Problems cutting, threading, and recrowning a barrel.

[Benmuncie]

A barrel crown and lands at the end of the barrel really do matter. I cut a 308 barrel down to 18 1/4” and used an annular cutting jig to rethread the barrel. After I finished crowning, I took the rifle out and shot it. Cold bore shots were dead on, but as I continued shooting the bullets would drift left.
After messing with different bullet weights and powder charges I finally discovered that I had messed up the lands at the end of the barrel because I used the bore guide wrong on the annular cutter.
I swapped barrels to a barrel I know is good and I’m back to consistent groups.


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[Balljoint]

Unless you are an owner of a gun lathe and know how to use it let a good gun smith do it for you

[tobnpr]

You're conflating different operations.
A piloted annular cutter, followed by a similarly piloted threading die can deliver "acceptable" results for such things as slant brakes on AK's where it's not possible to remove the barrel nor a traditional lathe operation (been there, done that). I'd never use one where very tight tolerances are needed.

Crowning is different tooling. You need an 11 degree, or flat piloted reamer. What did you use?

The problem with annular cutter pilots is two-fold, they're solid- and don't come in half-thou sizes at minimum to get a precise fit in the bore; one that's too tight will score/damage the lands, too loose will result in chatter, threads that aren't concentric to the bore.

Crowning "by hand" can be done with the correct tooling, Manson offers a couple of kits that will do this.

[mikeinco]

educations cost money, how much did this cost, and what did you learn ?
crown angle can be anything. most of my rifles a FLAT.

[big honkin jeep]

I've cut and crowned with a hacksaw, a file and a round headed brass screw with lapping compound chucked up in a drill, I've also crowned with a Lee case length gauge and cutter. Never any problem with the results.

[mikeinco]

i guess all lathe makers and gunsmith should quit.....
or
we don't all have the same quality standards.

I've cut and crowned with a hacksaw, a file and a round headed brass screw with lapping compound chucked up in a drill, I've also crowned with a Lee case length gauge and cutter. Never any problem with the results.