Gunsmithing cutting new chamber help

[vonbalkenbush]

After having chucked up the barrel in the lathe, is there any other way to insure the barrel is rotating true to it's centerline other than by using range rod's and dial indicators to slowly and tediously get it running to within a few .0005". Is this how all the big time chamber cutters do it? Indicate off of a range rod before the chips start flying?

-SBS

 

[Rhys]

Re: cutting new chamber help

That' pretty much it. I use a dial indicator with a long probe on it that will allow me to reach about 2" into the bore. I get that point running true, and a point just inside the bore. When these two points are both showing concentric it's time to start cutting.

 

[wnroscoe]

Re: cutting new chamber help

I've used the grizzly rod, range rods and indicators on the bore. All methods help produce tack drivers. I use range rods and routinely have rifles shoot in the .1's.

Get the barrel running as close to zero as you can and start machining.

 

[vonbalkenbush]

Re: cutting new chamber help

Didn't know if there was any other super voodo magic out there I wasn't aware of. Thanks fellas.

 

[vonbalkenbush]

Re: cutting new chamber help

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Rhys</div><div class="ubbcode-body">That' pretty much it. I use a dial indicator with a long probe on it that will allow me to reach about 2" into the bore. I get that point running true, and a point just inside the bore. When these two points are both showing concentric it's time to start cutting. </div></div>

How does a dial indicator inside the bore help? Won't the probe on the end of the indicator bounce between the lands and grooves when the barrel is rotated in the lathe?

 

[eddieharren]

Re: cutting new chamber help

"Won't the probe on the end of the indicator bounce up and down....."

I hope so. That is how you can either indicate off of the lands or, the grooves.

 

[MikeeBooshay]

Re: cutting new chamber help

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: DocEd</div><div class="ubbcode-body">"Won't the probe on the end of the indicator bounce up and down....."

I hope so. That is how you can either indicate off of the lands or, the grooves. </div></div>

Yup. Pretty easy on a 4 groove barrel, takes a little tinkering on a 3 or 5 groove. But is my preferred method also.

 

[vonbalkenbush]

Re: cutting new chamber help

Good to know. It seems to me you would get a more useful reading off of a range rod though. I guess it would depend on how long the probe on the indicator is, but I can't imagine a probe that would travel up the inside of the barrel the same amount as a range rod.

-SBS

 

[Idaho CTD]

Re: cutting new chamber help

The last barrel I did I used a range rod on the muzzle end and a dial indicator with a 2" tip on the chamber end.

 

[flounderv2]

Re: cutting new chamber help

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: SagebrushShooter</div><div class="ubbcode-body">Good to know. It seems to me you would get a more useful reading off of a range rod though. I guess it would depend on how long the probe on the indicator is, but I can't imagine a probe that would travel up the inside of the barrel the same amount as a range rod.

-SBS </div></div>

Try this..

Indicate off a range rod then remove the rod, reinsert it and see if youre still dialed in.
You'll see that it wont be which is why many indicate off the bore as its repeatable every time.

 

[Cigarcop]

Re: cutting new chamber help

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: flounderv2</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: SagebrushShooter</div><div class="ubbcode-body">Good to know. It seems to me you would get a more useful reading off of a range rod though. I guess it would depend on how long the probe on the indicator is, but I can't imagine a probe that would travel up the inside of the barrel the same amount as a range rod.

-SBS </div></div>

Try this..

Indicate off a range rod then remove the rod, reinsert it and see if youre still dialed in.
You'll see that it wont be which is why many indicate off the bore as its repeatable every time. </div></div>

I'm just curious and playing Devils Advocate...some say you won't get repeatability with the Range Rod...is this only because who's to say you installed it with the same amount of pressure as the first time, maybe in further maybe not which could throw things off??

Also getting to the Interapid with the long Stylist....what if you didn't go in as far after dialing it in would it still be dead nutz??

I'm just curious...I know there have been many accurate rifles built both ways.

 

[2156SMK]

Re: cutting new chamber help

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Cigarcop</div><div class="ubbcode-body">some say you won't get repeatability with the Range Rod...is this only because who's to say you installed it with the same amount of pressure as the first time, maybe in further maybe not which could throw things off??</div></div>

It has to do with the fact that you are crushing any burrs on the ends of the lands at the origin of the rifling and also with the fit of the pilot to the range rod and the range rod to the barrel.
If you use a loose fitting pilot on the range rod, you are not going to get a perfect alignment of the range rod to the bore.
I made up pilot fit checking rods which allow me to slide a pilot down the bore to feel it's tension while selecting a pilot.
These are basically just a rod with a 1/2" long journal and a screw at the end.
It holds a pilot so I can slide it 3" or more into a barrel and feel how tight the pilot fits.
I like the pilots to be tight enough that they will hold the weight of my 6" long checking rod when I hold the barrel with the muzzle vertical.
If the weight of the rod is enough to make the rod fall out, that pilot is not fitted tight enough for me.
Others will tell you they don't ever fit a pilot that tight.
I would ask those people how they can say that the tool is centered if there is room for the pilot to move around...

