Pre-Drill & Boring A Chamber

[GeneT]

Gene, If I drill, indicate the throat, and bore to my indication at the throat, don't I have 2 points indicated?

That's a great question Butch, and I've reversed my thoughts on it a couple of times as I sit here pondering it. My answer above, was really addressing the Gordy method vs chambering between centers (or the equivalent vis a vis indicating both ends). On one hand, your chamber should definitely be axially aligned with where you indicated, but I'm not as certain that it guarantees lineal alignment with the start of the bore. If the barrel was tilted, with the axis of tilt right at the spot you indicated, then when you bore a chamber, the chamber would be linear with the indicated point, but might the point not necessarily be linear with the start of the rifling? If the bore was way out of alignment, you'd 'see' that because you'd be indicating an oval cross-section, but a practical misalignment probably wouldn't be noticeable. Does that make sense? Am I missing something?

At the end of the day if you can stick a borescope in there and see that the leade is uniform across all the lands you've probably done all you can with respect to alignment.

Regards,

GsT

Edit: Butch, in re-reading what you wrote, I may have misunderstood entirely. Did you mean indicate the throat and the bore or indicate the throat and then perform a boring operation? (I initially interpreted it as the latter, but am now unsure.)

[Louis.J]

I want to thank everyone for taking the time to share their individual means and methods it is highly appreciated on my behalf.

[Butch Lambert]

That's a great question Butch, and I've reversed my thoughts on it a couple of times as I sit here pondering it. My answer above, was really addressing the Gordy method vs chambering between centers (or the equivalent vis a vis indicating both ends). On one hand, your chamber should definitely be axially aligned with where you indicated, but I'm not as certain that it guarantees lineal alignment with the start of the bore. If the barrel was tilted, with the axis of tilt right at the spot you indicated, then when you bore a chamber, the chamber would be linear with the indicated point, but might the point not necessarily be linear with the start of the rifling? If the bore was way out of alignment, you'd 'see' that because you'd be indicating an oval cross-section, but a practical misalignment probably wouldn't be noticeable. Does that make sense? Am I missing something?

At the end of the day if you can stick a borescope in there and see that the leade is uniform across all the lands you've probably done all you can with respect to alignment.

Regards,

GsT

Edit: Butch, in re-reading what you wrote, I may have misunderstood entirely. Did you mean indicate the throat and the bore or indicate the throat and then perform a boring operation? (I initially interpreted it as the latter, but am now unsure.)

Gene, let's start again. I use Deltronic pins to indicate muzzle and breach. I am in the headstock with a cathead on both ends. I do warm up my headstock bearings before final indication. I predrill and reach in with my Mitutoyo indicator and indicate the throat. I taper bore to the indicated throat. I want my reamer to follow my prebored hole and not be influenced by a bushing beyond the throat.
Gene, If a barrel has a bore that makes a RH or other turn beyond that, it should have been scrapped. A Gordy rod cannot straighten a wandering bore.
I can take the time to do this as I only do my own work. Most of this .0001" stuff is BS anyway! Remember the thickness of a brown human hair is about .003"

[alinwa]

yeahh.... but ain't nobody ever measured using the term "take off just a BHH"

[GeneT]

Gene, let's start again. I use Deltronic pins to indicate muzzle and breach. I am in the headstock with a cathead on both ends. I do warm up my headstock bearings before final indication. I predrill and reach in with my Mitutoyo indicator and indicate the throat. I taper bore to the indicated throat. I want my reamer to follow my prebored hole and not be influenced by a bushing beyond the throat.
Gene, If a barrel has a bore that makes a RH or other turn beyond that, it should have been scrapped. A Gordy rod cannot straighten a wandering bore.
I can take the time to do this as I only do my own work. Most of this .0001" stuff is BS anyway! Remember the thickness of a brown human hair is about .003"

Thanks for the clarification Butch. Yes, you have two points dialed in. In theory the advantage of the Gordy method is that you're dialing in the first bit (let's say an inch) of the bore, rather than end-to-end. Bores *do* wander - of that much I'm certain. If you look at commercial gunn drilling machines it seems the common boast is no more than 0.004" from true in 36" (an odd figure, but I think 36" might be the capacity of the tool). So, if the bore wanders 0.004" from truly straight the _in theory_ aligning the bullet with the first little bit of the bore makes sense (whether it makes a practical difference or not is another matter). But there are lots of valid questions: does that tiny deviation from straight actually have an effect on anything? Does the Gordy method actually compensate for it? The answers of course are "I don't know". IMO, there are just too many variables in putting shots on target to definitively say. So, a related question is: do you think the Gordy method hurts?

