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Education / Training Crosman 2400KT CO2 Air Rifle — Part 14

Crosman 2400KT CO2 Air Rifle — Part 14

by Tom Gaylord
Writing as B.B. Pelletier

This is Part 14 of the Hiveseeker guest blog on the Crosman 2400KT. Today is titled Modding the Crosman 2400 family — Primer 3.

This is the most popular guest blog series we have ever published. Hiveseeker says it is the last in the series, but I think it might not be. You readers will help him decide.

If you’d like to write a guest post for this blog, please email me. Now, over to you, Hiveseeker.

Crosman 2400KT CO2 Air Rifle – Part 14
Modding the Crosman 2400 family — Primer 3
By Hiveseeker

Part 1
Part 2
Part 3
Part 4
Part 5
Part 6
Part 7
Part 8
Part 9
Part 10
Part 11
Part 12
Part 13

2400KT cover photo
The 2400KT CO2 Air Rifle that I modded for this report is only available directly from the Crosman Custom Shop. It is shown here disassembled with a mix of stock and modded parts. For scale, the background grid on all photos is one inch square.

WARNING: These modifications can change the operation of a gun in ways it was not designed for. Non-factory or modified parts can fail, especially if subjected to higher pressures than originally intended. Pyramyd AIR advises against making such modifications or conversions. This report is for information, only.

This report covers:

The mods (continued):

  • (5) Extended or hollow bolt probe
  • (6) Barrel
  • (7) Trigger
  • (8) Sound moderator
  • (9) Grips and stocks
  • (10) Conversion to air
  • Conclusion

In Part 12 we provided an introduction to modding the Crosman Crosman 2240 family of CO2 guns, and in Part 13 covered several of those mods which we will be concluding today. I’ve ranked the difficulty of these mods from easiest (*) to hardest (*****). All velocity testing was completed with 14.3 grain Benjamin Discovery Hollow Points.

2400KT bolt
Here are the Extended Hollow Probe from GMAC Custom Parts (top) and stock Crosman bolt shaft (bottom). Inset shows both the added length of the extended probe, and the hollow opening that facilitates CO2 flow.

(5) Extended or hollow bolt probe

Difficulty ***
Cost: $15-$35
An extended bolt probe (bolt tip) is supposed to increase accuracy by deep-seating the pellet further into the barrel rifling than the standard bolt. This can also increase velocity by pushing a pellet completely past the transfer port hole in the barrel, allowing the CO2 free flow behind the pellet skirt.

A hollow probe maximizes CO2 flow past the bolt by lining up an opening in the hollow bolt tip with the transfer port hole in the barrel, allowing CO2 to actually flow freely through the bolt itself. Other probes provide a similar advantage via a very narrow bolt tip that facilitates unobstructed CO2 flow into the barrel. This is another free lunch mod with no cost, outside of dollars!

On fellow reader Kevan’s recommendation, I purchased a bolt that incorporates both these upgrades, the Extended Hollow Probe from GMAC Custom Parts in the UK. Kevan reports a 14 f.p.s. velocity increase and improved accuracy with this mod. Unfortunately my 2400KT took a major cold-weather hit by the time I was ready to test this bolt, which was actually the last mod I completed. All other testing had been at temperatures of 84 to 88 degrees F, but the highest I could muster for this test was 76 to 78 degrees F due to cold weather. My average velocity plummeted from 525 f.p.s. to a new baseline of 457 f.p.s., a drop of 68 f.p.s.! When I retested with the new bolt I was pleasantly surprised with an average velocity of 481 f.p.s — a 24 f.p.s. increase. I noticed that the report seemed slightly louder with the mod, which makes sense since CO2 flow was obviously increased. The bolt fit is quite tight, though it smoothed out a little during testing. There is exactly enough room for loading the Benjamin Discovery Hollow Points. Longer pellets can be fit nose-first into the breech past the extended bolt, though loading definitely requires more attention and finesse now.

For evaluating accuracy with the extended bolt, I felt that repeating my 20-yard accuracy test from Part 9 would be the most revealing. Out of 5 pellets, however, only 2 shot smaller groups with the extended bolt. I would call my results inconclusive, but a couple interesting points to note about the extended bolt are that those groups averaged slightly smaller, and while none of those groups were especially tight all except one were very consistently in the half-inch range which is not bad. The accuracy improvement afforded by the extended bolt might depend on the pellet.

2400KT bolt table
Accuracy results at 20 yards with the Crosman bolt and the Extended Hollow Probe from GMAC Custom Parts. Smaller groups are shaded in green.

