Indicating Barrels to chamber

[rickhirsch]

iv'e been rebarreling guns for about 15 years and some them have been outstanding most have been sub 1/2 moa
guns. I use the mike bryan method using pins both ends of the barrel to achieved .0001 run out then drill and bore
I run the reamer usually get .0002 to .0005 when the bore is done. question is do you guys pins or indicating rods .
I went to gun smith with friend he has cnc he uses rods and some the other gun smiths use them too.
if you have a cnc its nice because you can rough the chamber perfect. this guy builds winding benchrest guns
again the question is witch one is better. they both work . thanks guys

 

[DaveTooley]

Here we go again.
I use CNC and pin the muzzle and indicate in the throat.

 

[Dusty Stevens]

 

[tonyb]

Here we go again.
I use CNC and pin the muzzle and indicate in the throat.

Hey Dave, what is the advantage of using a pin in the muzzle instead of indicating that area too?
Thanks,

Tony.

 

[DaveTooley]

Hey Dave, what is the advantage of using a pin in the muzzle instead of indicating that area too?
Thanks,

Tony.

I indicate on the pin.

 

[tonyb]

I indicate on the pin.

I guess I should have made myself more clear, what is the advantage of using a pin over indicating off of the lands?
Thank you.

 

[clowdis]

I do it the same way Dave does. I've tried other methods but they just didn't make me feel good about having the bore running straight. That includes the famous method of putting a long rod in the breech end and double indicating it.

 

[clowdis]

I guess I should have made myself more clear, what is the advantage of using a pin over indicating off of the lands?
Thank you.

Tony,
With the muzzle end of the barrel sticking way out the end of the lathe, sometimes it's easier to set up an indicator on a pin than it is to get it up on a level where you can get the stem into the barrel.

 

[tonyb]

Tony,
With the muzzle end of the barrel sticking way out the end of the lathe, sometimes it's easier to set up an indicator on a pin than it is to get it up on a level where you can get the stem into the barrel.

Thank you.

 

[DaveTooley]

I guess I should have made myself more clear, what is the advantage of using a pin over indicating off of the lands?
Thank you.

The only advantage is it saves time. While barrels are very very good these days nothing is perfect. So you can spend a lot of time fiddling with things that get lost in the noise. A 27" blank and it's dialed in to less than 5 tenths on the pin in the muzzle. Dialing it in to 2 tenths on the lands is a waste of time. I dial the throat to a few tenths, rough with a core drill that acts like a single point tool in a CNC and I have a true hole for the finish reamer to follow. It's a simple process.

 

[DR_2297]

So to be clear, you are saying that your alignment of the bore is indicating one spot (the throat) and the pin sticking out of the muzzle - which then creates an axis. Rather than indicating two spots over a distance at the breech end with no regard as to where the muzzle end is (flopping around in space - exaggerated of course).

 

[6fatrat]

I use rods at both ends.
Indicating off the lands assumes uniform run out when it is rifled.
Steve Bair

 

[DaveTooley]

So to be clear, you are saying that your alignment of the bore is indicating one spot (the throat) and the pin sticking out of the muzzle - which then creates an axis. Rather than indicating two spots over a distance at the breech end with no regard as to where the muzzle end is (flopping around in space - exaggerated of course).

Yes

 

[DR_2297]

For those who are indicating in one point at the throat are you setting your pivot point in the chuck (or whatever work holding method you are using) at the throat / indicating point?

 

[DaveTooley]

For those who are indicating in one point at the throat are you setting your pivot point in the chuck (or whatever work holding method you are using) at the throat / indicating point?

No I choke up on it as much as possible for rigidity. Aligned is aligned regardless of where to hold it.

 

[jelrod1]

Start Straight and leave straight. Check your work. How you get there will vary wildly depending on your lathe, setup, and experience. I believe If you achieve those things, along with solid fundamentals and machining practices it will rarely be your fault a gun won't shoot.

I use a long stem indicator at the throat and a pin at the muzzle as my baseline setup. Rarely with modern barrels do I have to change much if any. I do check at the throat and beyond as far as I can though and that allows me to catch an outlier if it comes through and adjust accordingly.

 

[Lucky Shooter]

I'm convinced that many of us-----including myself----tend to
spend too much time chasing the "1 tenth" accuracy goal and
wind up settling for "the best I could do".

How much deviation in this is acceptable for a barrel to be used
in serious BR competition ? Maybe we amateurs should use this
as a standard.

A. Weldy

 

[rickhirsch]

well thank you guys for the imput . seems like most of us do the same method with a little
variance. I'm am a machinist by trade . I just don't want to get stuck doing things the same old
way . I'm old but I still want to do things the best way. and when I saw a top gun smith using the
double indicating rod on his cnc it made me wonder ? when I was shooting short range benchrest
years ago . the gunsmiths I new were indicating the bore's in .0001 but they would drill a pilot hole
maybe .020 under and then put the reamer in and finish the chamber runout was about .0007 to
.001 and those ppc's were winning at local matches and national matches too. thanks buddys

 

[SBLH10]

Years ago Winning agg's where .2700/.2500 not the top 20 plus teen's agg's we are seeing today.

Chet

 

[rickhirsch]

I haven't shot short range benchrest in years so things have changed. the competitions
some shoot in the teens I never saw a .250 agg win.