Buy a Viper barrel vice. Sinclair's sells them. PM me your email address and I will put you on contact with the guy that makes them and you can buy direct.
Where can a guy get a decent barrel vise these days, having a hard time finding one on this side of the border???
If you have a friend with a lathe, one can be made. I've used this one for years. 1 1/2" barstock, 1 1/2" diameter split aluminum sleeves. I've made a variety of them to match various barrels. Clamping bolts are 7/8".
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5 of them on EE as we type
https://www.canadiangunnutz.com/for...fle-magazines-reamers-other-gunsmithing-tools
I made and sold a few barrel vises like this one. Stopped, because material cost, shop time and delivery (heavy) resulted in a higher price than I thought they were worth.
When making the hole for the sleeve, clamp the blocks together with a spacer, then drill and bore to size.
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Wheeler Engineering Universal Barrel Clamp Works great and can accommodate a variety of barrel sizes. You still need a vice.