Pro tip: This mod is more work than it initially appears. You will need to remove the steel breech in order clear the hammer pin so that you can slide the bolt shaft (minus bolt handle) into the steel breech. There was exactly enough room for the extended bolt between the hammer pin and breech screw for reassembly. If you are installing a hollow probe, make sure that the opening in the hollow bolt tip is down toward the valve opening instead of up when you install the bolt handle.

2400KT barrel
Velocity increases with barrel length for a CO2 gun. If you are after maximum speed, go with the longest barrel practical for you.

(6) Barrel

Difficulty **
Cost: $15-$65
Most of what you need to know about barrels was covered in Part 10 and Part 11 of this blog. For a CO2 gun, velocity increases with barrel length. We found that by changing the barrel from 7.5 inches to 24 inches velocity could be increased up to 153 f.p.s. with no other modifications. All of these Crosman CO2 barrels are interchangeable, and it’s being reported that the 26.25 inch Benjamin Maximus barrel is also compatible.

Pro tip: Remember what we mentioned under valves — if you want a Lothar Walther barrel, order it with your Custom Shop gun even though that means you will not get a Crosman power valve. After your purchase, a commercial power valve will be easier to find than a Lothar Walther barrel.

Let me mention here that having put a lot of pellets through almost a half dozen different 2400KTs and even more barrels, several emerged as consistently accurate across the board in both .177 and .22. These were the boxed Crosman Premier (though sadly no longer available in .22), the Air Arms Falcon, and the RWS Hobby. Others worth trying include all the JSB pellets such as the JSB Diabolo Exact Jmbo, and the H&N Field Target Trophy which is available in different head sizes. Based on my success with the Air Arms Falcons I just recently tried two new pellets in this gun with excellent results, the Air Arms Diabolo Field and Air Arms Diabolo FieldHeavy.

2400KT pellets
My Lothar Walther 14.6 inch barrel just loves Air Arms pellets! Left to right are groups from the Air Arms Falcon (10 yards), Air Arms Diabolo Field (10 yards), and Air Arms Diabolo Field Heavy (20 yards).

2400KT trigger
Yes — the 2400KT comes with an adjustable trigger, hidden away under the pistol grip!

(7) Trigger

Difficulty ***
Cost: $10-$100
I did not modify the trigger because I found the stock trigger to be quite acceptable. While not documented anywhere in the Custom Shop website or owner’s manual, the 2400KT has an adjustable trigger as you can see above; Part 2 provides details and adjustment suggestions. I also recommend the trigger shoe in the Crosman Custom Shop, which reduces the perceived trigger pull. Mods range from deburred and polished trigger and sear replacements for $10-$20 (or you can do your own polishing), to full 2-stage adjustable trigger kits for $100.

2400KT muzzle brake
The black and silver Crosman muzzle brakes are ported, while the brass is not.

(8) Muzzle Brake

Difficulty *
Cost: $15+
The ported Crosman muzzle brakes in the Custom Shop do seem to reduce the volume of the discharge slightly, though I did not have a decibel meter to confirm this. Other than that, they primarily add bling and muzzle protection to your Custom Shop purchase. There are also third party sound moderators available, and I’m going to mention them briefly only because they are so widely available. They work but be aware that the legality of a removable moderator is not clear and I cannot recommend them.

2400KT grips
Although the most economical Custom Shop grips and shoulder stock are shown here, a wide range of grips and stocks are available within the Shop and from third party sellers.

(9) Grips and stocks

Difficulty *
Cost: $3-$60+
The Crosman Custom Shop offers a wide variety of grips and stocks, from standard black 2240 pistol grips for the 2300KT at only $2.95 to zebrawood target grips for $59.94 — the price of a 2240 itself! There are also dozens of shops and vendors offering all sorts of custom grips and stocks, including adapters that will let you install military folding stocks like the UTG PRO 6-Position Mil-Spec Stock Assembly.

Pro tip: A common complaint is how low the Crosman shoulder stock is. Many shooters add a section of pipe insulation or other padding for a custom cheekpiece riser.

2400KT air
Conversion to air is the most powerful mod you can make, but was one that I did not attempt.

(10) Conversion to high pressure air or HPA

Difficulty *****
Cost: $75-$95+
This section will be brief because I did not perform this modification myself. Instead, I will refer you to B.B.’s Crosman 2240 Conversion to Air where he achieved velocities surpassing any of the mods I’ve presented to you here. The PowerMax HiPAC that B.B. used in that blog continues to be one of the easiest and most popular kits available. Difficulty is moderate if you are only filling to 1,800 PSI. However, higher fill pressures up to 3,000 PSI require reinforcing the valve and stronger seals. A diverse array of other HPA mods with various fill tanks or bottles are also available.


