun? Probably everybody else knows this, so sorry if its a stupid question.

  4. B.B.

    LOL, There were probably thousands of guys (and some ladies) waiting to see part three for the Discovery
    in here this morning like kids on Christmas. We’re all waiting on the tips of our toes for it.


  5. BB,

    this new Discovery rifle has got my interest but also brings up a few important questions. these are mostly about quality. Here in Holland crosman isn’t very well known in airgun circles. Most people buy german made rifles. The only crosman’s we see are the BB guns. There is one pellet gun from crosman that I have seen in real life and that is the 1077. Now i’m not at all happy with the way this thing is built. Very plastic (especialy the trigger group). Overall is seems like something you would find in a toy shop. Now my question is. Is this new discovery rifle anything like that?? Or can we expect greater things?

    greetings from holland

  6. Holland,

    No, the Discovery is much closer to the way a DayState or Falcon is built. Not as shiny, perhaps, and the stock isn’t as full, but the construction of similar. I mentioned all the significant plastic parts in the first report.


  7. Nate/BB,

    I must be missing something. I assumed it was dieseling, but in the report there was an implied connection (or so I thought) to the specific pellets and their suitability (e.g., “Velocity ranged from 538 to 587 and I started smelling burnt oil, so I won’t be shooting this one for accuracy.”) If I smelled burnt oil, I would just assume there was too much in the chamber, not make any conclusions (or trust any results) regarding the pellet. I guess I’m confused about what is the antecedent to “this one” (gun or pellet) in the quote above.

  8. BG_Farmer,

    I really don’t know what to make of it. These two pellets caused the gun to diesel, while the other two didn’t. Whatever the reason, the velocity spread is too large and I probably won’t use either one for accuracy testing.

    I said the compression chamber had been cleaned. So how could the gun diesel? There must have been some kind of fuel present, is all I know.


  9. BB,

    Fair enough. Thanks for your patience…I just thought there might be some less obvious, but well-known correlation b/t burnt oil smell and pellets or powerplant status that I could add to my minimal knowledge of air rifles.

  10. BB,

    This is a bit off topic but I don’t know where else to post or how else to ask you.

    I have a very weird gun:

    I just recently purchased a Umarex CP99. Its really weird as the article number is 412.00.06. I google this and nothing comes up. The usual CP99 is 412.00.00. On the right side of the gun, near the muzzle, there is a pic of a round bb instead of a pic of a flat head pellet usually found in CP99. It comes in a black Walther small case, complete with 4languages manual book, extra back strap and 2 clip magazines. BTW, the clip magazines are black in colour instead of silver.
    I bought the laser for it which fits perfectly. Without the laser, its shooting far to the left even after I have adjusted the rear sight all the way right. (Am I getting a defect?)
    The really weird thing is, on the plastic of the instruction manual, there is a sticker that reads exactly: “Important. This airgun must use with Walther or Gamo 4.5mm Lead BB. To shoot with other ammo. may cause damage to this product.” 4.5mm lead BB? Isn’t this a pellet gun? In the instruction book it is to use pellet. But like I have mentioned, on the side of the gun, there is a pic of a round bb instead of a pellet. What is wrong with my gun?!!
    And I noticed that the power is even less than my plastic 6mm BB gas gun. I know for a fact cuz I shoot magazines and see how many pages it penetrated. And I cant break glass bottles like a nighthawk cp99 I saw on youtube.

    Once again, everything is normal with the gun and what I get in the box except:
    1: Round BB marking near the muzzle instead of a flat heat pellet in other CP99
    2: Product number of 412.00,06 is not anywhere on the Umarex website nor google.
    3: The pellet mags I get are black in colour.

    My serial is J54328082

    Is this a counterfeit? If it is, it is a very realistic one, even the laser fits perfectly etc etc.

    I will be glad to email pics of the gun, the markings, etc etc.

    Thank you very much,

  11. No, Its not.

    I know what a cp99 compact is. Mine is the normal cp with the 8shot rotary mags(except the mags are black). It is a cp99 in every ways(zinc alloy slide, de-cocker on slide, back part of slide can be cocked for single action, etc) except for all those abnormalities I have mentioned in the above post.
    And one more thing I forgot to mention, on the manual there is a red sticker that reads: c02 weapon with under 2 joule power.The manual book is the cp99 manual book. I understand that bb ever tested this gun using 7.9 grain pellets at an average of 355fps. That’s 3joules.

    I can’t find any information anywhere and have emailed Umarex. Is this some sort of toned down version? Where can I post pics? This is really beginning to bug me. There are many series number for cp99, with black one being 412.00.00. mine is 412.00.06. Its not even on http://www.umarex.com

    Any info is appreciated.

  12. Ray,

    You got me! I’ve never heard of this one. If the clip is the usual circular 8-shot one that goes in the middle of the slide when it splits open, I think you have a pellet gun. What the strange number is about I don’t know.

    My guess is that you somehow got a pellet pistol meant for a different market like China, where the muzzle energy is limited to 3 joules or less. But that’s only a guess.


