Trying to get best info before I jump in,Which method will be easiest to learn or most accurate,running the barrel through the headstock with a cathead on the outboard spindle or holding the muzzle end in a spingle collet chuck. or 4-3 jaw chuck and shank in a steady rest, and of course center suported when threading.I know i'm opening a can of worms but I respect your opinios.

quote:

Originally posted by Mike Ray:
I know i'm opening a can of worms but I respect your opinios.

You won't after you see the bickering this starts.

like bedding, most things work .. some better than others, in the right hands.. some dont' work at all, in the wrong hands.

The most "accurate" method, provided you have enough barrel length, is running the barrel through the headstock using a spider. This method allows the best means to dial in the bore so that the threads are true. If the barrel won't reach, there are other options. But the most accurate is using the headstock when possible.

By far the simplest method, and the one almost always taught in the beginning of any gunsmithing school program, is the steady-rest method. It's accurate to within a thou or so and is MUCH faster and easier than the cathead method for most tooling setups. The steady-rest method is the one I've seen used by most general-market smiths and it appears to be perfectly adequate for almost all usages.

The cathead method can (CAN?!?!) be much more accurate and precise than the steady-rest method and is the one used by all precision- and accuracy-oriented smiths of my acquaintance.

The steady-rest method can be readily used by almost anyone with even rather crude equipment and still yield relatively fine results because of the self-correcting characteristics of the method. Good use of the cathead method however requires that the operator be able to have the work as well as the tailstock perfectly centered. Any misalignment or play in the cathead method will double the error while any misalignment in the steady-rest method will cut the error by ~80%.

2 questions for you as an individual to answer: how accurate is your equipment/ability, and how much time/resources do you want to spend to TRY to obtain the desired result?

If you're getting a new barrel for a hunting rifle then either method is fine, but the steady-rest method is NOT used by any super-accuracy Benchrest smiths.
Regards, Joe

OH, YEAH...LET THE WHIZZING BEGIN.

EVERYONE has their favorite way of doing this thing...they all work otherwise they would have changed to another method...so try them all and use the one that works for you the best...or keep ALl OF THEM in mind for when you might need a change.

All/Both ways work...BUT...before you start doing ANYTHING, MAKE SURE YOUR TAILSTOCK IS ALSO DIALED IN TO THE CENTERLINE OF THE HEADSTOCK.

You would be surprised just how many don't bother to check that little bit of minutia.

You can dial your barrel in to the "Nth" degree, but if your tailstock is out of whack either up/down or side/side you will cut an oversided chamber...and if you are workning on centers you will cut undersized/oversized/drunken threads to boot.

If I want threads a perfect as possible I use a 4 jaw and outboard cathead and dial in the BORE LINE...NOT THE OD OF THE BARREL...using a long rod(2.5") 0.0005" dial indicator or a "wiggler" to reach up inside the bore as deep as possible...BOTH ENDS...and a height gauge to set my threading toolbit height...

I only use centers when the barrel is too short to go through the headstock...then I use an extension in the chamber end and dial that in with the cat head, dial in the bore, turn a 1" section just enough for a dial in point, reverse the barrel, insert in the 4 jaw and dial in...THEN be sure the tailstock center is dialed in and cut the threads...only seldom do I use a steady rest as my cutting RPM is around 40 and I cut 0.003" per pass irregardless of calculations and the barrels are usually less than 16" and stiff.

It takes longer to describe the process than to DO the whole process.

Clean your ways and re-oil with way lube, clean the wipers on the tailstock and apron, clean/relube the cross slide threads and threading drive rod and take as much slack out of the system as you can. All this cleaning and lubing reduces "sticktion" as far as possible which will cause lots of problems in threading.

Do an online search for "threading"...there is tons of information and places to go get good information..."Practical Machinist" is one of the best sites for information on gunsmithing/threading and general machining practices.

I bought a pamphet called "Threading and Thread Cutting" somewhere along the line...a reprint from Hoyer Industries, 2002, that is one of the best reads I've found...covers all aspects for the most part including all the formulas for calculating the required data and I bought many machining books at Half.Com.

THEN PRACTICE, PRACTICE, PRACTICE...on a piece of 1 to 1 1/2" 41XX steel...just set it up, dial it in, turn it slightly and start cutting threads of every pitch on a 1-2" long section...keep turning off those threads off and recut threads on that new dia.

After using up a 12" piece steel you will know how to cut threads. Use a carbide insert tool...I use the cheapest LARGEST SIZE too that will fit my tool post.(12x36" lathe, 200 size toolpost).