As you can see, excluding a conversion to air, if you order a 2400KT that includes a long barrel and the Crosman power valve your gun will arrive mostly pre-modded! Crosman really knows its hardware, and they are squeezing some amazing performance from that little CO2 cartridge. Other shooters report that all of these mods will work on some guns, including the power adjuster and max flow transfer port from which I saw no velocity gains. Despite a couple of unsuccessful mods, I still felt that I’d learned a lot. I hope that this blog has provided some helpful information, whether you are simply curious about the subject or are actually ready to take the plunge into modding!

I was browsing a popular modding site and came across a photo of a highly modified 2240. It was so tricked out I wasn’t sure if any of the original gun was left in there! “Wouldn’t it have been cheaper to just buy a Marauder Pistol?” I asked. The response was “That’s not the point!” And for some, it’s not. The process of customizing a gun to make it more powerful or better suited for your own purposes can be just as important as the end product. Others — a bit more like me — may be quite content to just buy that Marauder pistol outright. And that’s okay, too!

A last word on the 2400KT
Interestingly, when I first read B.B.’s 2240 Conversion to Air I realized that my search for a gun like the one he created — but without the need for modding — was what had originally led me to the 2400KT. As I write these words about modding that gun, I feel that this now brings this entire blog series on the Crosman 2400KT CO2 Air Rifle full circle.

The face of airgunning has changed dramatically since B.B. posted my first blog on the 2400KT back in 2014. Until just recently, I considered this gun to be a poor man’s PCP. But I have now seen an entry level PCP on sale for less than a 2400KT! Obviously, many modders will rather start with a gun that’s a PCP straight out of the box like the Benjamin Wildfire or Beeman QB Chief, rather than going to the trouble of converting a Crosman CO2 gun. We are truly living in the Golden Age of Airgunning, and whether you want to use a stock product off the shelf or customize a gun with your own two hands, the options are getting better all the time!

Finally, during this blog series we’ve thrown a lot of numbers and technical information around, but I want to wrap up by reminding you that the most important factor is one you can’t put a number on. Are you having fun? In the midst of all these recent changes, I see the Crosman 2400KT CO2 Air Rifle upholding its role as a fairly powerful, accurate gun that is very simple to shoot with no pumping or filling. Yes, I am having fun! And, if I’ve helped any of you have a bit more fun and appreciation for this gun, then B.B. and I have accomplished our goal.

I’d like to wrap up this series — which ran much longer than any of us expected — by thanking B.B. first and foremost for letting me write it, and for his time and patience in posting it. It has been my privilege and my pleasure to work with him. I’d also like to thank a very encouraging and supportive community here at the Pyramyd Airgun Blog, from whom I have learned more than I have taught. Finally, I would like to thank the folks at Crosman, both for so many fine products — especially the totally unique Custom Shop — and for their patient Customer Service team.

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.

75 thoughts on “Crosman 2400KT CO2 Air Rifle — Part 14”

  1. Hiveseeker,

    Congratulations on an excellent post! Although I think there is still something in the back of my head telling me that the story is not yet finished.


        • Hi Gunpug,

          Welcome to the blog, and sorry it took me a few days to respond. I didn’t shoot any groups with most of the barrels in the barrel length test — I was only testing velocity at that point. All of the Crosman barrels, including the 24 inch, reportedly have good to excellent accuracy. The 14 inch Lothar Walther barrel on this particular gun was quite accurate (as you could see in the part on barrels here, and also at /blog/2017/10/crosman-2400kt-co2-air-rifle-part-9/). My only added comment is that I noticed that the end of the 24 inch barrel vibrated with each shot, though I read nothing elsewhere suggesting this might have a negative impact on anything including accuracy.

  2. Hiveseeker
    Maybe this is the part that ain’t finished yet.

    I’m glad you finally put a picture in this report about the custom shop trigger your gun has. Now here is a picture of the Marauder pistol and 1720T trigger assembly and parts.

    I think you will clearly see the difference. And see why the there is a difference in performance of the two trigger componants.

    And again what is nice about the Crosman engineering. Is that you can get part numbers from the Marauder pistol drawing and order parts from Crosman. They drop right in your custom shop trigger assembly.

    Here is the picture.