  13. Hi BB,
    I have taken pics and post them on flkr:


    I thought of what you said about it being made for a different market, but there is no such info anywhere..

    And the person who sold it to me had cleverly ripped out a part of the label as you will see in a picture I have posted.

    Please have a look at those pics and give me advice if you can think of any.

    I guess I have to look for lead BB or I might damage the gun?


  14. i understand the benifits of this conversion for hunting. but has the gas spring been tested to stand up to heavy target use like 500 shots a month. or simply put is it as durable as the standard spring. marvin

  15. Ray,

    I’m almost certain you have a pellet pistol intended for China. The sticker about “use only lead BB” is written in Chinese and English, and the English is Chinglesh.

    You have a gun that wasn’t supposed to come to this country, is my guess. You might sell it for a premium to a collector.


  16. Marvin,

    THIS gas spring hasn’t been tested that much, but there are some Theobens that have withstood over 50K shots and still work. Look at the gas spring in your car. They last far longer (duty cycles) than coiled steel, which is why they are used.


  17. In light of our recet gift, the Discovery, has anyone noticed the new Air Hawk,s from Ruger at P.A.?? These 2 guns really smelled like RWS Diana,to me. Shure enough, on closer look,left bottom of box says Umarex USA !! IMPORTANT to note, notice the lack of the RWS scope rail,,dovetails cut direcly in rec.!! COULD IT BE?? W/ stop pin hole we might be onto somthing!! Anyway, with this kind of heritage, at $110 this could prove to be the bargain of the year!!! Any thoughts?? How about you BB.?? Tim.

  18. BB. Thanks so much for clearing that up for me! Now I get it!! The saftey,& trigger look the same? Ill be watching this one. Even w/ some “clunk” it still looks like a good looking gun at a GREAT price. If it comes as close to a Diana 34 as the China copy of the TX 200,,, Ill take 2!! (the new Ruger air hawk) Thanks again BB.! Tim.

  19. BB. Not shure when your leaving,but wishing you & your better half, a SAFE & enjoyable trip to SHOT show! In light of your secret keeping abilitys,& your recent top secret project w/ Cros.,,,, LORD ONLY KNOWS what you will be stirring up at SHOT!!! Time will tell! From all of us out here in airgun land,,Thanks Mr. G.!! Tim.

  20. Anon. Thanks! I agree about the thumbhole version. Im really looking hard at the standard version because of features& price. Looks like a $110 Diana 34 to me,If thats a good copy of a T-5 trigger WOW! (china powerplant can be tuned) Anyway, looks like an exellant entry level gun & an unbeatable price! P.S., Diana, did you see dovetails cut dir. into receiver?? Hmmm. Tim.

  21. Chris,

    The gas spring isn’t a dud. We already know that from the Whisper.

    What we apparently did not know was that .22-caliber CF-Xs are shooting so slow. Re-read today’s post where I describe the pre-testing Pyramyd AIR did.

    I plan to try other rifles with the gas spring this year so we get a well-rounded view of its potential. I am surprised that I have never heard this complaint about the .22 caliber CF-X before, however. Maybe it’s out there, but this is the first I’ve seen of it.


  22. Bg-Farmer, while cruising P.A. today, I checked reviews on Red Ryder. I noted: Quotes: large capacity,classic looks,Very powerfull,adj.sights,Nice wood,,(contractor grade??),deadly accurate,25 yrds,cowboy cocking. My new spring comp. is just looking for a subject! Me & D.Q. will call you later tonight on 3 way, we GOTTA talk! We are thinking for starters shorten brl. akin to Tallon SS,Maccari spring,& Timster GR-9 trig. Of course, just funnin, Red Ryder was around before me & will likely be around long after Im gone!!Bg, we will call you at home later ton. Please dont tell BB., this is our puppy! Timster @ Timster/D.Q. Air.

  23. I often wondered if something like an automotive leakdown tester could be made for an airgun. Perhaps a tool like that could pinpoint significant seal problems in cases like this

  24. b.b. let me re-phrase my statement. I hope the conversion isn’t a dud in a cfx 😉 I did re-read your post regarding slow speeds of CFX in .22, but I also read other reviews recording velocities of mid-to high 600’s with 15-16 grain pellets, while your rifle achieved that with much lighter pellet.
    Wish I had a chrony to check vel. in my cfx.

    I’m not sure if you read all messages in the thread I sent you, but one of the theories was that the gas ram might not be sufficient enough for a .22 pellet. Whether it is correct or not, I can’t tell.

    I hope the techs at PA work the problem out.


  25. Off subject, sorry. To: anyone that owns an RWS. 850 C02-repeater,& wants to customize it in any way,even to the extreme of high pres. air, or would like to just talk “air power”,I found a really acceptible new blog, try http://airnergy.blogspot.com/. This is another “new Discovery” for us out here in air gun land! Certainly cant speak for BB. but I think he would approve! We are all here to exange info & promote our sport! Heart felt thanks to, BB., P.A. & forums like this new one, where we can all exchange info freely!! Tim.