This is all about developing muscle memory, mental imagery, proper cycling, eye/hand coordination and reflexs...do it slow and you won't break too many toolbits or your machine.

Threadin is very simple once you get over your "fear of flying"...nothing but proper, accurate setups...doesn't matter if you are threading a barrel or cutting a 4-48 screw...that's what a lathe is...a "SCREWING MACHINE".

Luck

quote:

Originally posted by J.D.Steele:
By far the simplest method, and the one almost always taught in the beginning of any gunsmithing school program, is the steady-rest method. It's accurate to within a thou or so and is MUCH faster and easier than the cathead method for most tooling setups.

How do you set the barrel up for threading in a steady rest?

I have done it both ways and even though between centers and steady rest is the fastest setup I prefer the through the headstock method. It is much more rigid and threads cut better. I have a small pump to pump my cutting fluid through the barrel and this flushes chips out. Chambering goes much faster this way and you have to be careful not to get carried away. I still take reamer out every .060 or so to make sure all chips are flushed. My headstock is too long for most barrels so I made an extension for the barrels so I can indicate them in and have a place to hook up my pumping system. I use lead between the jaws and barrel to give it a little anglular movement and also lets me know I'm not putting a bending pressure on the barrel.

quote:

Originally posted by Westpac:
How do you set the barrel up for threading in a steady rest?

I always thread between centers, always, even when I'm gonna set it up in the headstock later. Reason? No collet setup therefore some work travel sometimes under threading feed pressure.
Regards, Joe

quote:

Originally posted by srose:
I still take reamer out every .060 or so to make sure all chips are flushed.

Me too.
Regards, Joe

Thanks guys i'm in the process of leveling my new to me old lathe (clausing colchester 13 x 40) and I need all the info I can get Thanks again . I realize nothing replaces experience and no short cuts when learning something complicated.

quote:

Originally posted by J.D.Steele:

quote:

Originally posted by Westpac:
How do you set the barrel up for threading in a steady rest?

I always thread between centers, always, even when I'm gonna set it up in the headstock later. Reason? No collet setup therefore some work travel sometimes under threading feed pressure.
Regards, Joe

Sure, threading between centers I understand, however you said you use the "steady-rest method" and I'm not quite sure how that works.

As far as preparing both ends of the barrel for centers, a person can't just lop then ends off, face 'em and expect the bore to be running true to the bore. You can be off several thousandths that way, so, how do you prepare the end of the barrel for the tail stock center so that it is square to the bore? And do you change your set up between threading and chambering? I'm mostly curious.

A question from a dummy, well at least a non machinist non gunsmith. What the hell is a cathead?? I understand what a spider is and how the barrel is threaded / chambered. Ive seen that done. But what is a cathead?

I think people are calling the spider a cathead but not sure.

Cathead = spider.

I always first indicate on the bore line spud and then cut the center angle, then break the setup and thread between centers. Yes it's more work but doing it this way ensures even thread spacing since I've found that the barrel will sometimes slip longitudinally in my headstock under threading feed pressure.

I ALWAYS thread between centers and then usually but not always chamber in the steady-rest.

Not the 'best' way nor the fastest way but like so many other things around a shop, it's my way (grin).

You guys with sophisticated tooling are fortunate, I hafta 'make do' with what I can afford. My opinions and advice are based largely upon my own experience of the simplest way to achieve good results.
Regards, Joe

Having done it both ways, I would always chamber through the headstock with a 4 jaw and a spider if I could. Unfortunately, I have a compromise lathe (small enough to get into my basement, but quick change gears and can turn 36" between centers) that has a small headstock. I have to chamber and crown with the steadyrest. That's a real PITA on heavy, long octagon barrels! I set it up as true as I can get it using a wiggler bar between the bore and tailstock, and then use a floating reamer holder. Acceptable results, but maybe could get better through the headstock.

dave

The cat head method does not deliver the accuracy most people think it does.
You can dial in the bore on that end but the bore is often crooked which defeats the indicator work.
I can make the process work either way. If the lathe is large enough I would just as soon use a steady rest.
You can dial in the bore and turn a short section at the muzzle concentric and then chuck on it. The chamber end is turned concentric with the bore on that end.