    • Gunfun1,

      EXCELLENT, and thank you again. So THAT’S what that unused pivot hole in the frame is for! These guns are easy to mod thanks to flexibility and interchangeability built around a common frame design and many commonly shared parts. This is a good line of products, and you really have to admire Crosman’s efficiency and engineering.

      • Hiveseeker
        And no problem. I just wanted to make sure it was seen how easy it is to interchange parts even in the trigger assembly.

        And I should note also that the Marauder pistol trigger parts will of course work in other guns that use this trigger grip. Like the obvious 2240. But also even the 1322/77 pistols as well as the 2300 series.

        If you already have one of the types of guns I mentioned it’s just a phone call away from Crosman. And like Hiveseeker said. He likes the trigger as is on his custom shop gun. And I can say I like a the factory out the box trigger assembly on the 2240’s and guns mentioned. But it is nice to know that the upgrade to a true 2 stage trigger is easily available.

    • HiveSeeker and Gunfun1, I’ll second that opinion on using the Marauder Pistol trigger group. I shoot Air Pistol Silhouette, but I’m a cheap so-and-so. I started out with a Daisy 717 single-pump pneumatic, and pretty much fell in love with the sport. When the Daisy proved out to not have enough power to reliably knock down the Ram target, I started looking for a (cheap) replacement. I found the 2240 and was quite happy with it.

      My scores improved, but I wasn’t able to maintain enough trigger control to improve as much as I should have been. One of the other guys at the range let me try a reallllllly expensive PCP with a super-light trigger, and I was in love… except for the little thing about a couple thousand greenbacks!

      Long story short, I put in the trigger group like Gunfun1 shows along with the 1701 hammer and a lighter hammer spring. The modified gun shoots waaaaaay better than I am currently capable of, and I can shoot an entire match without changing the 12 gram CO2 cartridge. I’ll have to run some real tests to tell you guys what the velocity and target sizes are, but that’s a story for another day. It shoots as nicely as the 1701 without me having to mess with high pressure air, a plus in my book.

      • Sleepy Dawg
        Glad to hear that. It really does make a difference. Plus you can really get the trigger adjusted for your shooting style.

        And I had a high velocity and a low velocity 1720T with the 1399 stock. Really unbelievable in a sense how accurate it is and these other similar guns we are talking about.

        And do you still have the stock barrel and did you add a steel breech? And what sights do you use? Do you shoot it as a pistol still or do they allow the 1399 stock?

        Alot of questions but would like to know what setup you got.

        • I’m shooting Air Pistol Silhouette, not any class of air rifle, so I have the stock 2240 frame and grips. I did add the steel breech and a Crosman LPA rear sight. The stock 2240 front sight was too low, so I put on the front sight/muzzle brake assembly from the 1701. That includes the adjustable blade, but it turned out to be about 0.050″ too high! I put it in the mill and carefully whacked off just enough of the blade to put it in the proper adjustment range for the LPA rear sight.

          The barrel is still the stock barrel, yes. I have yet to experiment with one of the longer barrels. I’m not going for absolute velocity, so the primary advantage of having more gas expansion time is lost on me. However, there remains the fact that a longer barrel would give me a better sight radius, so that still bears investigation. It still remains the fact that in this configuration, the gun is more accurate than I am! LOL!

      • Hey Sleepy Dawg,

        (First…Welcome! Just know that B.B.’s a cat person, though generally all-around good-natured to EVERYONE!)

        Thanks for the added trigger info, which is great–especially since that was one area I did not delve into as much as the others. If your gun is already shooting better than you can, then you’re in great shape hardware-wise. If you decide you need an upgrade, from what you’ve said so far consider a steel breech so you can swap for a Lothar Walther barrel–I’m finding them to be very accurate. Though some folks also report remarkable performance from Crosman barrels, too.

        • Actually, I am a cat person myself… I have a very young orange marmalade who likes to bite my toes, but he gets a pass, he’s a rescue from the side of the road. The story of why I am called Sleepy Dawg is a long and expansive story best told over a couple of pitchers of beer. I won’t even remotely attempt it here! LOL

          The steel breech and a Williams sight was one of the first things I did to this gun, but I was unsatisfied with the mounting clamp arrangement on the Williams sight. I went to an LPA rear sight and put the Williams on the “I need to think how to make this better” pile. I’ve sketched out a couple of ideas, but nothing solid yet. As I noted above to GunFun, the stock barrel and the steel breech are more than satisfactory to my shooting (so far, anyway.)

  3. Hiveseeker,

    Again, a most excellent report. I enjoy your approach of taking on a specific aspect of something, testing it and then arriving at a fact based conclusion. The charts and graphs have been excellent.