GsT

[Butch Lambert]

Thanks for the clarification Butch. Yes, you have two points dialed in. In theory the advantage of the Gordy method is that you're dialing in the first bit (let's say an inch) of the bore, rather than end-to-end. Bores *do* wander - of that much I'm certain. If you look at commercial gunn drilling machines it seems the common boast is no more than 0.004" from true in 36" (an odd figure, but I think 36" might be the capacity of the tool). So, if the bore wanders 0.004" from truly straight the _in theory_ aligning the bullet with the first little bit of the bore makes sense (whether it makes a practical difference or not is another matter). But there are lots of valid questions: does that tiny deviation from straight actually have an effect on anything? Does the Gordy method actually compensate for it? The answers of course are "I don't know". IMO, there are just too many variables in putting shots on target to definitively say. So, a related question is: do you think the Gordy method hurts?

GsT

Yes, I think it causes more problems. Why have a muzzle flopping around? Sure you can index it, but why? On the wandering bore, do you know that it is a flat elipse, an elipse in a radial path, Is it a straight bore starting at the beginning at one end of the barrel and in a perfectly straight line, exiting .004" off center at the other end?
.004" in a 36" barrel would be about .00011" in 1" wouldn't it. Gene, I can't see .00011" from an undetermined path being a problem.
It is a fun thing to talk about on a cold rainy day.

[jackie schmidt]

Basic machine shop practice dictates that you can always indicate two spots dead true. It is only when you add the requirement of establishing a third spot true with these two spots does the problem of straightness, or the lack of, come into play.

By keeping the muzzle true at all times and truing the chamber end in a spot the the bullet “sees” the instant it enters the lands, then single point rough boring the chamber, (that’s the third point), can you insure that the chamber is as true with the barrel and the barrel is pointing straight.

This method does require predrilling the chamber so you can reach in with an appropriate indicator to the spot you intend to true up.

I can change barrels with the confidence that the bullet impact will be within a couple of inches of the one I just took off. While this does not have anything to do with the accuracy potential of the barrel, it does do away with the need for any indexing.

Of course, if the ID’s of barrels were truly straight, all of this would be a moot point.

[GeneT]

It is a fun thing to talk about on a cold rainy day.

Yes, and that's how I perceive this thread. I very much value considered input from others. Thanks for lots of food for thought Butch!

GsT

[Rubicon Prec.]

RE: methods that allow muzzles to be “flopping around” in the lathe.

How many people that use this method time the muzzle to TDC? How many people that think they are timing it to TDC have ever verified that it remains at TDC once removed from dual slider/chucks? Has anyone marked the high spot, removed their fresh cut and timed barrel, stuck a piece of stock in the lathe, faced and ID threaded it to match the tenon, then screwed their timed barrel into this female thread and verified your muzzle runout high spot is still the same as it was before?

[alinwa]

RE: methods that allow muzzles to be “flopping around” in the lathe.

How many people that use this method time the muzzle to TDC? How many people that think they are timing it to TDC have ever verified that it remains at TDC once removed from dual slider/chucks? Has anyone marked the high slot, removed their fresh cut and timed barrel, stuck a piece of stock in the lathe, faced and ID threaded it to match the tenon, then screwed their timed barrel into this female thread and verified your muzzle runout high spot is still the same as it was before?

FWIW I have.... and much more

How many people that use this method time the muzzle to TDC?

I have, but generally don't except that recently I've started doing it again..... currently I'm trying BR rifles this way as it drives the rifle down into the bags, or at least doesn't allow them to lift as much. On a F-Class, hunting or other bipod setup I use some iteration of "down" (never straight down) as it causes the muzzle to lift.

