Originally Posted by
evert
Now comes the placing of the holes and the loading port..... I've left a few mm's extra at each end, and will start with milling the loading port and locating the breech mounting screw hole, so I can trim the rear end to length after those critical dimensions are established.
yes, thinking the same.... cut the loading port, and then work out from there and the transfer port/small securing screw. everything else has progressively more room for error as you work outwards, but the transfer port/barrel depth/security screw need to be just right. will cut the vertical bolt locking groove once I can assemble and make sure it gives the right amount of forwards pressure of the bolt into the barrel.
I've bored everything through now - 1/4" for the bolt, and currently 11mm for the barrel - which is too tight as you said, so I'll give it a tickle with a small boring bar. the 1/4" reamer on the bolt hole worked perfect, giving a nice sliding fit now.
Here a couple of pics showing clearances - lower is tight but fine (pretty much the same as factory) and upper has a little meat to allow for dovetails, or bolts. I really shoudl have started with some slightly larger OD bar, but this was sitting in the scrap bin 
Always looking for any cheap, interesting, knackered "project" guns. Thanks, JB.
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. In my defence, things have been a little chaotic here, though.