This is going to be a long thread - bitza build - can you guess what it is yet ?

[nurek]

Looking good Jon!

[oldskoolzzz]

Cracking stuff JB

[Shed tuner]

Looking good Jon!

Not quite up to KT's prototyping / fabrication skills though, I know !

[nurek]

Not quite up to KT's prototyping / fabrication skills though, I know !

Fingers crossed the KT muzzle brake will fit when you find the right barrel!

[Shed tuner]

Fingers crossed the KT muzzle brake will fit when you find the right barrel!

now there's a thought !

[Shed tuner]

Just a few things done today...

Took the gamo trigger out and did the RC bearing mod, as it was terrible. Now it's lovely and light, but still no discernable second stage. I need to introduce one somehow, but with a bit of moly and the bearing, at least it's very smooth and light.

Found a stock


Trimmed down the trigger cage to make the inletting easier. Will break out the router at the weekend.. too crowded in the workshop to do it in there.




And I've decided on the donor barrel, from a FWB300S, as it's already blued and accuracy is assured.

I've also realised I need to make a trigger guard.. that can wait... This might be a working gun by Sunday; it'd be nice to take it to the range...

[TonyL]

Looking good already, Jon. And, as you say, accuracy should be assured with the 300S barrel.

[Shed tuner]

...alive I say.


Finished machining the barrel this morning, and with a quick tweak of the hammer spring it;s doing 10.5 with JSBs. Will have a few hours work to do checking and flattening out the power curve, but whatever.. I have a working air rifle from a pile of bits.. I feel like I've just had another child This is certainly the most ground-up build I've done to date.





Next job is the stock, then the two stage trigger, trigger guard, and the cosmetics (barrel support, reg cover, find some grub screws for the barrel), and a mod or stripper. And the power curve.

[oldskoolzzz]

Cracking JB

[Craig-P]

Tremendous build mate, well done.

[Papa g]

...alive I say.


Finished machining the barrel this morning, and with a quick tweak of the hammer spring it;s doing 10.5 with JSBs. Will have a few hours work to do checking and flattening out the power curve, but whatever.. I have a working air rifle from a pile of bits.. I feel like I've just had another child This is certainly the most ground-up build I've done to date.





Next job is the stock, then the two stage trigger, trigger guard, and the cosmetics (barrel support, reg cover, find some grub screws for the barrel), and a mod or stripper. And the power curve.

Loving it best thread I’ve seen in a long time! This stuff really floats my boat.
Regards Graham

[gtfreight]

It just amazes me when I see the skills that you and others on here have.
If I had 10% of your expertise I would invest in some proper machinery and have a go myself but sadly it would be just taking up room in my garage.
I can't wait to see the finished creation.

[TonyL]

Awesome! I bow at your feet, sir. Very well done.

[Shed tuner]

Had a look at the power curve today, and frankly it looks like I got lucky with my semi-informed estimates on valve return spring selection/strength, port sizes, hammer spring, etc...

After some basic tweaks, here's the power curve with a max 200 BAR fill.

Shot - power
01 - 10.8
06 - 11.0
11 - 11.0
16 - 11.2
21 - 11.2
26 - 11.2
31 - 11.5
36 - 11.7
41 - 11.5
46 - 11.4
51 - 11.3
56 - 11.0
61 - 11.0
66 - 11.0
71 - 10.7

Knock off the first and last 5, that's 60 shots in the 11.0 - 11.7 range, which is about 17 fps. It's a fairly small cylinder (around 120 CC ?) so very happy with that.
It's pretty much perfectly symetrical, and centred in the middle of the fill, so nothing to adjust there

I've turned the hammer down 1/4 turn, which should result in a max fill of 185/190 bar, and a couple more shots in the sweet spot. If I see evidence of the "peak" on the target at the range, I will have to choke the port down a fraction - it's currently 2.5mm, so 2.2 or 2.3 should do it. there's a couple of ways to acheive it on this gun.

Stock inletting is done, just needs a bit of sanding and tidying up, and drilling for the main action screw - currently waiting for the glue to dry as I had to bung the pre-existing hole as it was half-a-hole out, before redrilling. And a I need a trigger guard, then I can take it to the range !

[les allam]

Nicely done Sir
And a very useful and consistent shot count .
Looking forward to the finished product.
Les..

P S
Please bring it with you to the May Boinger Bash (if you’re going)👍.