 

[Cigarcop]

Re: cutting new chamber help

Yeah I understand the problem of a loose fitting bushing but I'd like to assume were talking about a proper fitting one, in theory I would think it should stop at the same place if installed with the same pressure?? maybe not though...I guess the question there may be whats proper to one may not be to another.

 

[2156SMK]

Re: cutting new chamber help

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Cigarcop</div><div class="ubbcode-body">Yeah I understand the problem of a loose fitting bushing but I'd like to assume were talking about a proper fitting one, in theory I would think it should stop at the same place if installed with the same pressure?? maybe not though...I guess the question there may be whats proper to one may not be to another. </div></div>

To ASS-U-ME is a dangerous thing to do.

In order for everything to work PERFECT, all the pieces have to be PERFECT.
The rod has to be straight.
The bushings have to fit tightly on the rod (they don't).
The bushings have to fit tightly in the barrel.
The bushing wall thickness (concentricity) has to be PERFECT.
There are just a LOT of places for tolerances to stack up here.

There is no such thing as a perfect part if you have measuring tools with enough resolution...

Every time we have this conversation, I almost talk myself into using gordy's rods because I just don't like the idea of only being able to probe 2" into the barrel with a long indicator stem.

 

[Cigarcop]

Re: cutting new chamber help

Thanks for your take on it and the info.....still curious on the Stylist at two different locations on the bore as well.

Thanks

 

[trilogymac]

Re: cutting new chamber help

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 2156SMK</div><div class="ubbcode-body"> I just don't like the idea of only being able to probe 2" into the barrel with a long indicator stem.
Here is onethat is longer although pricy

</div></div>http://longislandindicator.com/p23.html

 

[2156SMK]

Re: cutting new chamber help

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Cigarcop</div><div class="ubbcode-body">still curious on the Stylist at two different locations on the bore as well.</div></div>

IF the barrel is straight (they are not), then the stylus measuring the GROOVE is probably the way to go.
You could also measure the top of the lands (BORE), but then you need to be asking what is more consistent, the bore or the grooves.

Again, if you have measuring tools accurate enough, you will find there is no such thing as a perfect part.

Likely, there is no difference in the results on target of a barrel dialed in to 0.0001" TIR vs. one dialed in to 0.001" TIR.

 

[2156SMK]

Re: cutting new chamber help

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: trilogymac</div><div class="ubbcode-body">Here is onethat is longer although pricy

http://longislandindicator.com/p23.html</div></div>

I know about long stylus indicators.
Show me the 0.0001" models with 2" or longer stylus on them...

Copied from your link above:

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Horizontal model 312B-15 with 2.75" long contact point. See ordering chart above or, for the vertical version see the chart below. There is no metric equivalent for this long point model and it is <span style="font-weight: bold">only available with .0005" graduations</span>.

You can request this indicator with a custom 5.5" extra long point in which case <span style="font-weight: bold">the graduations on the indicator are equal to .001"
This extra long point is not sanctioned by the manufacturer, so if you use it, all guarantees of accuracy are void.</span></div></div>

 

[Bill Larson]

Re: cutting new chamber help

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: SagebrushShooter</div><div class="ubbcode-body">After having chucked up the barrel in the lathe, is there any other way to insure the barrel is rotating true to it's centerline other than by using range rod's and dial indicators to slowly and tediously get it running to within a few .0005". Is this how all the big time chamber cutters do it? Indicate off of a range rod before the chips start flying?

-SBS </div></div>
you have to have the bore of the barrel... inline......Both the muzzle and the breech....without induceing a bend in the barrel....
bill larson

 

[excaliber]

Re: cutting new chamber help

I use a Starrett back plunge indicator. Once you get used to it, easy.

 

[2156SMK]

Re: cutting new chamber help

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bill Larson</div><div class="ubbcode-body">you have to have the bore of the barrel... inline......Both the muzzle and the breech....
bill larson </div></div>

This assumes the inside of the barrel is straight.

 

[Bill Larson]

Re: cutting new chamber help

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 2156SMK</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bill Larson</div><div class="ubbcode-body">you have to have the bore of the barrel... inline......Both the muzzle and the breech....
bill larson </div></div>

This assumes the inside of the barrel is straight. </div></div>
NO HOLE THRU THE BARREL IS STRAIGHT....
bill larson

 

[trilogymac]

Re: cutting new chamber help

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 2156SMK</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: trilogymac</div><div class="ubbcode-body">Here is onethat is longer although pricy

http://longislandindicator.com/p23.html</div></div>

I know about long stylus indicators.
Show me the 0.0001" models with 2" or longer stylus on them...

Copied from your link above:

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Horizontal model 312B-15 with 2.75" long contact point. See ordering chart above or, for the vertical version see the chart below. There is no metric equivalent for this long point model and it is <span style="font-weight: bold">only available with .0005" graduations</span>.

You can request this indicator with a custom 5.5" extra long point in which case <span style="font-weight: bold">the graduations on the indicator are equal to .001"
This extra long point is not sanctioned by the manufacturer, so if you use it, all guarantees of accuracy are void.</span></div></div> </div></div>

Sorry.... missed the .0005

 

[MarinePMI]

Re: cutting new chamber help

You know, all these jigs, rods and contraptions are fairly new (relatively speaking) to the gun smithing trade.

