For many years my only infraction on the boards was a thread removed for giving the URL to an eBay auction - without the slightest intention to promote it, but more as something to avoid. So I had better not do it again.
But a couple of Chinese sellers are now offering button-rifling setups and buttons. I don't think the complete machine is worth buying, with the postage from China on what is principally just an ordinary ten ton car jack. But the buttons, which are high speed steel and titanium nitride coated, look very useful. They are meant to be self-guided, not by rotation of the operating rod.
They are flat on the ends, and meant to be pushed, not pulled as I, without the slightest experience, feel would be preferable. Being HSS, not carbide, they would lose hardness if brazed to a pulling rod, and perhaps also with any silver solder that would hold. The device holds the barrel in a collet, and I believe the intention is to stop and shift it again and again if you are rifling more than a pistol barrel. This, I feel, could cause irregularity at best, and perhaps finding the tool immobile where it has stopped.
Even doing it just the way they suggest, I would be happier using an Enerpac general-purpose cylinder, or one of the cheaper clones. they come in up to about a 15in. stroke. Or for a long pulling action, you could get an extremely long cylinder from earth moving equipment etc. Or even do it with no hydraulics at all, using the old dodge of a right-hand and a left-hand thread of slightly different pitches, to exert enormous force as one screws just a trace faster than the other unscrews.
If the bore of your barrel is one for which hydraulic seals are available, you could even have the operating rod going inside an extremely long home-made cylinder. How to avoid it buckling if it is pushed? Pure speculation again, but you could have a series of close-fitting steel collars inside the cylinder, held apart by weak coilsprings. I believe lubricants are critical in button rifling, but one suited to case sizing, such as STP oil treatment, seems likely to work.
When we consider how the top barrelmakers vie for supremacy in the field, you are unlikely to step up there any time soon. But for the restoration to life of an antique or cherished heirloom, this could be a very good deal.