No matter which method is used if the bore is a little crooked you will never get it perfect even with both ends dialed in.

quote:

Originally posted by SR4759:
The cat head method does not deliver the accuracy most people think it does.
You can dial in the bore on that end but the bore is often crooked which defeats the indicator work.
I can make the process work either way. If the lathe is large enough I would just as soon use a steady rest.
You can dial in the bore and turn a short section at the muzzle concentric and then chuck on it. The chamber end is turned concentric with the bore on that end.

No matter which method is used if the bore is a little crooked you will never get it perfect even with both ends dialed in.

I don't think you quite understand the purpose of the cathead/spider. It isn't used to dial in the bore on that end, it is used to help bring the bore into alignment on the chamber end. The critical end where the reamers pilot will run.

Here is a YouTube video of Gordy Gritters using the PT&G Grizzly Rods to dial in the chamber end. He only measures the first 2 inches, I dial in that area where the pilot will be at the end of the job. Just beyond the throat. The object is to give the bullet a straight shot into the bore, just past the throat. Once the bullet is in the bore, it is on it's own.

http://www.youtube.com/watch?v=aII2tbavKnM

You have already aligned and leveled your lathe, right? And not with a carpenters level. I was in someone elses shop, we were looking at his lathe, I put my hand on the headstock and bent over to look at his toolpost, the lathe rocked. All of the feet were not even touching the floor!

quote:

Originally posted by Westpac:

quote:

Originally posted by SR4759:
The cat head method does not deliver the accuracy most people think it does.
You can dial in the bore on that end but the bore is often crooked which defeats the indicator work.
I can make the process work either way. If the lathe is large enough I would just as soon use a steady rest.
You can dial in the bore and turn a short section at the muzzle concentric and then chuck on it. The chamber end is turned concentric with the bore on that end.

No matter which method is used if the bore is a little crooked you will never get it perfect even with both ends dialed in.

I don't think you quite understand the purpose of the cathead/spider. It isn't used to dial in the bore on that end, it is used to help bring the bore into alignment on the chamber end. The critical end where the reamers pilot will run.

Here is a YouTube video of Gordy Gritters using the PT&G Grizzly Rods to dial in the chamber end. He only measures the first 2 inches, I dial in that area where the pilot will be at the end of the job. Just beyond the throat. The object is to give the bullet a straight shot into the bore, just past the throat. Once the bullet is in the bore, it is on it's own.

http://www.youtube.com/watch?v=aII2tbavKnM

Which is why working between centers with a steady rest is nowhere near as good as using a indicating rod (Range rod as they call them)
You will never get the entire length of the bore dialed in. It's not straight and doesn't have to be. As stated above once the bullet is in the bore it's on it's own.

What is accomplished here is the axis that the bullet starts out on (camber Axis) is as close to perfect alignment as possible to the bore where the throat is and may be just a little bit past that area. The bullet needs to be aligned in both the "concentric axis" and in "cylindricity"

What this means is the bullet is centered on the bore as best as possible and not out of angular alignment from end to end of the chamber.
This gives the best possible transition from free bore to rifling possible and upsets the bullets path the least. and again once it's in the bore there is nothing more you can do.
That is why it doesn't matter where the muzzle reads on an indicator.

Ray,Imo, Good advice from Wespac on the youtube vid. Im not a gunsmith but am a skilled turner who has threaded hundreds of rifle barrels to fit most models of sound moderators. I could not believe by how much the rifling runs off(is not straight or concentric) to the outside diameter of the barrel. So what the T.I.R. is, at the barrel end, will not necessarly be the same where the lands will start a couple of inches deeper.

A great deal of skill required for this type of work.If not sure have a gunsmith do it,or try out your skills on an old barrel on your new Lathe. Like most of us, machines have there idiosyncrasies,its best to get to know them first. Good luck and keep us posted.jc

My tailstock is used to push my reamer. I do not chuck my reamer in it. You may get your tailstock indicated, but is your chuck that close? Below is my reamer holder and flat pusher that goes in the tailstock. I want it to push and not direct the reamer.

Only in the headstock and I use a cathead on both sides of my headstock. I can chamber short barrels that way with my Clausing. Remember if you chamber with a chuck, put copper wire or something to keep from bending the barrel during setup.I drill and taper bore before chambering.
Butch

As you can see, Mike, there are almost as many ways of doing this as there are people DOING it.

EVERY method has it limitations and accuracy concerns and set up requirements.

Some barrels are centerless ground to shape and the bore can be a long way off center to the barrel OD...some of the better quality ones are ground on centers on CNC equipmen nowadays, kept cool and the OD and bore centerline are almost perfectly concentric and parallel.

