muzzle runout Gordy's method

Dennis, I guess that would be one way to put it. No matter which way you dial the bore in, the bullet's going to follow the bore where it goes. The majority of time, the 'old' method works great, especially with the straighter barrels, but at times the slight (and almost always measurable) chamber to bore misalignment caused issues I didn't like. Since I started doing it the 'new' way, I have never had any of those issues again.

And you are correct, it's bullet to bore alignment I'm most concerned with. When using the 'old' method, almost always the chamber and the throat itself would measure perfect with zero runout (you're machining all that in so it better be straight), but then I could often measure even just 1/4" ahead of the throat and get measurable runout, and that does concern me. Think about it -the neck length and bearing surface of the bullets are usually longer than 1/4", so this leads me to believe the bullet is still partially in the neck of the case as it's starting into the bore ahead of the throat. Since the bore the bullet is starting into isn't lined up on quite the same plane as the bullet/cartridge case, the bullet is going to be slightly distorted as it's being driven into the bore at this slightly different angle. I never argue with anyone about how much difference this actually makes, but for myself when I can so easily correct this slight misaligment by how I dial my barrels in, I will.

I should comment on one other thing that there seems to be a lot of confusion about with my method of dialing-in barrels. Off-setting the muzzle ever so slightly to get the bore dialed in like I prefer has never presented any problems at all for me. I was sure nervous about it at first but after seeing the benefits and never seeing even a hint of a problem in over 1000 barrel setups like this, I sure don't worry about it any more! Since the muzzle end of the barrel is only sitting anywhere from .005" to .020" higher in the barrel channel doing it this way (actually about 1/2 that since the forend usually only extends about 1/2 way down the barrel), you sure can't tell it by looking like some people are afraid of. The main thing I noticed (and one of the reasons for doing it this way) was if I indexed the high side "up", I could get a few more MOA of useable scope elevation adjustment for the 1000 yard shooters.

Al, I always hate learning things the hard way like that. But look at the bright side - you gained more experience when that happened, and I'll bet it never happens again!!!! :)

Gordy Gritters
www.ExtremeAccuracyInstitute.com
 
Charles, I missed your post while I was working on my last response. Yes that's right. If I dial it in the old way at the throat and the muzzle, then because of the curve in the bore, it will not be on the same plane where it intersects the chamber. This is why when you chamber barrels using the 'old' method, it is so critical to get the bore dialed in true exactly at the throat to get the bullet centered there.

When I dial a barrel in by my method, I dial the throat and 2" ahead of the throat to run straight and true -then you can put the throat anywhere you want in this area and it will be perfectly aligned to the bore. Then I drill and bore the chamber hole true to the bore, so now the complete chamber and at least 2" ahead of the throat are in alignment. But to do this the muzzle will end up being offset slightly, which I've never been able to find any downside to at all.

Sailhertoo, I am in the process of finishing up the bore-lapping video, so hopefully it will be ready this spring or summer sometime. I've quit taking in new work for now since I will be moving to the KC area this summer and need to get my backlog worked down a ways. Then I plan on doing less gunsmithing and more with the classes and instructional DVD side of my business. I've been accuracy gunsmithing for over 24 years now and it's time to pass along the things I've learned to people who want to learn to do chambering and rifle accurizing themselves.

Gordy Gritters
www.ExtremeAccuracyInstitute.com
 
Gordy, I can't remember if we met at the 2005 Nationals in Pella. It was a bad year for me, so Dave Tooley & Steve Shelp figured I needed some relief, threw me in the back seat of the 250, & hauled me to the match. Tooley, Shelp, Regan Green & I were "The Good, The Bad, and The Grumpy" team. I have some good memories from the match, but wasn't in the best of health. If I've forgotten meeting you, I apologize.

If we didn't meet, I sure "met" some of your rifles.

OK. With, say, a 300 Ackley, you're talking about 3 inches down the bore to the throat, and about 5 inches down the bore to get 2" ahead of that. We've used a 4-inch stylus on an Interapid, but I've never quite trusted it.

Now if you've covered this in your video, you may not want to say here, but just what indicator setup do you use, if the measurements are taken before drilling & boring? Or are you using the "grizzly" rod & measuring at the breech?