    I have also appreciated your candor of acknowledging what you know, don’t know and be willing to theorize if there is some doubt in your conclusions. Your advice of getting a long Crosman barrel model and most all of the work is already done seems like very solid advice.

    I still think that you have some book worthy stuff in all of this. Maybe not. B.B. could offer the best advice on that. At least, your reports are a 1 stop shop for information,.. which brings me to my last point,…

    Thank you for all of your time and effort to make this happen. Mrs. Hiveseeker too! 😉 Your articles inspired me to delve deeper and when I went to look further,.. I found myself in the “swamp” of information that is out there. Thank you for navigating and filtering some of that out and presenting it in a more clear and concise manner.

    Your conclusion statements are super and spot on.

    A Good Day to you and to all,…. Chris

    • Chris,

      More than welcome, and I’m glad you’ve found the information helpful. Mrs. HiveSeeker — aka the Sassy Sandy — has been supportive and patient with having a miniature gun lab spread across the house. I’ll also say up front that none of you would have seen any of this, without her encouragement. She also comes close to outshooting me, with much less trigger time than I spend. If she practiced even a little more, I wouldn’t stand a chance!

      • Hiveseeker,

        It could be,… that she is “holding back” on you “a bit” and protecting that “fragile male ego” we “Man types” have been “reported” to have? “much less trigger time….” would be my first clue,… just sayin’. 😉

        I have told this story in the past,.. way past,… but at work there was this fellow that “knew it all” when it came to shooting and guns. He would “tout” his knowledge to well accomplished shooter’s that DID know there stuff. Long story short,.. the guy and the wife went shooting PB pistols at one of the other guy’s house that (did) know his stuff. Both shot bad. [She] listened to some advice,…. [he] did not. In no short order,.. she out shot him by a (huge) margin, several times! He got mad and they left.

        It could be that the Ladies are more apt to keeping their mouths shut and ears open when it comes to learning? You know,… none of that nasty “male ego” stuff to get in the way. 😉 Just sayin’,…. You can tell her I said that too. 🙂

        Kidding aside,.. I have enjoyed the additional comments by you and the other posters. Again,… superb job!

        Jus sayin’,…. she may be “holding back”,…. 🙂

  4. Good morning! I need to start by thanking Gunfun1 for his comment about the interchangeability of the Marauder pistol and 1720T triggers with the 2400KT, and dropping that photo in there. This is a significant contribution to this blog! And I’m glad it was posted right at the beginning of the comments — what time zone are you IN, anyway? 🙂

    • Hiveseeker
      I was hoping you would show the trigger assembly of your gun. I just know how well these triggers are. And fully adjustable on legnth of first stage pull and a crisp second stage as well as the trigger blade stop in the trigger gaurd.

      And another feature I like is the trigger pull pressure adjustment. It allows for a almost to light of pull. In other words you can almost breath and the shot goes off. But we’ll held by the sear engagement.

      And really no need to thank. Like it’s been said by several here on the blog. Just doing what we do here. And I’m in the Midwest around the St.Louis area. Which is central standard time. So that means my replys post a hour later than the time I actually reply. And I work 2nd shift now. By time I get home it’s around 1:00 am.

      • Gunfun1,

        I don’t envy you your schedule–though I’m guessing you do avoid the rush hour traffic! I’m glad it still leaves you time for some early-morning posts, to “do what we do” and share some knowledge, experience, and enthusiasm!

        • Hiveseeker
          Traffic not bad going and little to none coming home. But mostly it works out at home. I still have two daughters that live at home and the wife works days. So this way with me working nights there is someone always home.

          Oh and I still think you should make a book out of your blog reports. Each report could easily be a chapter in the book. I know there’s a lot to it. But you really should consider it. 🙂

  5. Second, I need to spread some more thanks around to B.B. for all his hard work and patience. If any of you think a guest blog is a day off for B.B., then you just haven’t been paying attention to all the photos, graphs, tables and website links sprinkled liberally throughout my blogs, not to mention how lengthy they are.

    I’m also grateful to the Pyramyd AIR blog community, some of whom have managed to stay interested in this one topic across fourteen blog installments. I’m glad you’ve found this enjoyable, and while I’ve spent a lot of time shooting several of these guns that doesn’t compare to the pooled experience of the entire community. I’ve learned something new from you with every single blog installment.

    Wow…this has been quite a journey! I still remember asking B.B. if I might be able to write a guest blog on the 2400KT, even though it wasn’t a product you could buy on the Pyramyd AIR website. I’m glad for that flexibility here–and of course, we all know where to buy all those pellets, scopes, chronographs and other accessories!