By carefully studying these replies, the "problem areas" have been revealed and some solutions presented.

Many of the problems can be addressed by just using proper machining techniques...remember, what you want to do is nothing more than a simple turning operation requiring simple well known actions...like keeping things cool so the "pipe" doesn't grow in length and circumference...light cuts to keep the temp down, using coolant/lub and so forth.

Doing close chamber/threading requires close attention to detail, a LARGE helping of study and investigation and questioning of just what it is you are doing...it's NOT JUST A MECHANICAL PROCESS without a large amount of deep thought to what it is you actually want to accomplish.

Plus learning/knowing your machine, quantifying the measurements on the various moveable parts...THEN QUALIFYING those measurements so you can correct where applicable.

I was lucky in having excellent, old time machinists that took a bit of extra time now and then to give me "secret" knowledge, that you can find scattered all over the net...fairly prevelent if you just look, but with an open mind. It doesn't matter if your lathe is old or a brand new CNC machine...the basic principles still apply at the lowest levels.

I might be able to set-up my headstock/cathead in a relatively short time, but to get the tailstock to cooperate is a whole 'nuther story.

I've been tempted to use the toolholder to hold the reamer as somewhere along the line I read of one 'smith doing so using a floating reamer holder and getting just as accurate a chamber as using all the other methods, but that presents other problems of centering and maintaining very small tolerances...probably not doable with my knockoff lathe. Someday when I hit the Lotto and ca afford a really precise CNC lathe I might just do that.

Luck

Foobar,
I have been in several of the top custon barrel makers shops. They do not use a centerless grinder or CNC grinders. They are contoured by CNC lathes. Some of them polish them better than others. They can't make the OD concentric to the bore or if they could the barrel would look like a snake.
Butch

quote:

Which is why working between centers with a steady rest is nowhere near as good as using a indicating rod (Range rod as they call them)

The range rod has to have some clearance to get it in and out of the bore. You are assuming that your alignment is perfect based on a rod that has some clearance.

quote:

Originally posted by butchlambert:
Foobar,
I have been in several of the top custon barrel makers shops. They do not use a centerless grinder or CNC grinders. They are contoured by CNC lathes. Some of them polish them better than others. They can't make the OD concentric to the bore or if they could the barrel would look like a snake.
Butch

I read in a magazine review (probably Precision Shooting) that John Krieger turns his barrels first and then bores/rifles them. The Bill Webb barrelmaking video shows Bill's machine boring a long blank and coming out within a very few thousandths. However Bill also emphasizes that his machine is very slow compared to normal barrelmaking machines.

I know from experience that the barrels I've cut off have had the boreline far, far from the OD at various distances from the ends, but these were production barrels for the most part.
Regards, Joe

JD, you are correct on the Kreigers and Bartlein does the same.
SR, an indicating rod with a bushing needs about .0002 clearance to slide into the bore and about .0002 to slide on the indicating rod. It seems to me that it would make it off possibly .0002. I don't use one. I have a very slimbody Mitutoyo 513-504 indicator. It has a short .375 length probe. I first indicate the breech end with a Deltronic pin. I have them in .0001 increments for ea. caliber. Ea. set has 25 pins in .0001 increments. Say your doing a 6MM, most have an approx .237 bore size. My set has a mean of .237 and 12 on either side for a range of .2358-.2382. After indicating it till a tenth indicator doesn't move with the spindle bearings warm and checked with it turning slow in back gear I go to the next step. I predrill with a drill about .050 smaller than the shoulder diameter and about .100 short. I then stick my long reach indicator in the drilled area and indicate the area that will be just in front of the throat. I am indicating the grooves and it allows me to check if a land is taller than one of the others. I have some short solid carbide boring bars. I taper bore the chamber to make sure that it is coaxial to the lathe bearings. I finish up the job with my chamber reamer. I want my reamer to follow my taper bored hole and not influenced by a tight bushing on the reamer or some type of reamer holder.
This is my way and works for me. If you have done a lot of chambering over the years you will change and modify your methods as you go.
Butch

Tenth reading dial indicators similar to the ones Butch uses to dail in the barrel and to “dial in the grooves”.

quote:

Originally posted by butchlambert:
I then stick my long reach indicator in the drilled area and indicate the area that will be just in front of the throat. I am indicating the grooves and it allows me to check if a land is taller than one of the others.

Do you see many of these? I would think one wouldn't have to worry about such things when using quality, hand lapped, air gauged barrels with guaranteed uniformity to within .0001 over the entire bore. In which case I would think indicating off the lands would be sufficient for all applications.

