looking thru the bore after its dialed in for chambering

[NesikaChad]

Once upon a time an old man smarter than smart ran a batch of barrels that looked like chord wood once he was done. A big ol messy pile.

We threaded and chambered a dozen of them and then got up at 3am and hung a lantern on the tgt and started shooting from 600 yards.

The best group won.

This is how you test a barrel.

Crooked, straight, lopsided, whatever. What difference does it really make as long as the hole in the paper is small?

There's no crystal ball here, it's patience and diligent application of fundamentals and testing. 20+ years ago the setup/tennon prep/chambering process was largely done between centers on a steady rest. Are barrels really shooting that much better now with the use of range rods, indicators, and lord knows what else?

If they are and barrel making hasn't changed all that much then it suggests to me this is where the focus of attention needs to be applied.

I personally don't care if the muzzle runs out an inch. If I time it to the vertical plane and do my part they seem to shoot well, maybe even borderline exceptional sometimes.

FWIW Tammy Forester was on the 92 Atlanta team. She had a squib and missed it. Stuffed another one in behind it and turned the middle portion of her rimfire barrel into a 25 caliber.

That gun still holds national records fired after the "oops."

You just never know till you shoot it.

C

 

[alinwa]

There's no crystal ball here, it's Are barrels really shooting that much better now with the use of range rods, indicators, and lord knows what else?


C

ummm, welll, guns that were competitive ten yrs ago aren't today. And the cutting edge groups of the 80's wouldn't get your name called at a modern match.

al

 

[4Mesh]

Now I'm confused

You say you're with Wayne but also that you don't believe barrels are ever crooked? I think Wayne has seen crooked.

No, I am saying, like Wayne, that errors are small and few (paraphrasing what he said there). If he advocates things like your next paragraph, then ok, I stand corrected, I no longer agree with Wayne.

Regarding runout at the muzzle.....NO it is NOT always in the 8-10thou range. The muzzle on the outboard end may be running out 100 or 200 thou... and it ain't just sporter barrels. 600yd and 1000yd BR barrels are bad too.

It is the statements like this that I disqualify automatically Al. Listen, If you have one of these chucked up your way and it's in a best-case for the first 6", but is out 200 at the muzzle, on a 30" barrel, you do realize that means there is an AVERAGE of .0083 error PER INCH for the rest of it? You do realize that if you are dealing with a 30 cal barrel, you can look in one end of it and from certain vantage points, could not see all of the other side due to the curve? Easily you should be able to see when viewing down one side, that the exit isn't visible. All you can see is the "hump" in the middle. I have been saying for some time, these figures are grossly exaggerated, and that it is due to measuring errors. Thanks tho for confirming that it wasn't my reading comprehension or lack thereof, having me misunderstand what was being said.

I am quite surprised actually, to see Jackie, with all his years of machining and process experience, saying that it is the gun drilling process that is to blame for these errors. Paraphrasing of course, calling on the part about everything else follows that hole, etc etc etc. I have no doubt that after cutting a barrel apart, you can see if there was a "crooked" bore. (I won't intentionally use the wrong term there cause I think very few got the humor anyhow.) What I can't understand is thinking it happened in the gun drill process and that everything after, including od turning, left that hole alone.

Whatever...

BTW I agree with you that when one has .001 to .003 clearance around the base of the bullet one will have .0005 to .0015 of unavoidable inbore cant.

Your math assumes that the base of the bullet is in the throat. It is not. Therefore, the inbore cant could be quite a bit more (of course, it may be less and that's all voodoo in there).

I ALSO agree that the absolute best way to find the throat area ((whether you then "straighten or not)) is with a direct indicator reading. I do wonder though why some of you don't back the indicator off and check
the rear.

I can't check it Al, it's already in the chip pan. I drill mine in an engine lathe with no indication done before it ever goes in the lathe where it is chambered. Why would I bother to indicate that part of the bore when the barrel manufacturer has already said to remove it? (Yes, they say remove from the muzzle, but, they mean, remove that which was/may have been affected adversely by the lapping process. Which really means both ends. They don't tell you to remove the first inch of the chamber end cause they fig'r you'll get that part on yer own without them say'n so.)

