looking thru the bore after its dialed in for chambering

Mike, thanks for the response. That's good stuff. Your reasoning with the cutterhead seems inline with what I'd estimate as the outside limits of this stuff.

Jackie,
If I may ask, what diameter of barrel were you looking at? Was that a ppc blank? I ask because as you see above, I"ve done the same thing, and mine I find to be true within essentially nothing. I discussed this at some length with alinwa, and basically, came to the conclusion that we deal with different barrel sizes and that his findings are more geared toward smaller taper barrels. I'm talking about say palma-like shapes. I think you and I are on the same page about barrel setup verification. Though, I tend to think sometimes that it really doesn't make as much difference as we all give it credit for. The number of people who subscribe to the "new" measuring methods tends to make me believe there's not much accuracy to be found in that part of the operation. Certainly, there's not enough to scare me from the firing line when someone sits down beside me and they've chambered their barrel with it running crooked in the lathe! :D
 
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The one anecdotal fillip I'll add to the above..... I generally chamber in the shank portion of the barrel (1.200-1.250-1.350) and have measured considerable runout in this area.

It's certainly a lot easier to chamber "between centers."

(By "between centers" I mean with three points in line, muzzle, leade or throat, and base of chamber.)

al
 
Al,

One thing I did not ask you is, have you ever seen this phenomenon at the muzzle end? Have you ever looked at that end before? If let's say you did see this at the muzzle, what would you do? Fact is, I should think that it would mean much more at that end than it ever would at the chamber end. Especially if part of the chamber end is getting removed anyway. For those who don't know my view on it, I am not a big believer in the bent barrel thing. But, if I was, I'd worry more about the bullet at 3Kfps than I would at 0fps. jmo.
 
4mesh, I've done it on two crown jobs and both ran out about a thou which means the chamber was swinging wildly in an arc prolly 8-10thou off center when I got 'er centered up.

incidentally running the indicator in showed no runout. (I normally just use an indicator on this end anyway.... it's right there.)

AND...... remember guys, I've only done 6 chambers Gordy's way with a couple coming up this week.

I'm just sharing what I've found I'm not preaching!

I will say this, using Gordy's method and preboring and chambering by hand has just set my world upside down. I've got 3 338 Lapua barrels here that I can (and have) screwed back and forth betwixt 2 of Stillers actions. That's 3 barrels, two actions and I CAN SWAP FIRED BRASS!!!!

Two yrs ago I'd have said IMPOSSIBLE! Whoever claims that is blowing smoke or smoking blow or just a snowblowing bloke




or something




I wouldn't have believed it



al

al
 
besides, I just read an article as how the crown don't matter nohow.... I might just start chucking 'em in the threejaw



al
 
Mike, regular LV taper, 1.200 shank.

I might add, most blanks are reasonably straight. As I have said many times, one of the worst places I hate to see one of these "squirrely spots" is right where I am going to indicate the throat. Since, for making weight purposes, I have to cut a lot of the "straight" off, I feel lucky when it still runs real true in that area........jackie
 
Jackie:

That's an interesting post-mortem. I'm happy to say I've never seen a barrel with as many 'features' in its interior geometry. My opinion is that, in the case of the barrel you dissected, the drill wasn't performing properly, because it wasn't correctly shaped, needed sharpening, didn't have enough lubricant/coolant to allow it to work as it should and/or allowed chips to pack up, rather than flushing them, or that the piece of steel was exceptionally inhomogenous (there are such things as poor steel, or steel with inclusions or spots of varying hardness), or a combination of those things. In any case, if the maker had been paying attention to his QC, you'd never have seen that barrel.
You're quite right that, after looking at enough barrels with knowledge of what you are really seeing, anything like .012" runout should be glaringly obvious - and it's actually easier to see where the 'wiggles' are in a reamed bore before rifling: that's where the defects should have been caught.
But, as in every human endeavor, poop happens - I'm sure the maker would have replaced the barrel had you just returned it to him, but we wouldn't have learned what you shared with us, and he might not have been motivated enough to find out as much about it as he did with your help.
P.S. for Al: Keep your muzzle crowns square! Neatness counts!
mhb - Mike
 
Mike,

Back before I became more or less brand loyal, I'd tried most of the big name barrels. The only barrel I ever saw that exhibited the sort of 'bore wander' that folks here claim to see, was a hammer forged barrel. And even that one only had any significant issue at the one end for a very short distance. It shot terrific btw.