    I have to say that I’ve spent a small but significant portion of the last four years of my life putting these blogs together. I never dreamed I’d be spending this much time on this gun series, but the deeper I dug the more there was to do and learn. Each blog took me a couple of weeks at least, off and on, including LOTS of chrony work, writing, creating tables or charts, and photography. The barrel test and these last two modding blogs took me about a month each, though I have to say that I think I enjoyed the barrel test most of all–that answered a few of my biggest questions about velocities in the 2400KT.

    I might not have started if I’d known up front how much work it would be. But that’s one of the most interesting things about life–you can’t see what’s coming. If I do one more thing, I think I’d like to try a PowerMax HiPAC conversion. B.B. already covered that pretty well, but one thing I’ve learned from the community as we’ve traveled this path is that there’s always MORE to learn!

    Okay, on to the other comments and questions…It’s been fun!

    • This really has been a great series. Years ago you convinced me to buy a 2400kt and now I have three in differing levels of modification and they see a lot of shooting. In fact, one of them has been commandeered by my wife who isn’t really a shooter! Thanks for your excellent work. One thing I’d mention is that you still may get the power valve with the .22 LW barrel, at least I’m pretty sure I did.

      • Hello Rambler,

        Well, thank you for letting me know and I hope I have been a good influence (more than an expensive one!). That is great about your commandeered gun, and my wife also loves her 2400KT (though she really likes my semiauto Crosman 1077 too!). Silhouette spinner targets are our mutual favorites.

        Thanks for letting me know about the power valve you got with your LW .22 gun. That seems less common than the target valve, but is sounding more widespread than I’d realized. It was certainly what I was expecting when I ordered my HiveSeeker II, but getting a target valve–and swapping that out–taught me a lot about these guns, so it’s all good in the end.

        • It’s all experience, isn’t it? I’m really surprised that they don’t put the power valve in all LW guns. I called them up after they put the LW barrels in the 1300kt and asked them if they were going to do it in the 2400kt, and they said they had to make sure the gun was powerful enough to handle the extra lands and grooves of the LW barrel. Go figure.

    • Hiveseeker,
      Thanks very much for this excellent blog series on the 2400KT!
      Any chance we could see something similar on mods to the SSP-250? I own a 2400KT, a 2240, and a couple SSP-250s but I consider the stock SSP-250 to be superior to the stock 2240. Thanks again!

  6. HiveSeeker,

    This has been an excellent series.

    I wonder if the wide diameter of the Extended Hollow Probe might deform some pellet skirts, especially given that its length also pushes the pellet well into the rifling. The pellet that really got me wondering about this is the Predator Short, which did significantly better accuracy-wise with the wide probe.

    That pellet has a thick skirt which is also quite short. This is because the pellet has material much farther to the rear than a typical diabolo features. These would combine to make a skirt relatively less likely to be affected by the wide probe. (As far as I can tell, the other pellets have thinner and deeper skirts.)


    • Michael,

      The diameter of the hollow probe also concerned me the moment I actually saw it in hand, because the walls of the hollow portion of the tubing are fairly thin. I immediately wondered if there would be any problems seating the pellets. However, in use it seems solid enough. I will say that this bolt is very tight, and I lubricated and worked it a bit to smooth it out after installation. I am sure the tight seal is to prevent CO2 loss, and maintain velocity.

  7. HiveSeeker,

    I have a 2240 and enjoy shooting it as is. I may never do any of the mods that you have written about but it sure is good to know that I have a central source of reference, thanks to your blog, should I ever decide that it needs to be fiddled with. I can imagine how much work this was and want to express my thanks, along with everyone else to both you and BB. Thanks, guys!


    • Hi Halfstep,

      You are welcome! I’m glad to have contributed to your enjoyment of the 2240, even if you never mod it. If you decide to do anything with it, start with the Steel Breech which is one mod you can actually buy straight from Pyramyd AIR.

      While you’re at it, you might as well add a longer barrel, maybe even a Lothar Walther. And since you’ve already got her opened up, dropping a power valve in there will really boost your velocity . . . WARNING: MODDING IS ADDICTING!

  8. HiveSeeker,

    Thank you very much to the time and effort that you put into this series – it has been very interesting and educational!

    Your research and testing of the 2400KT in different configurations has provided a wealth of data and much food for thought. Though specific to the 2400 I am sure the principals and results can be applied to other platforms.