[QUOTE=Rubicon Prec.;830833] How many people that think they are timing it to TDC have ever verified that it remains at TDC once removed from dual slider/chucks? /QUOTE]

I do, I used to do it every install. Any more I trust it enough that my feedback from recoil is enough to verify.

Has anyone marked the high slot, removed their fresh cut and timed barrel, stuck a piece of stock in the lathe, faced and ID threaded it to match the tenon, then screwed their timed barrel into this female thread and verified your muzzle runout high spot is still the same as it was before?

I can't see any reason to do this. But for my glue-ins I have tenons made up specifically to pre-set my timing so that the new barrel indexes where I want it.

As far as "is it repeatable"...... I once went through a pile of 7 blanks and threw them lightly into the lathe and pre-marked them.

Yes, it's completely repeatable, else it wouldn't be much use to me (I get it.... your contention is "you're fooling yourself"... so be it) I have barrels that have been on and off dozens of times, the only "problem" is that over time, using the torque specs I use, they tend to advance.... I've ordered quite a few 1.350 shanks because of this. Currently I'm playing with nutting. Because of this.

I've cut down and re-threaded barrels as many as 5 times just changing out throats and/or chambers.

I've taken old barrels, for instance I've redone 8 barrels from .243AI because I have no use for the chambering. In each case I "Gordie'd" them first, in some cases I screwed'em on and shot 'em, marked the scope settings and then redid them as something useful to me and see where they useta' point VS new. I've Gordied a barrel, took it out and hacked off the tenon (or cut it off in the lathe but in any case it has to be reset) and stuck it back in for the new chamber and ended up with the marks still relevant........In all cases I Gordie'd them just because putting a barrel on will-nilly bothers me. Wasting barrel with a picky gun, a gun that messes sideways every time, a gun that teases but don't pleases is just frustrating to me.

I've rechambered and clocked barrels through the hours of the clock. Shot the circle.

What Gordie Gritters came up with IMO is a way to map out a usefull 4"-5" section of the barrel, but maybe more importantly a way to actually INDICATE the center deeper in than an indicator probe can reach. It's nothing more than an indicator extension, a very useful one.

And yes..... when I'm all done and I can reach I will often run a test indicator in and verify the grooves. All I've learned from this is that the old "grooves and lands can be eccentric from each other" is a played out hand. I sometimes wonder if some of the prior "testing" was done in the lapping bell


To repeat, the Gordie rod, properly used is a useful tool for reaching in further than can be accomplished any other way.

In My Opinion.

HOW it's used, and how the findings are put to use is personal preference. I ain't sellin' nuttin'.... but having more than once found 2 thou runout in less than a 5" section of bore I sure ain't leaving that card on the table!

Also, I work a lot with lighter per length and longer contours than "normal" to typical BR as it's denoted here.... Frankly most 20"-24" 6MM and 30 barrels have less than 5 thou of wobble at the muzzle after being mapped. But I have worked with hunting rifles, especially fluted (and yes, I use only factory fluting and those done by FeldKamp hissownself) hunting rifles which show great runout. I had a rifle once, blank fluted by Kampfeld Kustoms which shot 16moa from center done between centers! Luckily it still shot to standard, it was clocked almost straight down. I had to lap the Talley rings to bring the scope nearer to optical center.

I once took a wildly bent 28" 30cal blank (It was 8moa off between centers).... ran it through the clock for group size and shape with a known load.

And no, barrels aren't "banana'd" IMO but they're something not straight. And since I've been playing with nutting and I'm not averse to wasting a few cases, I've swung a lot of barrels thru the 15-20 degrees I like to work with in an attempt to find a "real" up-and-down at or near what my mapping shows me. I even sometimes will hand-cut the chamber a few thou at a time..... A guy can start with a whole bunch of bolt-face clearance and rechamber-reset through a long way before the barrel touches the bolt when using a nut.......

but in the end, I don't really know exactly how the barrel is helixed.

Hence my new giggle... the "3D Tuner"

Get 'er close and tune the rest.....