Most of the stuff I deal with any more is an unturned blank, usually 1.500 stock. Maybe the folks at Shilen have a real nice chuck on their gun drill, maybe they take more care putting stock in it, whatever. They sure are drilled straight... And for me at least, they stay that way after tapering or od turning.

Maybe the final grinding on the OD's you speak of can cause some issues. But then too, I've purchased (long ago) barrels made that way and tapered by the barrel manufacturer, and those were very straight when rolled on a surface plate too. Yes, all mine get that sort of treatment.

@Al,

Al, having the muzzle running eccentric by 8-10 isn't enough to even spark my interest. I'm not sure I'd bother with that myself. I'm talking about the folks who are seeing that much in the first 2". I could easily see 8-10 with the naked eye as long as the hole was centered in the part. If you think about it, that's not very much angle when spread over ~28-30". Probably not near the angle an ejector pin causes with the chambered round.

As for Jackies nightmare barrel, I'd agree with Mike, chips loaded up in the drill, insufficient coolant pressure, whatever. That was a Friday@5 barrel. I wouldn't expect to see too many more of them.
 
You've heard of people getting 8-10 thou BORE RUNOUT in just a few inches?? What I'm saying is that after straightening the bore at the muzzle for about 6" I might have had 8-10 wobble each way on the outboard side.

Something wrong there! I think the most I saw is around .002 in 6 inches of bore. But that's guessing, I just center up to eliminate the wobble I don't figger any offsets.
 
This bore straightness issue has been discussed quite a few times in that past. While it gives one a warm-n-fuzzy feeling when you see a bore spinning that appears quite straight, it's not the determining factor of a great shooting barrel.

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.

I have to say, the barrels I've seen in the past several years seem to be much better for bore straightness than before. Some will show a bit of "wobble", but most are quite straight.
 
4Mesh said:
Maybe the folks at Shilen have a real nice chuck on their gun drill, maybe they take more care putting stock in it, whatever. They sure are drilled straight...
Click to expand...
Except for the new .22RF barrel we just fitted. It ran out even to these tired old eyes, both inside and out . . . a lot. Probably will shoot like a house afire.
 
My findings mirror Wayne's.

Al,

When people here use the Gordy method and say they have a muzzle running out 5-10, I don't even think about those. To me it's meaningless. I won't get into reasoning that with folks, it's just a difference of opinion.

However, either I am really bad at reading what people write, ORrrrrr, they as a rule are not so good at writing what they mean. Because what I read people saying is that they find .010 of runout or wander in the first 6" of barrel, to which I say... Well, anyway... I'm now taking it from you that these people saying they measure runout in the breech really mean they get the first 6" of barrel running "true" and then measure the other end and say that number as if it were at the breech? Yes? Just not being clear?

Part of why I am confused here is that other folks refer to sporter barrels saying they are worse (which they are) and I've seen sporter barrels that were off .200 after being dropped or whatever. Sooo, I'm thinking, ok... whatever, go measure your sporter and have fun, this has nothing to do with BR blanks.

Either way, if folks are "fixing" this for .002 over 6", more power to em. We're still talking about a bullet that has room around it that would allow it to cock in the throat by angles 100 fold larger than this. Ok... I'll again leave these discussions alone. :confused::confused:

btw, now we're back to my original contention that adding a device to the indicator is bogus... That would never hold water in an inspection environment when looking for tenths.
 
But Charles, again, we're talking about a really small diameter barrel, no? Then, "A Lot" can mean different things to different folks. To me, .002 would be a lot... maybe even .001

You two posted while I was typing earlier.
 
Drilling

Drills and reamers that have pilots, (a gun drill is actually back piloted), will tend to follow what ever hole is already in something.