    I had to smile at your comment “the highest I could muster for this test was 76 to 78 degrees F due to cold weather. My average velocity plummeted from 525 f.p.s. to a new baseline of 457 f.p.s., a drop of 68 f.p.s.! “. You are talking to someone who lives in a climate where the temperatures can vary enough that the furnace runs at night and the air conditioner during the day… no wonder that I found Co2 to be “inconsistent”.

    BTW, “cold” is where you spit and it bounces 🙂

    Thanks again HiveSeeker!


    • Vana2,

      More than welcome. I did quickly realize that my good velocity performance was partly a result of shooting in warmer temperatures, and did not expect the velocity to drop so much at a very mild 76 degrees. That was when I started including temperature comments in my blog. Stephen Archer has done some detailed velocity testing with the QB78, and came up with a figure for .22 of about 1.8 to 2 f.p.s. drop in velocity for every degree F. But that drop appears to be higher for the 2400KT.

      One tip for you more temperate folk is to keep your CO2 cartridges warm in your pocket. Unless you’re hunting with a long interval between shots, that will give you enough warmth (and velocity) for target shooting in cold weather–though just how cold, I can’t say.

  9. HiveSeeker thank you for the well written and informative series.
    I was also temperature challenged with my recently assembled 2240. Here is the firs dozen shot from it and it show some accuracy potential. Shooting in 30 degree weather meant take two shots and warm the pistol up. Me and the pistol are ready for warmer weather.

      • GF1
        I used Ruger super points at about 35 feet. I had the bottom of the grip on my hand that was rested on a bench. Some have called it a tea cup hold.

        • Gerald
          I have used that hold with pistols.

          And good groups. Have you tryed any other pellets by chance? And if I remember right you just got this combination on your gun recently. Do you plan on staying open sights?

    • That’s not a bad start, especially dealing the the variability of those colder temperatures on velocity. I must confess that I’m terrible with pistols. I cheat a lot with those carbine stocks. Four of my five 2400KTs have them.

      • HiveSeeker I have the stock adapter to put on but I am going to enjoy this one as a pistol for a while. I am thinking of using the dimensions of the stock piece to make a wood one under the banner of how hard can it be. Gerald

        • Part of the reason I ended up buying my first 2400KT was because I was replacing a 1377 that had that carbine stock. But I would also sometimes change out the stock and shoot it as a pistol. I love the versatility of these guns!

        • GF1 The group posted is because I was itching to try out the new assembly. When it gets warmer out I have several pellets to try. As long as I keep it in pistol form I will probably stay with open sights. If I put on an optic I will also add the #1399 stock. Then it will look funny and I will need a longer barrel.

  10. Hiveseeker,

    Great report! I wish all PCP manufacturers had the same philosophy toward their product as Crossman. Let’s build a platform that can be the basis for whatever the customer wants it to do!
    Thanks again for putting in all the time, effort, and money into all the different versions of you pistols.


    • Yogi
      That’s one thing to look for in a gun if your a modders. How easy it is to get parts you want. And the more parts that are available the better.

      That’s what it was like when I use to mess with muscle cars and building race engines. Chevy’s and the small block Chevy engine had so much aftermarket stuff available it was almost rediculous. But you sure could build whatever you wanted.

      Well that’s how I look at the Crosman guns that have been mentioned throughout Hiveseekers reports. Crosman definitely understands part changeability. And that does make it better. And what’s nice is Crosman for the most part keeps parts in stock. So as long as you get a part number from one of their drawings. You can buy it from them. Well there are some guns that are older that they ran out of supply. But that’s normally the case.

    • Yogi,

      Thanks for your enthusiasm! Yes, it’s been an investment of both time and money–not sure more of which!–but spread across four years at the pace of about a gun a year, not too bad. For a custom made product and considering the build quality, these are a bargain. There are certainly more expensive hobbies!

  11. Awesome presentation. Derrick keeps trying to get me to buy one of these guns, and I can see why.

    ChrisUSA, great point about the ballistic coefficient as the factor that separates some projectiles over distance. If there is any one factor at work, I would say this is it. It actually interacts with wind in the form of onrushing air so that the air is connected to the load and there is no longer action at a distance. But I’m also pretty certain that ballistic coefficient cannot be the only factor. A flat shooting trajectory is closely related to a good ballistic coefficient although I’m not sure they are the same thing. So, other things being equal, is a flat shooting round always more accurate than one with a looping trajectory? I don’t know if that’s true. It’s definitely harder to move between distances with a looping round and find the correct holdover. But if you’ve had the chance to zero both loads, I don’t see why a looping trajectory couldn’t be as repeatable as a flat shooting round. B.B. said that he could hit a dirt clod at something like 90 yards with a .38 once he got the holdover figured out.

