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Project Cp Bitsa Target Pistol

Discussion in 'Air Pistols' started by Nubble, Jan 20, 2019.

  1. Nubble

    Nubble Donator

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    CP ‘Bitsa’ Target Pistol

    [​IMG]

    Now I like the idea of a target pistol with a stock that is a little more contoured to fit my hand and I’m not scared of a bit of woodwork, in fact I love fiddling. I also like the idea of making things from ‘stuff’ that you already have lying around (or what I refer to as ‘valuable stock items for future use’). I was reluctant to start chopping the stock of my CP1 so I thought I would have a go at making one. “Can’t be that hard can it?”


    I had a few ‘Bitsa’ CP1’s and CP2’s kicking about so that started me wondering if I could make a fun target pistol out of the parts I had. This consisted of a .177 breech, bolt and barrel plus an air tube.

    I needed to make or find from somewhere; a stock, a trigger and sear, a hammer tube end cap and a spring guide. I already had a spare valve assembly but with a leaky Co2 seal so first things first I sourced a seal from Ped. Cheers Ped.

    Next the difficult bit of making a stock. I had a root round for a suitable piece of timber and found a piece of scrap 6x2 that wasn’t too knotty and had fairly straight grain but it had a slight split in the centre. I thought I could work round this and besides, nothing too fancy for my first go.

    First an outline was drawn using the CP1 stock as a template. Then I drilled the 22mm hole into the stock that will support the air tube. My pillar drill doesn’t have the reach needed so I had to cobble summat together using a couple of workmates, No – not those kind of workmates, I mean Black and Decker workmates. I had to judge the depth bye eye with some careful measuring and guessing whilst trying to make sure I had a perfectly err ... ahem, square hole!

    Once drilled I cut the profile roughly to shape using a hand saw, then using a 40grit flap disc in an angle grinder I put the major shaping into the stock trying it for fit every now and then. This took an hour or two. I then spent the next week or so (evenings) sanding the stock to the shape of my hand as much as I could. I used a Sealey rotary tool for the most of it using the 12mm sanding barrel band thing and I made lots of dust! Once I was finally happy with the overall shape (never totally happy) I still had an area around the trigger that remained unfinished because I had no trigger, so next I needed to get a trigger and sear before I could finally finish the stock.

    [​IMG]


    [​IMG]

    I found a piece of 6mm steel plate and using the trigger from a CP2 as a guide cut a trigger and sear out using a 1mm disc in the grinder. The plate needed to be reduced in thickness from 6.2mm to around 5.6mm. I lightly stroked the flap disc across a few times and finished by hand with a 6” file as was 90% of the shaping to both trigger and sear plate. I used a grinding disc in the grinder to get a rough concave shape to the trigger and then filed with a 6” half round file. I then went over with a 4” needle file to remove the burrs and gouges before polishing the sear with wet ‘n dry. I used a fine whetstone on the bench grinder to put the small 20° bevel for the hammer at one end of the sear [hammer latch] and then finished with wet ‘n dry. I didn’t bother polishing the trigger as I just wanted to see if it worked or not so you may still see scratches in the photo!!

    [​IMG]

    I managed to reproduce the 2 stage operation so my design is as the original although I admit to the fact that the 1st stage hole that runs at an angle thru the trigger is about half a mm off centre which really bugs me. Having said that I’m happy with the overall effect and it does the job (hopefully).

    The trigger spring locating hole was drilled in the sear and I drilled the holes for the locating pins in the trigger.

    [​IMG]

    I also tapped out the holes in the trigger housing (the bit welded to the air tube). I used flat bottom grub screws to replace the original locating pins (which I didn’t have). These are a perfect fit, they finish it off nicely and look like they should be there. The trigger was assembled with taper point grub screws for the 1st and 2nd stage and one of my light springs cut to 10mm.