  26. Dragonslayer,

    I was wondering how long it would take you to figure out this simple truth: just massage the Red Ryders’s powerplant to 50+fpe and you have it all AND a leather saddle attachment accessory (which your left-handed younger brother will remove while you’re at school but later deny any knowledge of).

    If you and DQ can just get near 50 fpe out of it, there won’t be any need to worry about shots bouncing off of soda cans or failing to bring down game past 25 yards. Given the ballistics data I have (none) and with the increased velocity, the accuracy should remain deadly well past the current 20 yard limit.

    PS. My list of experiments is getting bigger. I need to go shoot both my RR’s straight up in the air and time how long it takes the BB’s to hit the ground. I think BB should consider adding this procedure to all his product testing, too.

  27. Bg-farmer, You obviously did your homework!! Toooo funny! Your killin me!! A great laugh like this is great,? Or could kill me!Searching for “nitro” tabs! No comeback,Tim!!!

  28. Hi there BB.
    I am happy to know about this gas ram for the Gamo CF-X. Mine is starting to get weak, so replacing the steel spring for one of those might be a good idead. Unfortunately I live in Brazil, so how much I would have to pay in taxes and shipping is anyone’s guess, but when Pyramydair has this gas ram available I will seriously consider buying it.
    Keep up the good work!

  29. Chris,

    The gas spring does fine with bigger calibers. Just look at the .25 caliber Patriot I tested.

    And the gas spring I tested seems to have improved the velocity in the rifle in which it was installed.

    The problem appears to be with the .22-caliber Gamo CF-X.


  30. I have had this gun a little over a week now fired appx 500 pellets. The first 3 shots out of the gun all went through the same hole at 10 yards. Now I am having problems getting shots within 2 inches at that distance. I also noticed the burning oil smell from the beginning, but I though this was normal. I am shooting Crossman Premiers.

    Could the velocity or the dieseling be messing with the accuracy? I ordered the gr3 trigger in hopes of helping with the accuracy, but I am starting to think this rifle has some problems.

  31. Vince,

    For leakdown tester, how about just a tee fitting with pressure guage in center? One side goes to compressor or tank (depending on pressure needed) and other side has pointed (conical) soft gasket for sealing to muzzle; some kind of a vice to hold the rifle and tee might be needed also if tests run over a few seconds. Don’t put pellet in gun, but you could test both cocked and uncocked.

  32. Stabbs,

    Dieseling doesn’t affect accuracy, but detonation does. However, I don’t think that’s your problem.

    Simplify the problem and solve it by adding variables. In other words, if the gun is scoped, take it off and see how it groups. that sort of thing.

    You didn’t mention the caliber of your rifle, but I found the .177 very accurate with light Premiers. Not so with heavies. Next week I’ll try the .22 with Premiers.


  33. BB,

    Well, I feel chastened in relation to my stupid question and inexperience in this particular blog. I also fear that perhaps even my vaunted reading comprehension skills have been questioned. However, the more I think about it, and especially if your pellet testing occurred in the order written, it seems at least least possible that dieseling with the heavier pellets later in the testing cycle is consistent with a defective piston seal or other chamber defect (e.g. scored cylinder walls) allowing lubricant into the recently cleaned chamber, leading to dieseling as well as decreased power output and/or inconsistency. Is this a reasonable conjecture?

  34. BG_Farmer,

    Because I’ve never experienced a rifle doing what the .22 CF-X is doing, I can’t answer your question. A defective piston seal wouldn’t work so well with Premiers, so I don’t think that’s it, but I don’t really know.

    All piston seals allow lube into the compression chamber, according to Cardew, who did the testing (The Airgun From Trigger To Target). So I think the heavier pellets simply held pressure for too long and spiked the temp to ignition. But I don’t know.


  35. BB-
    The problem with my CF-X is definitely the trigger. I am using a .22 caliber with the CP’s. This image is an array of target at which I tried getting groups of 3 at 10 yards in my basement with a 3x scope:

    I ordered the GRIII trigger from CDT and the difference is NIGHT & DAY!!!. This image is again groups of 3, same as above:

    I just fired my 650th pellet through the gun and it seems to be dieseling less. I figure once the gun is properly broken in & I install a better scope, the groups should tighten up a bit. Also, when I installed the new trigger I tightened up all the bolts.

  36. BB,

    Thanks. No arguments, I simply meant “dieseling to the point that it was remarkable to an experienced tester and explicitly noted, apparently as anomalous”. I’m too verbose, as it is.

    Given what I read (and just re-read) in blog and comments, esp. “What is Dieseling–Part 2”, it did seem anomalous that the dieseling was noted with the heavy pellets. I think the higher initial back-pressure of the heavier pellets could exacerbate a piston seal defect, leading to less total pressure and more available oxygen.

    Anyway, I will shut up…although I will keep hoping to read about what is found out after tearing into the CF-X’s, if that happens. I do know I won’t miss the Gamo forums (went to do a little research) — not much uplifting there except a bittersweet reminiscence of Brecht (“sehr riechende Tiere”) compliments of some participants.

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