"GOT's ta' get that clean vertickle!!"


LOL

[Rubicon Prec.]

I can't see any reason to do this.

If you don’t do that, how do you verify what was high in your lathe, is really the non supported high? You mention a typical .005” of muzzle runout: it doesn’t take much to move a 20” 1-1/4” bar .005” if held at one end. I do think, and this is my opinion, most people are fooling themselves thinking their setup is stress free, and will repeat if held the same way it is in the real world, from one end:

I have, but generally don't except that recently I've started doing it again..... currently I'm trying BR rifles this way as it drives the rifle down into the bags, or at least doesn't allow them to lift as much. On a F-Class, hunting or other bipod setup I use some iteration of "down" (never straight down) as it causes the muzzle to lift.

Frankly most 20"-24" 6MM and 30 barrels have less than 5 thou of wobble at the muzzle after being mapped.

Are you saying you can tell the difference how the rifle rides the bags between a muzzle .005” TDC vs one timed .005” BDC? That’s pretty impressive.

Edit: for the record, I’m not crapping on the Gordy method, or any method. But I see lots of claims of runout that can’t be proved. I think a lot of people read on the internet about the “best way” to do things, and never take the time to prove their work. If they did, they may find they could do things much faster, have barrels that will usually zero within an inch after having the stock, scope and barrel removed and replaced, and still have the same result on target. Or maybe they will find the internet is right.

Edit #2: The grizzly rod is an extremely handy tool, if you understand the inherent errors. I don’t use the Gordy method, but I do use similar tooling as part of my setup.

[alinwa]

If you don’t do that, how do you verify what was high in your lathe, is really the non supported high? You mention a typical .005” of muzzle runout: it doesn’t take much to move a 20” 1-1/4” bar .005” if held at one end. I do think, and this is my opinion, most people are fooling themselves thinking their setup is stress free, and will repeat if held the same way it is in the real world, from one end:

Are you saying you can tell the difference how the rifle rides the bags between a muzzle .005” TDC vs one timed .005” BDC? That’s pretty impressive.

Edit: for the record, I’m not crapping on the Gordy method, or any method. But I see lots of claims of runout that can’t be proved. I think a lot of people read on the internet about the “best way” to do things, and never take the time to prove their work. If they did, they may find they could do things much faster, have barrels that will usually zero within an inch after having the stock, scope and barrel removed and replaced, and still have the same result on target. Or maybe they will find the internet is right.

Edit #2: The grizzly rod is an extremely handy tool, if you understand the inherent errors. I don’t use the Gordy method, but I do use similar tooling as part of my setup.

NO, I'm NOT saying ".005 is typical" for BR blanks..... in fact I said the exact opposite.

But I have built hunting rifles many times with runout of over 20thou that easily met my .250moa agg'ing spec.

If you don’t do that, how do you verify what was high in your lathe,

Are you saying that you think there may be 5 thou of sag thru the headstock? From chuck to cat'shead? I'm just super confused here by your confusion....And as to "supported only on one end"..... I can't imagine where you got that from.


Or are you talking droop once installed? You don't know how to measure barrel droop? Just stick a dial indicator on it and friggin LIFT with your finger! One indicator on the tip of the barrel, another on the forend tip of the stock..... voilahhhh


I set the barrel thru the headstock pivoting it on the point where I set the leade. This means I've got 10 inches of barrel I can take measurements in. 6 good inches. I don't attempt to "verify it" by adding another step nor by making another tool, it's perty simple with the indicator in place anywhere in the first 6 inches of the barrel other than the leade area I can easily see deflection from something as simple as pushing with my fingers, and jacking my working section into stress-free neutral is child's play.

"How do I know it's neutral?"

"Because I check it all thru setup"

It's funny.... up to this point everyone I've actually spent time with as they diss on Gordies method, I find out in the end that they're doing something entirely different and just calling it "Gordie's Method"

I see lots of claims of runout that can’t be proved.