True, true, Butch...in todays world...not necessarily so in the past. I've come across a few well known barrels that had up to 0.015" difference between one side and the other...this was back in the 60's...makes for strange groups as the barrel heats up and wiggles around...and causes all kinds of head scratching and hair loss as to the why's and wherefores.

So far all the barrels, even the "cheapy's" I've aquired/used over the past 10 years or so were very close, but I still get a few thou variation when I turn for concentricity to set up a muzzle brake or need concentricity for centering in a 4 jaw.

Maybe some of the variation came from polishing...or...??

Things have changed quite a bit in the last little while.

Hey...I got a couple of those "long pecker" thingydoodle indicators...pricey little devils aren't they...for a hobby wannabee...I've paid a lot less for a good shooing rifle, but they are well worth it at twice the price when it comes to making money off them.

You want to measure a realy bad barrel, do a bad shooting NEF...oblong holes, variable height bore/grooves and no rifling at all in some sections...makes you appreciate just how good barrel and barrel making has become and just how much you get for the relatively cheap price, compared to "yesteryear".

Luck

quote:

Originally posted by FOOBAR:
wherefores.

Hey...I got a couple of those "long pecker" thingydoodle indicators...pricey little devils aren't they...for a hobby wannabee...I've paid a lot less for a good shooing rifle, but they are well worth it at twice the price when it comes to making money off them.

Buy the best and cry once!!!

quote:

Originally posted by SR4759:

quote:

Which is why working between centers with a steady rest is nowhere near as good as using a indicating rod (Range rod as they call them)

The range rod has to have some clearance to get it in and out of the bore. You are assuming that your alignment is perfect based on a rod that has some clearance.

And so do guage pins but you don't here anyone disputing that.

The thing is you take into consideration the "clearance" and add that to your run out.
All you need for clearance is .0005" anyway.
I'd like to see someone indicate a barrel closer then that. out side of the benchrest community

quote:

The thing is you take into consideration the "clearance" and add that to your run out.
All you need for clearance is .0005" anyway.
I'd like to see someone indicate a barrel closer then that. out side of the benchrest community

I would not count on the clearance being on center. As you rotate your barrel gravity and the pressure from an indicator can make the pin wiggle.
But your statement about .0005 does not hold water since there are many people that dial work to closer tolerances on a daily basis.

As far as using a gauge pin goes, if the bore is reasonable straight just turn the muzzle concentric with the bore. If you chuck on the muzzle the relatively great length to diameter ratio of the barrel will provide good alignment in a steady rest. Just study the trigonometry a few minutes.

quote:

Originally posted by SR4759:

quote:

The thing is you take into consideration the "clearance" and add that to your run out.
All you need for clearance is .0005" anyway.
I'd like to see someone indicate a barrel closer then that. out side of the benchrest community

I would not count on the clearance being on center. As you rotate your barrel gravity and the pressure from an indicator can make the pin wiggle.
But your statement about .0005 does not hold water since there are many people that dial work to closer tolerances on a daily basis.

As far as using a gauge pin goes, if the bore is reasonable straight just turn the muzzle concentric with the bore. If you chuck on the muzzle the relatively great length to diameter ratio of the barrel will provide good alignment in a steady rest. Just study the trigonometry a few minutes.

I didn't say anything about dialing in other materials closer. We are talking Barrels here.
Yes gravity and the pressure from the indicator can make the pin wiggle but that is added to the total run out and is accepted as "it is what it is"
Not to mention if you roll an indicator over it will not read the same either. that is what a coaxial indicator is for.
Then there's the tolerance and repeatability of the indicator in question. Did you know that most Tenth indicators are only good to +/-.0002" and repeat with in +/-.0001" Just because it say .0001" on the dial don't make it so.
Cosine error??? Granted we are talking comparator reading but still.

The other thing is you said "reasonably straight bore" Ok how would you measure that?? (I know you it's done I'm asking you) Then the question is why?

SR4759 your philosophy on using a steady rest is fine and correct with a few considerations.
One unless your tail stock is dead nuts perfect, you can set up a steady rest to be completely out off the axis that is driving it. Again using a good indicated in tail stock is the only proper way to set up the steady rest. But even then incorrect pressure on the tail stock can influence the run out.

I'm not going to say your method is incorrect or inaccurate.

