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How can you tell it was made by a Birmingham trained barrel maker?
I'm like Wild Cattle I'll take fresh barrels over thin walls.
Jeweler;
The barrels are dovetailed lump, which is the Birmingham method of barrel construction, while chopper lump is London standard. Both methods are good methods. The chopper lump is more expensive.
You can see the two brazing lines (one on each side of the lumps) in the photo, which demonstrates that the barrels were made with a dovetailed machined into a piece of steel and that piece of steel inserted into a similar dovetailed "valley" between the two barrels, and then brazed into that valley. Afterward the piece of steel was finished machined as the lump. The lump then was finally finished by file by the gunmaker.
Bv