On this note, for a long chamber like Sarver's Hulk how would a person actually find the throat without using some Rube Goldberg setup like Gordy's method?

Drill out the rough hole and use an indicator that fits.

I will say that IMO boring and then chambering this straight section of bore results in the tightest most repeatable chambers I've ever seen.

I am confused as to why, mechanically, that would be the case? I should think they would be just as repeatable if you began with a piece of bar stock. I don't see what that hole has to do with the work.

I think we all agree that the important thing is to center the throat/leade area to the centerline of the lathe for chambering.

100% agreed.
[/QUOTE]Regarding the "in an inspection environment" contention. In my limited experience the every day fact is that you use the best method possible. You can't do any better than that. IMO Gordy's method is the best method possible for generating usable data 4-6" up into the bore.

al[/QUOTE]Opinions vary. It's a good thing they do or the forum would be pretty boring.

Phil.

 

[alinwa]

No, I am saying, like Wayne, that errors are small and few (paraphrasing what he said there). If he advocates things like your next paragraph, then ok, I stand corrected, I no longer agree with Wayne.
It is the statements like this that I disqualify automatically Al. Listen, If you have one of these chucked up your way and it's in a best-case for the first 6", but is out 200 at the muzzle, on a 30" barrel, you do realize that means there is an AVERAGE of .0083 error PER INCH for the rest of it? You do realize that if you are dealing with a 30 cal barrel, you can look in one end of it and from certain vantage points, could not see all of the other side due to the curve? Easily you should be able to see when viewing down one side, that the exit isn't visible. All you can see is the "hump" in the middle. I have been saying for some time, these figures are grossly exaggerated, and that it is due to measuring errors. Thanks tho for confirming that it wasn't my reading comprehension or lack thereof, having me misunderstand what was being said.

I am quite surprised actually, to see Jackie, with all his years of machining and process experience, saying that it is the gun drilling process that is to blame for these errors. Paraphrasing of course, calling on the part about everything else follows that hole, etc etc etc. I have no doubt that after cutting a barrel apart, you can see if there was a "crooked" bore. (I won't intentionally use the wrong term there cause I think very few got the humor anyhow.) What I can't understand is thinking it happened in the gun drill process and that everything after, including od turning, left that hole alone.

Whatever...
Your math assumes that the base of the bullet is in the throat. It is not. Therefore, the inbore cant could be quite a bit more (of course, it may be less and that's all voodoo in there).

I can't check it Al, it's already in the chip pan. I drill mine in an engine lathe with no indication done before it ever goes in the lathe where it is chambered. Why would I bother to indicate that part of the bore when the barrel manufacturer has already said to remove it? (Yes, they say remove from the muzzle, but, they mean, remove that which was/may have been affected adversely by the lapping process. Which really means both ends. They don't tell you to remove the first inch of the chamber end cause they fig'r you'll get that part on yer own without them say'n so.)

Drill out the rough hole and use an indicator that fits.
I am confused as to why, mechanically, that would be the case? I should think they would be just as repeatable if you began with a piece of bar stock. I don't see what that hole has to do with the work.

100% agreed.

OK Phil....

First of all, The runout at the muzzle is "doubled" when you look at it. Even though the barrel tends one direction it goes UP and DOWN equally from centerline. .100 of lope is only .050 of curve.

Second of all, I'll back down on my .100-.200 figures. I'm going out on a limb there, extrapolating data anecdotally. Speaking of this though. run the numbers on how crooked a barrel must be to shoot 14" off at 100yds when chambered between centers. I've heard of barrels running out well into the first decimal place but I'd better check my notes before quoting figures. I know that it sure looks huge when you turn the rig on.

My math doesn't "assume the bullet's in the throat," not sure where this is going but my math is based on .000 to .100 freebore and bullet seated to the neck/shoulder junction. It's being guided by the neck of the case up to the last .100 of engravement at most.