    I had an original CP2 end cap but these are crap and I didn’t want to use it so had to now try and work out how I could overcome the problem. Long story short I found something round just 1mm less dia so I used that. I cut it to length then drilled a 4mm hole in the end (outside) of the end cap and straight thru the body (side) at 90°. I then sunk a 12mm hole in the opposite (inside) side to provide the recess to locate the spring guide. The outside hole was tapped to M4.


    The closest thing I had to a spring guide was an M8 coach bolt. With the bench grinder I gradually reduced the head of the bolt to fit the 12mm hole in the end cap and then removed half a mm off the shank diameter before cutting to length and finishing the end. If my calculations are correct the base of the guide and end cap project out into the body (hammer tube) by a couple of mm more in the theory I will have less play past the point where the hammer and trigger engage and I can also reduce the length of the spring slightly.
    This shows the spring guide and end cap before tidying up.
    [​IMG]

    Test fitting everything into the stock for the first time I notice that the stock was pressing against the base of the sear plate. I also noted the position of the trigger. The action was removed and the final shaping done. The whole stock was then sanded to remove any scratches or blemishes. It was then given 4 good coats of Nath’s gunstock oil leaving 24 hours between coats. Then a good few coats of Nath’s gunstock wax rubbing it in well into the grain using my finger. For a crappy piece of timber this really made the grain pop a little more.

    I cut one of my light hammer springs to a calculated 65mm and assembled everything with a final clean and lube. I had an old Hawke red dot so popped that on rather than using open sights and fitted it as far back as I could. I also fitted the standard mod that comes with the CP2.





    Shooting it...


    I still needed a trigger guard but I couldn’t wait to try it out the first chance I had which was today. It was cold, damp, very light drizzle and horrible but I just couldn’t wait. I rattled off 40 shots, tweaking the sights and just playing. I then shot another 60 or more with it on a bean bag. We are now up to 120 shots and still the same Co2 bulb. I did away with the bean bag having got it somewhere close and shot 1 handed until the bulb ran out. Trouble is it didn’t!!!!….. it got dark. I was up to 200 shots from the same bulb and it was still going. Blimey! I was expecting a high shot count but not quite that high.

    [​IMG]

    The trigger works fine. There is a tiny bit of lateral wobble but this I don’t mind as it was really an exercise to see if I could actually make one that works! Now I’m thinking of making one in brass that is set back a little more and a better fit. Trigger pull is light. A nice few smooth mm of 1st stage before the firm but light resistance of the 2nd stage.


    The gun cocks nice and easy, the bolt locates positively when pulled back and travels around 1mm past the point it needs to so all good there.


    I think the spring or spring guide may need modifying. After around 160 shots the spring guide dislocated and I couldn’t cock the gun. I quickly took the stock off, then the end cap, re-seated the spring guide and carried on.

    Overall I am very happy with it. The stock fits very comfortably in my hand with either thumb up or thumb down. I would have preferred a little more width around the base of the grip. Next time perhaps. It has kept me occupied for more than a few evenings and the best bit is that the only item I had to buy, other than the Co2 seal was an M4 stainless steel cap bolt for the end cap.

    Now that bit I like.



    The most annoying part of all was the stock. The inside relief and shaping I was very proud of when I first cut it out. All by hand and perfect to the mm. When I came to fit the action I found that the trigger housing (the bit welded to the tube) was welded on at an angle so I had to continually keep shaving bits out here and there to make it fit right. This took ages, flippin ages and the results, even tho you don’t see ‘em are not as pretty as I would have liked. Having said that the action fits with a satisfying dunk as it finally locates into place. I also think the stock would have looked better darker and I fancy a go at stippling too.


    200 shots and still going...

    [​IMG]


    Well done if you stuck it out this far. Hope it wasn't too boring!

    Cheers
    Nubble
    :thumb:
     
    Last edited: Jan 21, 2019
  2. mikeyhall1

    mikeyhall1 Amazing Poster

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    Nubs that’s superb buddy, I really enjoyed reading this and the work is most impressive.
     