TIA,

Charles
 
Chamber to bore runout does not exist with "floating" holders or pushers like the Bald Eagle. The bushing follows the bore if it wanders and a concentric throat results. There are many ways that have worked and as a machinist and engineer looking at some techniques and look in awe at results that are achieved. Some items are crucial for any method to work reliably--the spindle bore must be parallel to the axis of the ways and the tailstock travel needs to be parallel to the axis of the ways. If those two items do not exist and you use a method such as the one Gordy suggests-the result may feel good, but will not be aligned to the centerline of that bore.

And as I stated in the previous thread -if you indicate the throat area to .0002 and then cnc or taper bore the chamber to .000005--you certainly have a straight chamber to axis of lathe and perpendicular to the barrel shoulder-but the throat to chamber will be .0002 TIR as was indicated in.

Just a little more food for thought and discussion

jim
 
Charles, we did meet at the 2005 Nationals, but when there are so many folks to meet at one of these events, there's no way to remember everyone. I also remember your team-members (great shooters and great guys), and remember laughing about the team name you guys came up with. Good times!!!

Yes, on your 300 Ackley scenario, I do the dialing-in by measuring at the 3" and 5" marks to get the bore dialed in. I never dial it at the breech any more since that part of the bore is going to be drilled out and trued with a boring bar after the barrel is dialed in, so you're going to be machining it true to the section of bore you've dialed true ahead of the chamber.

I continually experiment and try to find better ways of doing things. If I remember right, at the time I made the Grizzly video I first dialed the bore in, fit the action, then pre-drilled the chamber. After pre-drilling the chamber, I double-checked the bore dial-in with my long-reach indicator and made any slight adjustments to make sure it was as true as I could get it.

But since making that video, one of the changes I now do is to predrill the chamber hole first of all, before dialing the bore true. Saves a little time by usually only having to dial it once, not twice like sometimes happened before, since now I can reach the bore ahead of the throat with my indicator after initially dialing it with the range rod.

So my current process goes like this: I get the barrel into the lathe, dial the bore at the chamber end to running pretty straight - within .001" or so - just get it close. Then I measure and pre-drill the chamber. It's not true yet, so now I can reach in with my indicator and either dial it in just with the indicator (forgo the range rod entirely), or use the range rod to get the bore running as straight and true as that will allow, then fine-tune any remaining runout to zero with the indicator moving from the throat to as far forward as it will reach (usually 1 1/2" with the indicator tip I use the most). This works well for most cartridges, but I use the range rod for sure on 223 size chambers (indicator is larger OD than the pre-drilled hole) or on extremely long chambers (indicator isn't long enough to reach far enough up the bore to dial it properly). The range rod is accurate enough to work just fine in those situations if you use it right.

After getting the 1 1/2" or 2" section ahead of the throat dialed-in, I true up the pre-drilled chamber hole with a boring bar to match, so now the entire chamber area and up to 2" ahead of that is all running true and on the same plane. Now I fit the action and then use the chamber reamer to finish the chamber, indicating several times during that process to make sure there is no chatter developing and that the bore stays dialed-in. If something changes (rare, but it happens) then I can easily correct it right when it starts - before things get out of hand and it's too late.

I'll just mention here a couple things that I've seen other posts back and forth about. One thing concerns whether to bore the chamber hole straight, or to match the taper of the cartridge. I think either method will work fine, but for me it's quicker and much easier on the variety of chamberings I do to always drill straight and let the reamer establish the taper. The other thing guys wonder about is whether you should have the bushing be in the throat or not when you start the reamer into the pre-drilled chamber. In my experience, it makes no difference at all in most cases. Many of the chambers I do are longer ones so the reamer often cuts 1/2" to 1" before the bushing finally starts to enter the bore. I can't tell any difference at all, and believe me I measure and indicate numerous times throughout the chambering process, so if something was happening I would catch it. Once in awhile the reamer will want to start chattering when it first enters the bore, but it doesn't seem to matter if the bushing in the bore or not. When that happens, just bore that true and start the reamer carefully again (I usually start the reamer while slowly rotating the chuck by hand since this seems to minimize the tendency to start a chatter when the reamer first enters the chamber).

