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Beuchat SR850 Pneumatic – Rebuild, O-Ring Sizes, Oil & Parts Compatibility

jackal

New Member
Sep 4, 2026
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I’m new to this forum and spearfishing and I am rebuilding a Beuchat SR850. The older SR550 thread here was very helpful.

I’m attaching a scanned copy of the original SR850 manual and exploded parts diagram so the part numbers below are easy to follow and hopefully useful to anyone else working on one of these guns.

My SR850 is essentially new and unused but has been sitting for about 30 years. It will pressurize and shoot, but it leaks from the front. When submerged, I can see bubbles coming through the holes in A4, the Brake Chamber. I removed A1 through A4, then A7, the Opening, and removed A5, the O-Ring Pressure Washer, and A6, the Barrel Opening O-Ring. A6 is visibly flattened from age and appears to be at least one likely source of the leak.

From the earlier SR550 thread, my understanding is that after completely depressurizing the gun and removing B17/B19, the Trigger and Trigger Pin, and B20, the Safety, the front assembly can be loosened and A9, the Barrel, tapped rearward inside A10, the Air-Chamber, allowing the barrel and piston to be removed for inspection and resealing.

All help is appreciated, particularly any information on fork oil brand and quantity for the SR850, how to determine O-ring sizes, compatible replacement seals, etc.

Cheers!

Carlos
 

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