True.... This is true of ANYTHING. The Scientific Method requires as it's most basic tenet "repeatable results"... If the experimenter can't reproduce under scrutiny, if the scientist can't structure, apply, control and document repeatedly under conditions of "scientific rigor".... He ain't got a case. I've spent my life and some serious dinero on setting up for this scientific rigor. And, having it, I tend to call people out.....why do you think I've got bets out on the internet for all to see? Like "You think bullets "go to sleep?" "Well I got a thousand bucks says I will SHOW you they don't!" Or more to the point..... "I'll buy your airfare, pay all your expenses to get you here to shoot over a series of targets which will PROVE whether or not your groups are shrinking. SAME day, SAME everything.... SAME BULLETS GOING INTO THE SAME GROUPS at different distances...." And when you show bullets going to sleep, fairly, openly, scientifically, I'll pay up like a slot machine. And we'll plaster said groupages all over the innernet and more importantly you will be RIGHT, and I'll not only be wrong.... but I'll have learned something.

I have the ability to shoot groups over 2 Oehler 43's recording groups at 3 points along the trajectory of any group. If that's not "proof" enough then please point me to the error of my ways


Why do you think I've got a challenge on this forum right now that "$1000.00 says NO, I DO NOT believe all gunsmith's are created equal, nor are all methods equal. I DO NOT think you can hack together a gun using the same components as me and beat me" but if you're up to it, let's go!"

You use the term "unprovable".... or "can't be proved".

Please tell me of just ONE of these things and I'll make an attempt to structure a test which will (hopefully) make you agree that things ARE provable and testable.

AND..... that 99.9% of the time method beats money. In 'Rifle Accuracy Facts' Vaughn often employs "the old engineer's trick" of exacerbating problems to see if they ARE problems. Harold was well aware that formulating a method of checking stuff can be hard.

But very little in this world is "unprovable" or untestable. What I've learned is that people are too bloody LAZY to test with rigor

Hence my bets.

Maybe MONEY will induce people to put up or shut up

so far, no takers....


Maybe I'll videotape my "Gordie setup" to show easily how I absolutely KNOW it's stress-free....'cause I walk it around like a friggin' GEArshift.....is why.....


LOL

[Rubicon Prec.]

Lots of words. If f you’re videoing something, do what I mentioned above without edit. Set up, chamber, time your barrel how you choose. Mark the muzzle TDC while in the lathe. Remove the barrel, toss some stock in the lathe, face, bore and ID thread it to match your barrel. While it’s still in the chuck, thread your barrel into it, place a DTI on the muzzle, spin the chuck and prove that your TDC mark is still TDC. It is repeatable, right?

Can you set up your barrel, chamber, document the muzzle runout, throat runout and breech end runout, then remove the barrel from the lathe, and duplicate ALL the previous numbers? I’m not saying it won’t happen, but I’m not going to make that claim.

[alinwa]

Lots of words. If f you’re videoing something, do what I mentioned above without edit. Set up, chamber, time your barrel how you choose. Mark the muzzle TDC while in the lathe. Remove the barrel, toss some stock in the lathe, face, bore and ID thread it to match your barrel. While it’s still in the chuck, thread your barrel into it, place a DTI on the muzzle, spin the chuck and prove that your TDC mark is still TDC. It is repeatable, right?

Can you set up your barrel, chamber, document the muzzle runout, throat runout and breech end runout, then remove the barrel from the lathe, and duplicate ALL the previous numbers? I’m not saying it won’t happen, but I’m not going to make that claim.

OK, why this fiddling about with making a fake action face? That's not "repeating" that's just checking for something else entirely.


But that aside.... since it DOES in fact go on the gun, and it will be indexed as such, why isn't is relevant if I take the barrel out, COVER ALL THE MARKS, or better yet, pull a barrel out of the pile that was marked 4yrs ago.... put 'er back into setup from square one and see if it repeats?

[Rubicon Prec.]

And while we’re LOLing “I set the barrel thru the headstock pivoting it on the point where I set the leade. This means I've got 10 inches of barrel I can take measurements in. 6 good inches. I don't attempt to "verify it" ”
I’m going to LOL at claims of getting “good” runout measurements 6” into the bore. And at 10”.....