I know you can't check it, and you can't even find the throat until you've got a couple oz of chips out of your way.

All of my figures are taking the lapping bell into account.





Now regarding the repeatability of the chambering method.

I learned to chamber setting up between centers and reaming the whole bloody thang using a "roughing reamer" and a "finishing reamer" and chambers varied wildly in width. Some I even swear were ovoid in cross section but that was almost 30yrs ago. And nobody knew why. Piloted reamers were a sometimes thing.

Then I heard about pre-drilling and boring, mebbeso ten yrs ago..... and about how some people once they got in (got the chips out of the way) would find that the throat wasn't in the middle any more. And what to do about it???? Some would re-indicate using the muzzle and the new bore and try to clean up the lopey chamber hoping it WOULD clean up before running out of room.... Some would just engage. I've seen it stated right here on this board within the last 6mo that as long as the pilot will get into the hole, "have at it!" "It'll find center!"

Now I see why chambers vary in width and why some reamers "cut on one flute.......

Then I watched Gordy do one and as he got down to where all the problems start (got the chips cleared) he reached in with a long stem indicator and BINGO, there was the throat, right where the Gordy rod predicted.

And the chamber was running true, dead centered on that hole.

And the reamer touched down like a feather settling on the lake.....

And I said hmmmmmm

and now I've done a few

and it was easy and predictable

and interchanging brass between 338L chambers is awesome

and interchanging brass between 338L chambers VS 6PPC chambers is like the difference between 3shot groups and 5shot aggs......3shot groups are easy.

al

 

[jackie schmidt]

Mesh, I discount the practice of running a Gun Drill into an existing hole, since this is not a very common practice. Gun Drills are designed to core out a solid piece.

I stand by the statement that the truness, as in straight with it's own self, of a barrels ID is predicated on what the Gun Drill does. The reamer will follow that hole, the button, or rifling hook tool, will follow that hole, and the lap will follow that hole. The only way to correct this is with some sort of proccess that will mimic the single point tool boreing or turning proccess.

It is what it is. Actually, it is all academic. Barrel manufacturers are at the mercy of what will allow them to produce a top quality product at a cost that will allow them to make a profit. No doubt, there is, (might be), some high tech proccess that would allow the establishing of a perfect, truly straight hole in a piece of suitable steel. If shooters were willing to pay $5000 for a barrel blank, I am sure all of the current manufacturers would be standing in line to aquire it.......jackie

 

[4Mesh]

Jackie,
I'll just stop here cause I think you're misunderstanding some of what I said and then (rightfully) taking issue with that which was misunderstood. In my case, I think I'm reading too literally what you've written, and should go more with the spirit of what you're saying. We really do disagree less than what it appears.

Al,
Ok, first, I'm thinking that some of your early problems (~10 yrs back) were caused by getting a bad start to the process. As you know, I agree with 95% of what you advocate as well. There are however some things that you mention as problems that I would not have had an issue with, just because I'd have followed a different process sheet.

Actually, in nearly all cases (things you mentioned in the last post as problems encountered by whomever over the years), any one of them was a non-issue to any person who used a process that eliminated it. I mean, how many of the things you heard of were due to an improperly maintained machine? One that wasn't trammed in, didn't have the chuck jaws bored or ground with pre-load, tailstock that wasn't on center, machine that was too light for the job, or whatever? Any number of problems could be attributed to a machine that wasn't really capable of holding the part properly. In my case, all those issues are dealt with before the barrel ever gets ordered, much less chucked up.

To use one of my examples with one of yours, lets take the folks that indicated, pre-bored, but then had a hole that was off center down at the to-be-throat. Now, yes, it's possible that's a crooked bore causing that (damn doubtful I say), but more likely it's a chuck thats ill-maintained. It doesn't take much jaw misalignment to really cause big problems. Now, take those jaws and bore em and pretty much, all those issues go away. The list goes on and on.

