Machining an AR15 barrel from a barrel blank

[dsdmmat]

Figure I would put this here for all those who want to know how it is done.

Building (machining) an AR-15/M16 M4 barrel from a blank

When I left the Marines in the mid-90s I got a job working the gun counter at a small sporting goods store. We only stocked one AR-15 rifle at a time. Back then, it would be hard to imagine how c…

rifleshooter.com

 

[repete]

I wondered how to set up for the gas port, never thought of using an upper DOH!

 

[tony]

There's a couple of things with this machining process that caught my attention. Maybe they are important to some and maybe not but they would be important to me...

Holding a shaft in a 4 jaw chuck does not mean it is running true for the parts length, in fact they rarely do. Even running with the barrel in a steel collet is no guarantee, although it is likely to be better.

First, with the barrel held in a four jaw and indicating the range rod we have no idea what the other end of the barrel is doing runout wise. If the barrel protrudes from the back of the headstock the barrel at that end should be held in a "spider" and the bore indicated there as well. The purpose/benefit of this is getting everything in the same plane and concentric as much as possible.

Another option would be to make sure the outside diameter of the muzzle end is concentric with the bore by turning a small spot. Now you can chuck up and indicate the spot and know the bore at that end is running true. The barrel near the chamber end would run in a "cathead" and steady rest. You would now indicate the bore there and all should be good.

There are many ways to skin a cat, some are not as messy as others...