That is why every thing that happens to a barrel is predicated on that initial hole that the deep hole proccess establishes.

Go to the major manufacturers of deep hole drills such as are used in barrel making, and what they can guarantee for straightness, as in so many tousanths runnout per foot, is pretty in line with what our major custom barrel manufacturers are producing......jackie
 
jackie schmidt said:
Drills and reamers that have pilots, (a gun drill is actually back piloted), will tend to follow what ever hole is already in something.
Click to expand...
Jackie, that first line was a bit confusing. I assume you are including the gun drill reference just as additional info, like btw, gun drills have a bearing surface..., not to imply that the gun drill is "following" anything. There's no starter hole, no pre-drill for gun drilling, etc. The reamer, yep, it follows the hole more than less.
 
Another thing. Many get the term "runnout", "bent", and "crooked" mixed up. In machinist terms, something is bent that was originolly machined on the same plain, and for some reason the piece got distorted causing one section to now "runnout" with another section. Technically, you can straighten this to where it will all run on the same plain again. We do this all the time with large shafts.

If something is machined crooked, that means that the piece has areas that do not run true with each other after final machining. For instance, if you had a shaft, and you needed to machine a new fit on the end, and you chucked it up to where the surfaces that were not going to be machined ran out, and then machine the new fit, it would be machined "crooked" with the rest of the shaft. You CANNOT correct this by straightenning.

This is what happenns in a barrel. The Gun Drill might start dead true and following a truly straight plain with the machines center line, but then wonder off at different times. these places are, for all practical purposes, machined on a different plain. Yes, you can kink around on the barrel with a straightenning machine, and do what we call "split the difference", but they will never be truly straight with each other, unless they were initially established truly straight in the beginning.

I have shooters say, "there is no way a Gun Drill can drift that far in so short a distance. Well, I could care less what it is not supposed to do, all I look at is the results. And when you have two surfaces in a barrels ID that run out .010+ with each other in a 7 inch length, something is going on that defys the norm.

The reason many barrels get out that are crooked as all heck is because the barrel manufacturer has to reason to ever look at the bore the way we do, as it is spinning in a lathe. Think about it. They drill it, ream it, rifle it, and lap it, and at some time turn the profile. At no time is the barrel ever set up in a lathe so that someone can actually look at what is going on.

In short, the manufacturers keep their tooling up to date, and rely on the machines to do what they are supposed to do. That is the nature of the business. And considering how well these things shoot, it is a pretty darned good system.

If I am wrong on this, please correct me........jackie
 
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4Mesh said:
My findings mirror Wayne's.

Al,

When people here use the Gordy method and say they have a muzzle running out 5-10, I don't even think about those. To me it's meaningless. I won't get into reasoning that with folks, it's just a difference of opinion.

However, either I am really bad at reading what people write, ORrrrrr, they as a rule are not so good at writing what they mean. Because what I read people saying is that they find .010 of runout or wander in the first 6" of barrel, to which I say... Well, anyway... I'm now taking it from you that these people saying they measure runout in the breech really mean they get the first 6" of barrel running "true" and then measure the other end and say that number as if it were at the breech? Yes? Just not being clear?

Part of why I am confused here is that other folks refer to sporter barrels saying they are worse (which they are) and I've seen sporter barrels that were off .200 after being dropped or whatever. Sooo, I'm thinking, ok... whatever, go measure your sporter and have fun, this has nothing to do with BR blanks.

Either way, if folks are "fixing" this for .002 over 6", more power to em. We're still talking about a bullet that has room around it that would allow it to cock in the throat by angles 100 fold larger than this. Ok... I'll again leave these discussions alone. :confused::confused:

btw, now we're back to my original contention that adding a device to the indicator is bogus... That would never hold water in an inspection environment when looking for tenths.
Click to expand...

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.

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.

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.

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. If you do you'll find measureable runout in the two-two and a half inches you can measure. 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? For myself, I'm not "looking for tenths" I'm just setting the throat to be as wobble-free as possible.... while checking an inch or so further in and back out to the rear. Because I can! :)

And straightening this section, aligning it to cl of the machine.

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

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
 
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