Meet my new "Fatboy" valve + Custom Taipan Veteran build

Forums PCP Airguns Meet my new "Fatboy" valve + Custom Taipan Veteran build

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    mtnGhost
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    Let me preface this by saying that this Vet and I got off on the wrong foot when I first received it. I came close to parting with it, but I stuck with it and started uncovering it's potential, while realizing just how well made these things really are!

    I spent a couple of months in my spare time this winter playing around with it, and eventually figured out what I needed to change. I got busy prototyping custom parts for it, each one undergoing several revisions until I was satisfied with the level of perfection with each one of them.

    Here's my current configuration:

    Current Barrel: 600mm FX STX Barrel (slug A) + Custom FX barrel kit adapter

    I can get away with the length of the 700mm without too many issues, and I can also generate tremendous power for using the 500m, but 600mm seems to work best for me as a hunter. This particular 600mm kit is from the FX Crown that I bought from @bob_o a while back. That barrel had always been real good for me, and I knew that it would be solid for eliminating anomalies during my testing.

    Here is the 600mm without the Taipan moderator..

    and another random photo with the 500mm barrel kit + DonnyFL moderator (Tatsu or Sumo, not sure)…

    Adapter…

    This took some time, trial and error to materialize. I started off with a plan for making a drop-in replacement for the FX brass TP inlets, but that left me with a really flimsy adapter. I grabbed some graph paper and sketched out some ideas, then made them on my lathe. The next version that I made was a full-size replacement for both the stainless adapter and brass inlet (combined into one piece). This version (aka v1.0) featured an integrated seat for the barrel liner. I did comprehensive testing with the v1.0 (and a v1.1), but determined that the projectile seating depth was not right with the gap between the Taipan's little aluminium transfer port piece and the liner. In v2.0, I eliminated the seat and made some other small modifications to get it perfect. Here are v1.0 and v2.0:

    More of v2.0…

    This adapter has made me VERY happy. Harmonics are not an issue for me, I suspect the solid brass adapter is doing a good job of absorbing a lot of the shock.

    Taipan Moderator

    I was dead set on using the factory moderator. I swapped the muzzle thread out with Donny's 1/2-20 adapter, and when you combine the Taipan moderator with anything = it's the quietest thing that I have ever had! That said, an interesting challenge that I ran into was figuring out how to use the Taipan moderator with the FX STX barrels. The FX barrels are ~13.5mm OD and The Taipans are ~15mm. Luckily, the two can mate since they're both 1/2-20, but the inside diameter of the moderator is larger than the OD of the FX sleeve – leaving a big gap between the end of the moderator and the FX barrel sleeve.  Naturally, this would cause the shooter to get shot in the face by air and lead dust (and no, I wasn't dumb enough to fall victim lol)

    The simple fix for this – I kept the shaft collar from the inside of the FX barrel shroud, stuck a ~14×1.5mm o-ring in front of the collar, so it gets sandwiched between the back of the moderator and the collar (thus sealing the gap). It doesn't look pretty, but it's perfectly functional. Eventually I will prettify it, but it's not a priority for me at the moment.

    Custom "Fatboy" Valve System

    I'm incredibly impressed with how this new valve system has turned out. The power gains are substantial over the factory vale system (90+ fps!), and the shot count increased on average by 11 shots per fill.

    For this valve body, I'm also using the harder 485 marine brass (more scratch-resistant than the softer factory valve bodies), and the valve stem is made from (Ketron) PEEK on a tapered 6AL-4V titanium valve pin (weighing 1.1 grams!). The sealing surfaces are using an interference fit with offset angles, which provides MUCH better sealing properties between these two relatively hard materials (you typically see a hard and soft material with valves, but these two are like diamonds lol). The head on this valve body provides much better valve compression and performance (consistency, efficiency, and shot count). The length of this pin has also been optimized for the stroke.

    For comparison, the factory valve is on the left, the middle one was another prototype, and the Fatboy on the right:

    Two 20cc Power Plenum Extensions

    Rocking two of Ernest Rowe's Taipan power plenums for this build. I can get away with not using any, but I've chosen to use them when I have a 600mm or longer barrel installed

    Hammer System / Springs

    This is where it gets interesting.. I had defaulted to a big heavy spring like the other power tuners. Then, I decided to spend some time on testing different springs, brass weights, and polymer spring tensioners. I found that I can achieve 1-2FPS ES using a smaller spring, with a 3 gram hammer weight (with the little black POM-C guide at the rear) at the cost of limited FPS tuning range. The factory spring with the brown POM-H / Delrin spacer / bushing not only produces as much power as the heaviest spring that I could fit, but it also allows me to tune this Taipan down to as low as 315FPS! LOL .. quite the power range from simple HST adjustment!

    Regulator

    I'm running a Huma reg in my Vet. It provide a little more room for air, and I can tune it easier than the factory reg. There's nothing wrong with the factory regs, this is just personal preference.

    More to come..

     

    • This topic was modified 1 month ago by mtnGhost.
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    zx10wall
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    Let me be the first to say, I’m impressed. Thank you for sharing all of these trials and mods with us. 

    • This reply was modified 1 month ago by zx10wall.
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    sonny
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    Incredible!

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    JoeKool
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    Kool!

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    sturba
    Blocked
    Blocked

    Apex hammer/valve gun. Just wicked cool!

    Add the Taipan trigger box and we’re in “yeah but nothin” territory

    I am a collector, not a shooter. After the test and tune, I intend to try and buy this gun 

    • This reply was modified 1 month ago by sturba.
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    Kaeokini
    Participant
    Member

    Aloha mtnGhost,

    Very impressive in your build. Let me know when your taking orders so that you can do your magic on my Taipan. 

    Aloha,

    Keone

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    DanielL
    Participant
    Member

    Nice work.  You ended up with a very versatile gun. 

