Hi Jeff.
Though I've never done a breech bolt conversion on Mercury jaws I had a look at what's involved and a measure up of everything to see how difficult a job it would be.
Basically all you need is a HW35/80/90 breech bolt and nut, a 7mm ream and a tap the same thread pitch as the Weihrauch bolt, the Mercury breech bolt is 0.25" (6.35mm) OD, the HW35 type bolt is 7mm, the base of the Weihrauch breech bolt threads is 0.243".
The way I'd do it is to ream the left hand breech jaw and the barrel block out to 7mm --- these are originally 0.25" (6.35mm) so you're only opening the hole by 0.65mm.
Once you've opened the left hand fork out to 7mm I'd poke the tap in from that side to tap out the right hand fork --- this would effectively use the left hand fork as a guide to ensure the tap goes squarely through the right hand side.
One more thing you may have to look at is the machined flat in the top of the breech bolt, this could need deepening by 0.325mm (half of the 0.65mm increase in bolt diameter), this could simply be done with a Dremmel if it needed it.
Without the lock washers the HW35 type bolt and nut are spot on the right size for the job and would end up looking like the one that Johnbaz has shown.
All the best Mick
Originally Posted by T 20
Hi Jeff.
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