    One cause of a looping trajectory could be a heavier bullet. On the other hand, a heavier weight would be more stable in the wind which would favor the round over longer distances. By the same token, a flat shooting high velocity round is generally lighter and will move more easily. On the other hand, the smaller round spends less time in the breeze than the heavy round. There are so many conflicting factors here along with some completely different variables that I haven’t thought of that I doubt you could figure out the right load for a long distance round from pure reason, but only through experiment.

    Nevertheless, I suspect that, whatever the answer is, the ballistic coefficient plays an outsize role in long-distance performance. One compelling bit of evidence is the great success of 6mm rounds which seem to hit some sort of sweet spot for accuracy. I had heard that the 6mm benchrest was the ultimate round that outshone all others. But now the 6.5 Creedmoor seems to be getting a lot of attention.

    I’m not sure how these principles would translate to airgunning. Given that pellets rely much more on drag for stabilization, my guess is that the role of the ballistic coefficient would decrease proportionately, but this is highly speculative.


    • Hello Matt61,

      I wish my backyard was big enough to really mess around with ballistics at range! I’m limited to 20 yards, but would like to retire on “a bit o’ land” when the time eventually comes and set up a nice home range. I’ve always been fascinated by long distance shooting. I’m terribly detail-oriented and would probably end up weighing and sizing pellets, getting an anemometer and portable humidity meter, and really digging into ballistic coefficients. No squirrel would be safe–as long as I have my calculator with me!

  12. HiveSeeker,

    Thanks for the reports. I have learned a lot from them and they have helped to keep my brain active. I expect at lest one more down the road.

    I am sure this will not be the end of your mods and will be going in other directions in the future. Maybe time for some PCP mods.

    Thanks Again

    • Benji-Don,

      More than welcome, and glad it’s kept your brain active–it sure has done the same for my laptop and chronograph! I’ve tried to keep things fun despite throwing a lot of physics around. I am looking at the HiPAC a bit, which looks like a super easy mod if you’re not going more than 1800 psi.

  13. BB,

    I know you are still using the Air Venturi Compressor and will be providing updates. Do you know anything about this?

    “Air Venturi Dry Air Intake Filter for the AV 4500 psi Compressor by Hill Pump

    Fits Air Venturi Air Compressor, Electric, 4500 PSI/310 Bar, 110V and 220V
    Easy to install
    Removes potentially harmful moisture from air before it enters your compressor
    Uses two (2) Hill Dry-Pac media refills (included)
    Made in UK

    Protect your Air Venturi 4500 psi Compressor from potentially harmful moisture with the Air Venturi Dry Air Intake Filter by Hill. The Dry Air Intake filter removes moisture from the air as it enters your compressor. This significantly reduces the chance of moisture entering your tanks or PCP cylinders when you fill them. Easily installs onto the Air Venturi 4500 psi compressor in just minutes. Includes a stand, hose, and enough Hill Dry Pac media to fill the filter. ”

    Is PA going to provide one of these free to the early owners of this $1300 compressor now that they know that it may not be safe to pump AIR with it? Should I stop using mine until they do?


  14. HiveSeeker,

    Great run of 14 Blogs, loads of information thanks so much.

    Looking forward to 15, well you said you wanted to wrap up the series but there is always more to say, so if you come up with more we are willing to listen to any new input.


    • Hello Mike,

      Thanks, and no solid plans for more at the moment. Fourteen installments was way more than I ever expected–the project just grew! But, we shall see.

  15. Hiveseeker,
    with the muzzle break, if one was to use open sights, does the steel post on the muzzle brake give a better sight picture than the stock type plastic blade cheap sight?


    • Hi Doc,

      Truth be told, I have never used open sights on one of these guns! However, the sight pin seems to be about as wide as the blade on the regular plastic sight from what I can tell from photos. I have shot these with no sights at all during chrony testing, and the front sight pin seems sharp and clear. If there is any actual difference, I would guess that the muzzle brake sight pin is the narrower.

    • I can address that! I put the muzzle brake assembly from the 1701 (Silhouette) on my 2240. It has a blade that can be rotated to change the apparent width of the front blade in the rear sight. It works VERY WELL to improve the sight picture over the stock plastic part. Expect that you will have to do some filing or milling of the front blade to get the relative heights into the useful adjustment range, however.

      I don’t know that the blades on the custom shop muzzle brakes look like, they may not have the adjustment feature of the 1701 front sight.

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