But for rifle barrels that have a bore that wanders from center line of the OD all you really need to align is the first .200 of bore past the throat and even that may be over kill.
What i'm are getting at is if the bore is a snake and is running out from one end to the other (as deep hole usually are) then indicating in both ends is useless when it may be so far out in the middle of the barrel (Why would it matter?)

Take a barrel for example with a bow in the bore and say for this discussion it's off center by .010" in the center of the length.

Now If I set it up in the lathe using a spider on the headstock and a four jaw chuck, I indicate the bore using a very close fitting range rod.
Now you take the same barrel on the same machine and indicate in the bore on the muzzle turn a small length to be concentric to the bore. And we'll say for this discussion that it's so close that the indicator can't tell if there is any run out. Then you remove the barrel and set it up between centers and in a steady rest.
Get everything dialed in and running true.
Explain to me how with a bow of .010" in the bore on center of the barrel. How can that set up be anymore accurate then just indicating say the first three inches of barrel??
If there is a bow or some other malformity of the bore in relation to the OD What would it matter. The bullet's path would not be affected
And you would actually be introducing the bullet to the lands at an angle Because you would be essentially at the edge of the chord ( Yes I know trig too)
Think about it.
Now granted your method takes the run out and splits the difference. But the Range rod method introduces the bullet to the land and grooves as concentric as possible with out getting into super expensive and time consuming setups.
The Steady rest method is fine for tube, pipe or shafting that is concentric to the OD. But we all know a rifle barrel's bore is not concentric to the OD at least not less then a few thousandths. And again I'd like to see the Gunsmith that had a barrel UT'ed to measure the wall thickness to the half thousandth.

SR4759 I'm not doubting you, Your technique, or your ability. Just that in this perticular case it's over kill and will not result in a more accurate rifle.
Now a prop shaft, a linear bearing slide or something similar You bet it better be between centers with a steady rest.

Absolutely WoodHunter!!!!! Problem is, those little boogers with such a high degree of measurement accuracy can have you chasing your tail because of 1000 times more measurable slop in bearings and gears...or roughness in the grooves.

The fact that chambers get cut by many methods and still perform to the level they do, pretty much proves that NO ONE WAY is the best...we all learn how to do things more than one way, but stick to the way that fits us and our equipment the best, for the most part.

It is one thing to fiddlephart around as a hobbyist trying one way then another...and a completely different kettle of fish if your bacon depends on your methods...I did things one way when I was flatrating jobs, another way when I was getting paid by the hour...and stil other ways when I was piece working.

I THINK AND BELIEVE that it is the first few inches of the muzzle and crown, the concentricity of the chamber, the first few inches beyond the chamber AND the ammo reloaded to as close to perfection as possible, that gives a rifle the highest accuracy possible...what is going on in the middle section(as long as it isn't WAY out of whack) is of lessor importance...

Even then if the amount and direction of the "bow" is known, it can be adjusted to TDC or BDC which can be adjusted for with the sights...this has been done at least once that I know of...I was there when it was being done and I shot most of the target work.

I've "recycled" several shot out barrels by cutting off the "worn out" section in front of the chamber...just as many benchresters/targeters do today...rechambering and installing on different actions and ended up with a barrel that miraculously turned back into a shooter...this is how I learned about the wall thickness difference...actual measurment with a tubing mike.

I turned the barrel uniformly using very light cuts. It's now stuffed into an NEF swithch barrel platform with a 6BR chamber and it shoots .2-.3's with 55-70 gr bullets for about 20 rounds or so...just like the barrel did as a 6-284 for 3-4 rounds, before it started walking the shots up and left.

I've had barrels that the rifling was almost totally absent for 8-10" just beyond the chamber that continued to shoot relatively good groups...considering...this isn't anything new, but it does point out that maybe some cherished beliefs need to be reconsidered...or not...your choice.

So whether or not a barrel is concentric ID/OD to the nearest "NTH" might not mean much...until barrels CAN be cut/ground to such perfection, we will never know for certain...we only have our own thoughts and conjecture/proofs...WITHOUT EMPERICAL PROOF...that an 5 bucks will buy you a cup of coffee whatever, at Starbucks.

Besides there is quite a bit of difference between a spinning shaft that can be balanced dymanically over a fairly wide speed range and a stationary rifle barrel. This whole question DOESN'T boil down to a few specifics on barrel setup in the lathe.

About all we can do is do the setup and cutting/installation, using the best method we know how to use and that has proven effective and let the shooter do his/her part at their end.

All the different posts, as usual, give excellent, tasty food for thought.

Luck