How about just doing it the old fashioned way?

Set up between centers.

Bore can't help but be in line...and you don't need rods and indicators to set up.

--------------------

Drive/work plate and dead center.

Tail stock with live center.

Bent lathe dog.

Steady rest.

A piece of plywood with three holes in it.

Two carriage bolts with washers and nuts.

-----------

That's it, you're done. There's been quite a few guns with chambers cut this way, loooonnngggg before gunsmiths (or anyone else for that matter) was willing to drop two bills on a chambering jig, and more $ on caliber specific rods (that aren't always as specific as they should be). As they say, there's more than one way to skin a cat (an accurately too).

Just saying...JMTCW..

 

[300sniper]

Re: cutting new chamber help

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MarinePMI</div><div class="ubbcode-body">You know, all these jigs, rods and contraptions are fairly new (relatively speaking) to the gun smithing trade.

How about just doing it the old fashioned way?

Set up between centers.

Bore can't help but be in line...and you don't need rods and indicators to set up.

--------------------

Drive/work plate and dead center.

Tail stock with live center.

Bent lathe dog.

Steady rest.

A piece of plywood with three holes in it.

Two carriage bolts with washers and nuts.

-----------

That's it, you're done. There's been quite a few guns with chambers cut this way, loooonnngggg before gunsmiths (or anyone else for that matter) was willing to drop two bills on a chambering jig, and more $ on caliber specific rods (that aren't always as specific as they should be). As they say, there's more than one way to skin a cat (an accurately too).

Just saying...JMTCW.. </div></div>


i will guarantee where the throat will be is not running concentric if you are turning between centers. will the rifle still be accurate with the barrel work done between centers? probably. is it a surefire way of achieving the absolute best accuracy? i don't think so.

 

[turbo54]

Re: cutting new chamber help

^^^and that is why indicating off the bore, where the throat will be, is in my opinion, the best method.

Ultimately, the bore ain't straight. All we can do is our best to get the bullet to enter the bore concentricly, then hope it follows the bend on its way down.

 

[eddief]

Re: cutting new chamber help

Dial in the throat and muzzle the best you can. Then select a drill bit approximately .020" smaller than the shoulder diameter of the reamer. Drill into barrel .100"-.150" short of final depth.

Then go in and dial in the throat in as perfect as you can get it. Now bore the drilled hole out to within .010" or a little less than shoulder diameter. The very rear of the bored hole needs to be stepped and opened up a .001"-.0015" bigger than the shoulder. This gives the reamer some support to get started.

Cut and thread tennon and then finish chamber to final headspace with the reamer.

If you use range rods, forget the muzzle since you are dialing in off two points on the range rod. This method is where you may have to clock the barrel if you choose.

I feel like many others, in that the throat is critical for best accuracy and many ways to skin the cat.

 

[Glen Seekins]

Re: cutting new chamber help

soooo many ways to skin this cat

allot of folks assume range rods or other rods they dial off of are all so perfect.. everything measures something to some degree. I hear some sacrifice chickens to the indicator gods..

What matters in the end is what the printout on the target looks like. The ways to get there are many and just like dad said about girls... Try them all cause they are all different

You will learn what you like best by making some chips fly..regardless of what you do, bores are not close to as straight as you would like, so no matter what its going to be out somewhere. You just get to pick that somewhere

 

[MarinePMI]

Re: cutting new chamber help

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: heatseekins</div><div class="ubbcode-body">soooo many ways to skin this cat

allot of folks assume range rods or other rods they dial off of are all so perfect.. everything measures something to some degree. I hear some sacrifice chickens to the indicator gods..

What matters in the end is what the printout on the target looks like. The ways to get there are many and just like dad said about girls... Try them all cause they are all different

You will learn what you like best by making some chips fly..regardless of what you do, bores are not close to as straight as you would like, so no matter what its going to be out somewhere. You just get to pick that somewhere </div></div>

Well said...

 

[468shot]

Re: cutting new chamber help

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: eddief</div><div class="ubbcode-body">Dial in the throat and muzzle the best you can. Then select a drill bit approximately .020" smaller than the shoulder diameter of the reamer. Drill into barrel .100"-.150" short of final depth.

Then go in and dial in the throat in as perfect as you can get it. Now bore the drilled hole out to within .010" or a little less than shoulder diameter. The very rear of the bored hole needs to be stepped and opened up a .001"-.0015" bigger than the shoulder. This gives the reamer some support to get started.

Cut and thread tennon and then finish chamber to final headspace with the reamer.

If you use range rods, forget the muzzle since you are dialing in off two points on the range rod. This method is where you may have to clock the barrel if you choose.

I feel like many others, in that the throat is critical for best accuracy and many ways to skin the cat. </div></div>

Do you use a piloted reamer when doing this? I've seen where some guys leave the pilot off when using this method.

 

[eddief]

Re: cutting new chamber help

Yes, I use a piloted reamer.