Have you ever bored the jaws on your own lathe? Do you own a set of soft jaws? Fyi, I also bore the hard jaws (use ceramic or cbn). Open em wide, preload em, and go to town. Let's face it, if they are not true now, what's there to loose, eh?

To conclude... Now, maybe there's barrels out there with .050 of curve in em. All I can say is that's about .048 more than I've ever seen, and about .0499 more than I'd expect to see as a norm. About the most likely causes for this stuff that's been mentioned was when Mike said about the stock that is not straight, and then centrifugal force bending it when it is up at speed in the drill. Or the chips loading up for whatever reason. The latter more likely causing bigger problems, but also being more likely caught by an operator or by a drill failure.

PS... I've drilled 9" deep holes in 17-4SS at 20:1 L : D ratio using a hand sharpened twist bit in a lathe, and they've never lead off 1/40th as much as is being claimed happens here with counter-rotating gun drills. Honestly guys, if this stuff was happening in the drilling process, the drills would be breaking off. That's a lot of fatigue at 3krpm.

 

[jackie schmidt]

I agree, Mesh.......jackie

 

[alinwa]

OR, barrels are crookedy by maybe even a couple thou in the first 3-5"..........



I'll say the same thing I said on the phone, pony up the 50bucks and try it!! Or friggin' stick a hunk of coathanger in there and touch it with a stylus.... You'll find that even for chambering between centers it'll be a handy tool, nice to KNOW where the throat is before you get there.

LOL

al

 

[4Mesh]

Al,

If I thought I'd be able to use the tools, I'd probably just go get em. I do have a tool grinding shop, so, making them wouldn't be an issue either. As I said on the phone, I don't chamber in an engine lathe. My process is so different, I'm not even sure it would be possible to apply this. Using this method with a hydraulic chuck, bored jaws and hydraulic tailstock for which I obviously have no chuck, is gonna be a challenge. I will play with it in the engine lathe with an already finished barrel that shot. At least I'll have first hand experience, but, without a barrel that is crooked, I just don't know what I'm going to be looking for. Furthermore, without trusting it, well, you know how that affects findings in a 'test'. My brother does have a few other barrels laying around, but, gawd only knows what he'd done to em. His chambers are probably .100 off center on purpose for all I know!

As I said, I've never had troubles finding a center before anyhow, even in 300wby stuff and longer. (404Jefferies, 416Rigby). WSM's are easy.

I'll let ya know if I get time to try this but I'm not thinking my opinion is gonna change.

 

[Clark]

I am on the same page as Chad here.
I have been putting the breech of the barrel in the 4 chuck in a gimbal so that the spider can steer the barrel, not flex it.
I have spent a bunch of time dialing both ends of the barrel so that over some length on a spud on the breech so that the bore is concentric to the lathe spindle in the chamber region, despite the crookedness of the barrel.
I try to get within .0001".

This is good bench rest technique, but if the chamber is off center .005", the rifle is still a one hole gun.

That is because the chamber error has consistent rotational orientation, while ammo eccentricity is applied with random rotation.

.005" of ammo eccentricity can make a 2moa error.
.005" of chamber eccentricity will not even make a 0.2 moa error.

What are you going to do?
Bench rest gets dialed in with compensation for the barrel having a spine.
Deer rifles and varmint rifles will not know if the barrel was even dialed in. Put it in the 3 jaw.

 

[Al Nyhus]

There was a maker that made some of the best shooting 30 caliber barrels you could buy, but they were also the nastiest for a straight hole. You could get sea-sick if you stared long enough down the hole.

Wayne, ain't that the truth!!!!!

The worst one I had 'ran out' .030 at the muzzle but dead nuts on 2" ahead of where the throat was going to end up. Stan Ware timed the big lump at the muzzle at 6:00...'cuz I couldn't think of what else to do with it. It remains, to this day, the absolute best .30 cal. barrel I've owned. The others from that maker...which weren't quite as 'bad'...fill the next places on the list of really good .30 cal. barrels I've had.

My view from the cheap seats...... -Al