G150 Compass for L42A1 sniper CES

[Nigel]

I picked up a couple of G150 Prismatic compasses (British military) that would form part of the CES for the L42A1 sniper rifle. Unfortunately one of them is missing the Prism and thumb ring assembly. Does anyone have any spares or know where I could find the Prism assembly?
Thanks

Information

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[Peter Laidler]

EBay. Zillions of spares there. But the parts are very much hand fitted and the threads are very fine. So be very careful. With that bubble it'll be useless

[browningautorifle]

With that bubble it'll be useless

I was thinking it had been scrapped and parts stripped for that reason.

[Eddie Parks]

Over the years I have refurbished dozen of these compasses. In point of fact the bubble trap should cope with that bubble. Just try rotating it gently and it should disappear. Refilling the compass is in ant case not beyond the ability of an amateur. The spares are all available from the makers, google Francis Baker - Ive always found them very helpful.

[Charlie303]

Just try rotating it gently and it should disappear.

Can you explain this a bit more? Just rotate what? The compass? I don't think I get it...

Thanks.

[Eddie Parks]

Can you explain this a bit more? Just rotate what? The compass? I don't think I get it...

Thanks.

Hold the compass flat with the glass uppermost and the lid open and facing away from you. Then slowly rotate it through 360deg around the long axis still keeping it flat. The bubble will should then be trapped in a groove that runs unseen around the inside of the bowl. It will of course pop out again when you put the compass down.

Alternative method. Open the compass lid, place the whole thing on your palm face up lid pointing away. Rotate your hand palm down and then slowly bring in back to palm up. Practice makes perfect.

Very simple to do, very difficult to explain without a diagram.

As Peter has said refilling the bowl is relatively simple, full immersion is best, but I've achieved it using a syringe and a lot of patience. You can (or could) get replacement seals from the Francis Baker.

[Peter Laidler]

Point taken re the bubble trap but the bubble is still there - and it shouldn't be! The bubble trap is a palliative and not a cure. Refilling a compass is quite simple, I agree - if you have a bowl of isoprophyl alcohol or another suitable damping fluid (with a low refractive index but I wouldn't worry about that unless you're crossing a desert) and a new filler screw seal. That's the easy bit. The difficult bit is establishing why it leaked in the first place and fixing that. That's normally the glass seal(s) that have failed. And de-gassing the damping fluid afterwards. If you don't de-gas, then another bubble follows as sure as god made little green apples.

But that said, once serviceable they last for ever and a day. Good, solid, reliable and accurate. I taught my son to map read in open country with one

[browningautorifle]

Here's more about it if you haven't been there yet, worth the read. https://www.milsurps.com/content.php...-Peter-Laidler)

Hope this diagram comes through so it can be read, the names of parts is helpful to discussion... Run pointer arrow across picture and click on the box and arrow at picture bottom.

[Peter Laidler]

That was nice to read again. Thanks Jim

[browningautorifle]

Very informative how to Peter. For the novice with imagination, could be done...