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    edosan
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    Nice work!  you copycat! jaja (just joking)

    • This reply was modified 1 month ago by edosan.
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    CampFussell
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    Man, to have just 0.01% of your machinist skills would be a blessing for this ol' fart.

    Awesome work you have done!

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    L.Leon
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    Member

    Incredible work, you are obviously a very talented individual. Amazing craftsmanship, thanks for sharing…

    • This reply was modified 1 month ago by L.Leon.
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    Vetmx
    Participant
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    I enjoy reading what you have done with your Taipan but I ain’t touching mine. It’s the only gun that was perfection out of the box that I ever owned. 

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    Centercut
    Participant
    Member

    Nice work Ghost. Impressive!!!

    Mike

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    biohazardman
    Participant
    Member

    You have put a lot of werq into that gun to make it what it is.  Pretty impressive job you have done. 90fpe should probly be enough and being able to tune is a definite plus great job.  Thanks for the read and pics.

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    Motorhead
    Participant
    Member

    Personally had done very similar work on the TAIPAN MUTANT what is now 3-4 years ago.  Same sorta stuff with a valve poppet redesign using Peek, changes in throat specs too.

    Plenum was made longer withing the limits of vent hole already in tube.  * It too gained power, gained shoots and just improved an already great platform into something better yet.

    It was on the old TALON forum and not sure it even exists any longer ?   Photobucket hosting issues & all.

     

    NICE WORK !!!  on the Veteran very nice.

    knowing that it takes a lot of fiddling trial & error to find what works and what is not worth the effort.

     

    Scott S

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    SniperX
    Participant
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    Can you please share how you secured the valve stem to the Ketron plastic?  Is it an interference fit, or epoxy?  

    The forces involved are high so Im just curious whats involved in keeping the stem from slipping or coming out. 

    Thanks for the great post!

    • This reply was modified 1 month ago by SniperX.
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    mtnGhost
    Participant
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    I want to thank everyone for the positive feedback! Everyone except @edosan, who is always taking credit for everyone else's work .. (kidding of course! 👊🤣 ). I should probably thank Derrick as well for enduring my text messages during this build, while I worked through some if the ideas 😆 

    Anyways, it's been a fun journey building parts for this rig, and unbelievably rewarding to see the end results as they are. The form factor of this rifle is right up my alley, and like I mentioned to another member last night – I never expected to match the power output of the MKII that I built last fall, but low and behold I have indeed put it on that playing field. 

    I'm planning to do a small production run of parts soon, so just contact me if interested so I can get an idea how many kits to produce.

    @motorhead – thank you sir! And UGH, Photobucket about ruined the internet with their frigging monetization scheme! I can't count the times that I've cursed them trying to find photos as I have searched for things, where the only photos were hosted by them (and long gone)! LOL

    I know exactly what you mean about the atmospheric breather port. I'm not quite sure how many extra CC's that one can squeeze out if it by spacing it out, but I'm just very happy that Mr. Rowe had produced the 20cc drop-in extensions so I didn't have to do much with the plenum chamber. I also have a pristine little Mutant sitting here as well with a perfect CZ barrel..

    I love it as it sits! A very "civil" and pleasant shooter… but I really have to hold back from going all out and super-turbocharging it 😂

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    mtnGhost
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    SniperX

    Can you please share how you secured the valve stem to the Ketron plastic?  Is it an interference fit, or epoxy?  

    The forces involved are high so Im just curious whats involved in keeping the stem from slipping or coming out. 

    Thanks for the great post!

    The pin that I'm testing right now is just pressed fit. When I'm confident in the overall design, I'll add a little Loctite 680 for added security. Given the properties of this PEEK and titanium, I would not doubt that the press fit would last forever 😆 

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    mtnGhost
    Participant
    Member

    Length

    I had a couple people ask me how long my Veteran is. In the primary configuration with the 600mm barrel with two plenum extensions, it measures out to:

    Without Taipan moderator screwed on: 31"

    With Taipan moderator screwed on: 34.4"

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    Veerkracht
    Participant
    Member

    Very nice work!

    You know your way with the lathe.

    Impressive fpe.

     

    Regards, Robert.

     

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    mtnGhost
    Participant
    Member

    Veerkracht

    Very nice work!

    You know your way with the lathe.

    Impressive fpe.

     

    Regards, Robert.

     

    Thank you! The valves take a lot of time on a manual lathe, but CNC is the next step in a couple of weeks. 

    This is one below gave me another increase in velocity, pushing 28.5gr NSAs at 992FPS with the 600mm FX barrel for 62FPE:

    The spread and deviation is real tight, and I couldn't be happier! I went out today to test at paper, and stress test the valve a bit. When I got down there, the wind was blowing ice / hail sideways 😬 .. 37F, very wet the wind at 50-60+ MPH all day long (we're having a nasty Pacific storm here in Washington state today). I didn't want to drive out there for nothing, so I nailed a target at 100m and shot some groups anyway 😆. 

    Even with this wind, once I got zeroed – I was shooting 2" groups with the 28.5gr NSAs (tuned for 980FPS). My hands were frozen after the first fill, I left the HST where it was and loaded a mag of 24.8gr NSAs, but they weren't grouping as tight. I refilled again, looked in my ammo box, and chose to load some of the FX Hybrid slugs for fun. Waited for a break in the ice storm so I could get out my LabRadar again. Decided to dial HST back 1/2 turn for air conservation, and they registered at 1040FPS.    I had to hold a lot more to the left, but keeping the same POA – they also shot 2" in the crazy wind!!! 

    Now I'm dying for my next opportunity to get back out there. I wouldn't normally shoot anything but .30 cal in weather like that, and to see a .217 perform like that is 💪💪💪

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