Japanese pumper?

[Jirushi]

Hi,
I picked this pumper up during my holiday in England.
I think it is Japanese; attention to detail, quality design, wood - all similar to my Sharp's, Heirinkan and Taiyo Juki's.
Can someone perhaps help with identifying it?
SKB? There are only a few numbers on stamped on the metal and the woodwork; no brand name.
Many thanks,
Louis

[Jirushi]

Ps. After returning home, I started to clean/repair the gun.

Parts pre cleaning



Detail of the valve internals



None of my non-Japanese pumpers or CO2 guns have this feature: a threaded valve stem. Makes so much sense. I guess the only reason not to do it, is to save money?



Not sure if this is original or a mod, but after fitting a new o-ring, it works well.



The safety mech. Turning a knurled steel ring so that the slot is in the position of the trigger, means the trigger can be operated.
The spring loaded ball bearing was missing; I took it out of a foster quick fill coupler.



Nice rear sight. Can be moved up and down on the barrel. An aperture would have been even better. The rear part of the action has two threaded holes on the side; probably for fitting a Crosman S331 type aperture sight.

[Jirushi]

Markings on the stock:

[Jirushi]

A smart feature:
a slot where the brass valve part goes, to align the transfer port. This photo is looking from the rear of the action towards the front.

[Jirushi]

Just need to work on a few things:

- there is a blast of air via the stock nut and the trigger, on the shot. Via the valve stem? Via the valve nut? Or both. I will try a small o-ring around the valve stem first.
The rubber ring that goes between the brass valve part and the valve nut, is difficult. I always have this issue with Sheridans, where it is a lead seal. These seals make it very difficult to turn the valve nut back on. I used a much thinner o-ring, which might not be sealing well. 

- try different seals in the valve stem. I am now using two seals for Sheridan C check valve (with the hole in the middle). On top of each other. Not a very "neat" solution. I have a good polyurethane seal with should work.

The gun is now doing 600 ft/s with 15.89 gr (.22") JSB. On 8 pumps. That's 12.9 ft/lbs. Without the air wasteage, it will be a bit more.
The pump arm is overcamming nicely; not too much.

The safety is nice; you can operate it with your thumb, whilst holding the gun in shooting position.



Plus when you cock the gun, the hammer spring guide slides out of the rear, showing a red band; this way you can easily see whether the gun is cocked.

[19Sheridan57]

 Nice looking rifle. 600 fps with that heavier pellet is not bad at all. I have no idea if that is on par with a new one, but I think it is good.

[Pellet Fun]

That’s a nice piece of kit. I’ll have to follow along to see what others have to say on its history.

That compression spring and internals look to be very stout. I like it.

[JoninMA]

Any chance it could be a Spanish Setra(sp?)? Looks well built, but that rear site doesn't look Japanese.

[oldair]

Louis, there was a small discussion of this gun on the BBS in 2020- if you got it from Ratbuster:
https://www.airgunbbs.com/showthread.php?871730-Can-anyone-identify-this-air-rifle&p=7928251#post7928251

In my stash is a very similar one shown below, also with no markings.  The two SKB's I've seen have different features and are marked with their logo, so I'm quite sure these came from a different manufacturer but I think from Japan as they're better built than Philippine or Indonesian stuff.  Definitely not a Setra; they're more a Sheridan copy.

Don R.

[45flint]

You get the most interesting pumpers!  Your a pumper magnet. Lol.  Never a gun that you don’t take completely apart either

[Jirushi]

Thank you gents for the suggestions and feedback.

@Don R., it is indeed the gun from that thread on the UK forum. Thank you for posting a photo of your very similar looking gun. In fact, I think it is the same except for the trigger guard.
Interesting to see the front sight part that screws into the hood to secure the post (if I am using the correct terms). On my gun, the black part that is sticking out, has probably snapped off. What remains on the inside of the hood, seems to be a sort of plastic?

