doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com BSA hinge

Keith,
Thanks for the saran wrap trick, I never heard of that one before. Half/half ATF and Acetone is a very good penetrating oil, I wonder how the acetone would react with saran wrap.
Mike

On BSAs and model 21s the lumps are dovetailed and soldered. the solder joint runs right down the middle of the hook.

True, "BUT" that is a dovetailed Chopper Lump, not a dovetailed lump. On a dovetail lump the lump is all one piece & an entirely separate piece from the barrels. Inso far as I am aware chopper lump barrels have a joint in the lump whether dovetailed or not. Those which are not dovetailed are normally brazed, which I believe would likewise affect the welding.
I do know that some BSA guns had the dovetailed chopper lump, do not know if the all did or not. When just the term dovetail was used I was assuming this meant otherwise. The fact it is chopper lumped is what puts the joint in the lump, not the dovetailing.

These drawings from Burrard's "The Modern Shotgun" were scanned and posted by someone here in 2007, but the host site no longer has those images. I printed copies back then and added the handwritten notes. Scanned them again today for posting here, sorry for the weak images and text.

Jay

Jay;
Thanks for the illustrations. as can be seen in fig 4 the lump is a solid & separate piece in the dovetail lump. In fig's 7 & 8 are the two types of chopper lump barrels. The seam down the center is obvious in these. The chopper lump barrels thus, whether dovetailed or not, are the ones which could give problems with welding. I believe that when Winchester designed the model 21 they [laced the dovetail farther forward so it was necessary to increase the breeches as much as BSA did. According to Burrard this was a major complaint with the BSA in that it had very wide spaced barrels due to the dovetail.

To clear some apparent confusion. The BSA in question definitely has dovetailed CHOPPER LUMP barrels. I cannot discern even with a powerful lens whether the joint is solder or braze.

Looking at the construction I can see why the barrels are wider than "regular" chopper lumps. In the usual chopper lump joining metal is removed from the inner surfaces of the barrels, the lump sides, to bring them closer together. The braze is strong enough to form the middle layer into one solid wall which can be no thicker than the external barrel walls.

In the BSA-Mode 21 setup no metal is removed from the inner/middle layer. The same applies to monobloc barrels. The barrels must be totally round when inserted into the monobloc there is not chance to file the middle part to bring them closer together.

You have to wonder then whether the insistence on chopper lump and the dovetailed lump (the one inserted under the barrels) was to keep the gun slim and elegant, rather than stronger.

Personally I would rather opt for barrels that are a millimter or two wider at the breech ends and stronger.