opening up a tube

[TRX]

I'm scoping out what it would take to make a rifled 12-gauge barrel. The first step is the basic barrel. It needs to be .729 ID and smooth.

I'd like to avoid rifle drilling bar stock if at all possible. I may be able to acquire some thickwall 4140 seamless tube (see note), but the closest match of OD and wall thickness has a nominal ID of .625. I'd need to open up the ID by .104".

Vickery and Howe talk about roughing reamers, but they apparently cut .004 to .020", depending on the bore. It's usual to have a 3-reamer set - roughing, finishing, and burnishing, though you can burnish by other methods.

The reamers look pretty simple; there are fully dimensioned drawings in the books.

So, should I make half a dozen roughing reamers to step up to the finish reamer size, or is there a better way to do it? I was thinking about something like a piloted spade drill, perhaps.


(note) not all sizes in the steel catalogs actually exist; they're just "standard" sizes if you order enough from the mill to meet their minimum quantity.

[GeneT]

Setting aside for a minute the question of whether the DOM is suitable, I'd probably set up a boring bar between the head and tail stock and line bore to size, then burnish with a cylinder hone.

How do you plan to cut the rifling? That's a machine project of its own...

GsT

[browne]

get dom tubing 1" od x.729 id it will work on 12 ga barrels