I am 99.9% sure it is Japanese.

Biggest challenge now is to solve the air waste from the valve nut / notch.
That hole on the left... I can't think of a way to seal it.

I know that 600 ft/s with 15.89 gr is fine, but I can't live with a blast of air via the trigger, during the shot.



This is what was in the gun:



The rubber seems to be fine, but when I use this seal and then try to screw the valve nut on, it doesn't work. The threads of the valve nut just can't reach the threads of the cylinder.
And I am super scared of cross threading.

@45flint, as you say, spring guns are easier and more reliable lol. Pumpers can cause frustration. But, I do like working on them. And when they work, they are often great shooters. I also like the lack of recoil, and the variable power.

[oldair]

Makes a person think the original seal could have been made with a tab sticking out to close off that notch.  Among my old Sheridan parts I found a lead seal of this style, shown below. You might try making one from some kind of stiff plastic (Teflon, urethane?).  Suggest you consult with guru Lawrie for ideas.

Don R.

[Jirushi]

Hi Don R., that lead seal looks neat.
The rubber seal above (I think it is original), does have a tab to close the notch, but I cannot get it back in place.
I often have this problem with the seals between the valve nut and brass valve part.
Very difficult to screw the valve nut back on; you have to press very hard for the threads to reach each other.

Yesterday evening I cut a piece of leather in the shape of your lead seal. It didn't work.

[Goose]

That's a fascinating rifle.  Thanks for sharing it with us.

If the exhaust port is the problem, then this might be one of those situations that a carefully placed dab of silicone sealant can remedy.

Ride on,

J~

[Jirushi]

Sorry for my very late reply, Goose. That is a good idea. I will try that if this fails:



A nut on the valve retaining nut, to keep an o-ring in place.
The valve retaining nut protrudes from the hole it screws into; the o-ring will seal the air that escapes through the notch.

The valve retaining nut is 17.4 mm (outer diameter of the threads). The nut that goes on it, is 18 mm (inner diameter of the threads).
I couldn't find a 17.4 mm (or translated to inches) size nut. So it's not a very tight fit, but I hope it's strong enough. I have secured it with a bit of blue Loctite.

This is the Dremeling work: on the right is how it was before; the ring in the middle is the result. So it fits in the cylinder.



And this is how it all should go back in the gun...

[Jirushi]

The Sheridan valve stem with good quality hard polyurethane seal, doesn't seal.
The sealing surface of the brass valve part is thinner than in a Sheridan. The valve stem does work in a Sheridan.
I've been advised to seat the stem seal by hammering it.
The original valve stem works, but looks like it could do with a new seal. I will use it for now.

Fingers crossed that this plan will work!

[Jirushi]

Yes! It works!

I'm really happy. I hope my "mod" wil last.

The 18 mm nut that goes around the 17.4 retainingnut, to hold the extra o-ring in place, unscrewed when tightening the retainingnut.
Blue and red Loctite didn't work, I assume because the threads aren't making enough contact.
The solution?.........

wait for it......

Superglue!

 

It felt bad to do this, as I should have tried harder to find a 17.4 mm nut (which by the way seems to be impossible lol), but the superglue holds well. Not on the threads, just a bit on top of the retainingnut, and the top of the other nut, holding both together.

Mission completed:

[Jirushi]

There's no more air through the trigger hole of the stock, on the shot.

Now the strange part: velocity is about the same as before fixing this air loss, or even a bit less:
now doing 597 ft/s with 15.89 gr JSB on 8 easy pumps. That's 12.6 footpounds. It was 600. Well, that's 2 weeks of headaches well spent 
But it sure does feel a lot better to not feel a gust of wind when pulling the trigger!

Me likey like

[19Sheridan57]

    Congratulations ! I am glad that it is working & I hope it lasts.

[1900colt]

That's awesome you got this gun up and going... it's a very interesting one that hopefully you can find out the history of