Indicating a barrel for muzzle break threading on my lathe

[375 CHEYTAC]

I am curious about the various different techniques used for indicating a barrel when cutting threads on a lathe for muzzle brakes. Most gunsmiths do this for
+/- $100. How I have been doing it so far is, separate the barrel from the action. Then run the barrel through the headstock, and using a mini chuck/spider, I indicate both ends of the barrel off of the bore to better than .0005 on each end(on the chambered end I instal a PTG indicator rod and indicate off that). I mostly work on Remingtons, which require my big action wrench to get them apart, this also requires removing the scope and rings and bases. Not the easiest way to make a hundred bucks. Its not so bad when you are installing a new barrel because its not on the rifle yet. Is this method over kill, This method has been producing bench rest quality chambers when chambering. Any Gunsmiths out there willing to share some of there years of experience.
I would appreciate any and all opinions. I hope my description of my process makes sense.
Cheers
Trevor

 

[Hired Gun]

Welcome to LRH,
Since you are doing other peoples guns for money you must be licensed and by very definition a gunsmith. We welcome your sharing of your experience as well. This is by far the friendliest board on the net thanks to the excellent members and level headed moderators. It also has some of the most knowledgable smiths participating.

Gordy Gritters showed us this method while studying under him in MO. Unless the end of the barrel you are working on is already perfectly true and concentric your range rods will only magnify any burrs or out of round, high or low lands present. Means when your indicator is reading zero runout you may actually have around .001" to .003" runout and worse the farther in you go. A long tip indicator or a Grizzly style rod is a much more reliable/repeatable means of getting your bore aligned. On the chamber end if you are using a floating reamer holder getting perfect means little as your reamer is following the bore anyway. This may or may not show up as runout in the finished chamber. To get the most out of a aligned bore you need to drill and singlepoint the bulk of the chamber to get the initial part of the chamber in line with your throat. We indicate at the throat and 2" farther as my alignment part of the bore. This gets the chamber aligned with the first 2" of bore as good as is possible. Is this necessary for fine accuracy? Clearly not but it makes me feel better so this is how we do it. Our chambers indicate dead nuts no runout as measured with .0001" Starret indicators and bore scope inspections reflect very square engagement with the rifling.

For a muzzle brake we use both the Grizzly rod and indicaters to get right at the crown and then 2" farther to align the crown and the brake.

This method along with our barrel qualification process has yielded extremely consistant results.

Shawn

 

[orwapitihunter]

I do quite a bit of threading of muzzles for suppressors and muzzle brakes. I run the barrel through the headstock like you do, but then I use a long tipped indicator to dial in just at the muzzle. I dial in the deepest point I can reach with the indicator and a point just inside the muzzle. When both of these are running <.0002" I start cutting. Prior to that I will dial both to about a half thou. and then run the lathe and warm the bearings before the final indicating. When cutting I stop a bit short of my major diam. and recheck that the bore is still running true. Then finish to major and thread.

 

[375 CHEYTAC]

With the amount of success I have had with chambering using the same style set up as Richard Franklin and Mike Bryant (as well as numerous other gunsmiths across North America). I don't feel a change in my system is going to increase accuracy. The only time I would use an indicator rod of any style is when going through an existing chamber. I have watched Gordy Gritters video several times and always wondered if people were having much success with that method, This is definitely a change in the topic from muzzle brake threading, but an intersting change at that.
I am going to try the method Orwapiti hunter mentioned for muzzle brake threads. If you can mount a suppressor and have that running true, I think that says a lot.
Thanks for your help, from both respondents. As previously mentioned I am a newbie to this forum and it definitely seems like a great bunch of guys.
Cheers

 

[bigngreen]

I do it through the head stock but don't remove the action, I have a drill chuck set up in a tool post holder and slap the appropriate Gordy rod in it and dial in then barrel. Thread and fit brake then crown. I have had to do one that was short and I made a tool that goes into the action then I chuck it up and hold the muzzle in a steady rest. Not ideal but if I had to do many short one's I would make a steady rest with a cats head built into it. Takes me about an 1.5 hours from start to finish.

 

[orwapitihunter]

Biggreen,
I do my long chambers like you just described. A Gordy style rod with the appropriate bushing, all held and positioned by the tailstock. But for threading at the muzzle I just indicate off the bore with the tip of my dial indicator.
As a side note, if you are indicating the barrel and cutting threads, now is a good time to recrown.
Don't forget to mention that to the customer.