doublegunshop.com - home Forums General Discussion DIY Gunsmithing @ doublegunshop.com MAC SXS Shotgun - manufacture nat. d'armes de chat

That's what I first thought. I may still try that. I have lots of projects so I can take my time thinking about this one, and I can get more barrels if I screw them up. They were cheap... unless somebody buys them all.



What is the significance of that? I know about removing the zinc galvanizing on galvanized metal because zinc fumes are toxic, but what is the benefit of using conduit? Why is it better than just soldering on a fitted steel rib on the top and bottom? Remember I have a small CNC (and manual) machine shop so I can make parts, and I have mentioned I have steel on hand.

Emt

Emt is cheep thin easy to cut for the bottom rib ,the top is more difficult to make it should be hollow to save weight .english guns had the ribbe's tinned on using pure tin ,tin with lead flows a lot easier I was told the reason pure tin was used is that it expand and contracted similar to steel,used in barrels .

I didn't think the weight would be a big deal. My preferred hunters for years have rotated through full size 12ga Rem 870, Moss 500, and Win 1200 pumps. I think they are all heavier than or at least as heavy as this gun will wind up. I do have two other doubles. An old 410 (1920s likely) and a KBI O/U 12 (Russian Bakal). The KBI feels a little heavy, but the 410 is almost to light. Neither bothers me to hold all afternoon on a slow hunt.

Of course I do see the benefit of a lighter shotgun when the birds are coming fast and furious. It was brought home to me the year my son handed me his 1300 youth model and took away my 870 Express Magnum. I had been hitting well, but he had been struggling. When he took the 870s he started hitting. The 1300 came on target so fast for me the hunt was over for me almost before it began. He was hitting, but I had to stand and point because my hunt was done.

P.S. Off Topic: Having owned multiples (at different times) of those pumps I feel the 500 is generally and by far the best built of the 3, but the 1200 is my favorite to shoot.

P.P.S. Also Off Topic: I've got more then a few misc shotguns. I think the oldest is an Iver Johnson single in the project safe.

The weight savings from a hollow rib not only affects the overall weight, but also the balance.
Mike

Der Ami & MC;

When I need rib material for side x side guns and rifles I decide upon the contour of the of the rib that I want and the wall thickness and then calculate the diameter of a steel tube that has that or near that contour, (say 2 inches diameter) and then I buy (usually from eBay--although it will sometimes take a day or two to find someone selling it) seamless thin wall high strength tube lengths (say .049" wall thickness) that are scrap from the shops of automobile race car builders. I think all of the times that I have purchased these tubes it has been from some of the North Carolina race car building shops. Really nice and very thin wall "stuff".

Kindest Regards;
Stephen Howell

bushveld,
My comment applied to the top rib, do you also use thin wall tubing for them?
Mike

Yes. The size that I like is 1 -7/8 inch O.D. chrome moly alloy steel with .035 inch wall thickness.

Kindest Regards;
Stephen Howell

Interesting. I hadn't really thought weight was a huge deal. Particularly what could not be more than a couple ounces. I'll do some CAD and math later. My CAD software will give me the exact CI or CC of any solid model part. From there its simple mass X volume.

I was actually considering something more substantial on top. Functionally the equivalent of a modern raised rib. I don't have the skill to wire barrels together and regulate them like a real shotgun builder, by actually shooting them. I was thinking of just doing the layout in CAD, do little math, and set them up with blocks and fixtures so the theoretical center of the pattern should coincide at about 40 yards. Of course the machines (or myself) probably aren't capable of making the fixtures to that level of precision anyway, but... I planned to try.

Well, none of that today. I'm in the shop finishing up some custom fishing lure molds so I can get them shipped on Monday.

In theory if you bore the monobloc for the barrels so the barrels touch at the muzzles and the center of the bores are level you will be really close.