Indexing a barrel

Z

Zebra13

Member
Gentlemen,

I have a friend who wants me to rechamber a factory .222 Magnum barrel to .223 Remington. He also would like it done so the factory front sight sits top-dead center, and the barrel markings are orientated correctly. It would seem there is a way to figure this all out on paper, and make it happen on the lathe. If so, how? Or is it a cut and try approach? Any help would be appreciated.

Thanks,
Justin
 
If it is a factory barrel, he would be a fool to mess it up. If the reamer would clean up the old chamber no indexing would be necessary. If he has to shorten it a little, he will have to index it. I believe on a 16TPI barrel you would be screwing in the barrel at the rate of .o625 per turn. If he is a quarter off he will need to cut either .0156 or .0781 off depending on which side of vertical that you are on. Does that confuse you? It does me.
Butch
 
Justin,

I've done this a few times, and you can get an "exact" number to cut back by the method Butch says. I have found it a little tricky to get things done perfectly by cutting the whole amount off in one whack. I find it better to use the rule of halves and cut the barrel and shoulder back by increments to avoid cutting too much off. Sometimes touching off the work can remove a couple thousanths, and surface finish also comes into play a bit ( I used a file the other day to remove a slight burr as i approached my zero point, and while I didn't ruin anything, it reduced my crush a bit). So, I usually lock the carriage in place, make trial cut noting my dials on the cross slide, mark how much that equated to radially by trial fitting the action, then take another cut, etc. until I know how the work is progressing. Leave about 1/8 to 3/16" for crush as you approach the full index point.

Scott
 
I made bushing to screw an 1894 30-30 barrel into a 91/30 action with no reamer and got it to headspace and got the sight dovetails top dead center.

I would tell you how, but it would spoil the fun of you figuring it out.
 
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