    Nubble likes this.
  3. Nubble

    Nubble Donator

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    Nice 1. Cheers Mikey.

    My first vote lol. :thumb:

    It's been very enjoyable to build. At times I have been more excited than you at Christmas at the thought of completing one part and moving onto the next. ;)
     
    Blue BSA and mikeyhall1 like this.
  4. Dennyboy

    Dennyboy Engaging Member

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    Nice work..:up:
     
    Blue BSA and Nubble like this.
  5. Nubble

    Nubble Donator

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    Thank you very much.
    :thumb:
     
  6. That hurts

    That hurts Barely Active

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    Not bad for an amateur I guess ;):D Bloody nice bit of work their Nubbs :up:
     
    Nubble likes this.
  7. Nubble

    Nubble Donator

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    Amateur indeed, praise indeed.
    :thumb:
     
  8. Nubble

    Nubble Donator

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    EDIT
    One thing I forgot to mention is just how delightfully quiet it is. I couldn't believe it the first time I pulled the trigger. The pellet hitting the paper target was louder than the gun. I will chrono it at some point to see exactly how low it is running.

    Cheers all
    :thumb:
     
    That hurts likes this.
  9. QuoVadis69

    QuoVadis69 Donator

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    Fantastic work mate ! :up:
     
    Nubble likes this.
  10. Nubble

    Nubble Donator

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    Nice 1 QV.
    Cheers
    :thumb:
     
    grahamtdi likes this.
  11. grahamtdi

    grahamtdi Member

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    I enjoyed that being a biased cp2 owner ,Thanks
     
    Nubble likes this.
  12. ped

    ped Keyboard Hero

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    made a nice job of that
    I'd keep an eye on the contact point of the sear for wear and it would be best hardened but you'd have to case harden it
    might even have a cp1 trigger guard in my spares box
     
    Nubble likes this.
  13. pjgtech

    pjgtech Sleep, eat, work, eat, chillout, sleep, repeat.

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    Nice write up, thank you. :thumb:
     
    Nubble likes this.
  14. Patton

    Patton Jack Reacher's big brother

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    Thar looks great. Nice work.
     
    Nubble likes this.
  15. Nubble

    Nubble Donator

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    Thank you. I can't believe how much I enjoy shooting these things.
    :thumb:
     
  16. Nubble

    Nubble Donator

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    Cheers @ped

    I might like that trigger guard off you. Been wondering what I could find to make one from ????

    I'll heed your advice and thanks for the seals. It was that seal that started the project off! :D


    :thumb:
     
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  17. Nubble

    Nubble Donator

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    Thank you Peter.
    :thumb:
     
  18. Nubble

    Nubble Donator

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    Thank you very much Patton.


    All of your comments are very much appreciated guys.

    :thumb:
     
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  19. ped

    ped Keyboard Hero

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    i'll have a look for it my mate John does brass ones though if I can't find it
     
    Nubble likes this.
  20. Rm29

    Rm29 Currently obsessed with silencers

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    Great job. I like it, you can now make me one with the rest if your spare bits.

    Rich
     
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  21. Nubble

    Nubble Donator

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    Cheers Rich. ;)
    I'll have a root around on the bench see what I can find. :D

    :thumb:
     
  22. Nubble

    Nubble Donator

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    Addendum.

    Photo showing trigger housing. Pins removed and tapped to M3. Should have taken pic from underneath but you get the idea.

    [​IMG]

    :thumb:
     
    Patton likes this.
  23. Dag

    Dag Pro Poster

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    Excellent Nubbs! One could almost believe you are hooked on CP1's!
    Thanks for such an entertaining and informative article.
    Jim:up:
     
    Nubble likes this.
  24. Paul55

    Paul55 Keyboard Hero

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    Wow, what a great read & an awesome job with your build. I can't wait to get my own CP1, I've got your spring kit waiting & ready.
     
    Nubble likes this.

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