Let me give you the part numbers of the indicator setup I use - I get this all at MSC Industrial Supply:
06249411 Mitotoyu dial test indicator kit
06445464 1 1/2" long indicator tip (.080" diameter which seems to work the best for dialing in bores)
99046633 2 3/4" long indicator tip
09560376 NOGA magnetic base/indicator holder

Jim, I'll have to disagree with you on some of that. You have to take tool flex into account, so when the bushing tries to follow an untrue hole ahead of the chamber, the reamer tip (extremely small diameter at the bushing) will flex and the body of the reamer will still not cut perfectly true to a crooked hole ahead of it. It's a matter of degree, but I've measured this many times using both floating and fixed reamer holders, and can almost always measure some runout when things aren't lined up properly, which I don't like to see. You are definitely right about having the lathe headstock and tailstock aligned to the ways, and needing to use a floating holder or pusher then.

I'm leaving now for a couple days, so I'll let guys talk this back and forth now. Everybody learns from these discussions and that's great!!

Gordy Gritters
www.ExtremeAccuracyInstitute.com
 
A little off topic but, I hope the move goes smooth and welcome to Missouri. But if you're tired of snow move on down to the Springfield area, we get a lot less snow then KC.
 
It seems to me if the reamer aligns itself with a crooked bore, the chamber at the base will be oversize or oval????

Jim
 
IndianaJames said:
It seems to me if the reamer aligns itself with a crooked bore, the chamber at the base will be oversize or oval????

Jim
Click to expand...

Yes.

The way I learned to chamber 30+yrs ago was to set up between centers, run a piloted roughing reamer in to hog out a hole and the "finish" it with a finishing reamer. The "control" was to go through elaborate contortions to "align" the tailstock.

nasty.... and completely NON-repeatable.

For 25yrs I convinced myself that the only way to get good chambers was to live with your machine day in and day out so that you knew intimately it's every little hump and wiggle. The "zen of knowing your equipment" was well beyond my ken so I farmed all my work out to some of the best gunsmiths on the planet.

And then Jerry Sharrett posted a pic of a reamer driver.

And then Gordy came along.

And I've turned out the best chambers I've ever SEEN in the last couple mo. On a dead cold piece of iron. I think nothing of chambering up a fireform barrel "a half thou long" just to get the feel I want. And knowing that when I'm done the brass will be perfect fit. I've even done FF chambers between centers by using Gordies rod to reach in and find the throat and then drilling/boring out the intervening metal and aligning with the throat, not even caring if the bore's straight or not.

al
 
IndianaJames said:
It seems to me if the reamer aligns itself with a crooked bore, the chamber at the base will be oversize or oval????

Jim
Click to expand...

Not if you are using a ball against flat pusher.

Yes-if you have "chucked" the reamer hard or are controlling the tail of the reamer with a point in a center drilled hole in the back of the reamer.

Jim
 
Jim...

Are you saying the reamer will flex enough to not enlarge the chamber as the pilot follows the crooked bore?

Thanks,
Jim
 
If I understand Jim Borden (and there is a good chance I don't, or haven't thought it through well enough), the best chambering would result not from pre- drilling & boring, but by using (pushed) piloted roughing, then finish reamers.

And if that is correct -- essentially relying on the reamer following the hole in the bore -- indicating in the barrel to the 1/10,000 region -- shouldn't be terribly important.
 
Charles E said:
If I understand Jim Borden (and there is a good chance I don't, or haven't thought it through well enough), the best chambering would result not from pre- drilling & boring, but by using (pushed) piloted roughing, then finish reamers.

And if that is correct -- essentially relying on the reamer following the hole in the bore -- indicating in the barrel to the 1/10,000 region -- shouldn't be terribly important.
Click to expand...

Except that if the bore IS crooked then the result will be a chamber that's cocked to the boltface.

al
 
alinwa said:
Except that if the bore IS crooked then the result will be a chamber that's cocked to the boltface.

al
Click to expand...

And oversize if the bore curves since the reamer will work to cut across the chord of the curve.

Fitch
 
I think people are giving up on thinking mechanically here.

Listen, lets say we have a 30 cal barrel and it is not straight by some epic amount. Ok we go to put the reamer in, the reamer cuts a new hole. Now, that amount that the bore is imperfect is not significant once you open the hole another 200 thou, using a reamer that cuts on both the leading edges and the sides. The hole will be oversized by whatever amount you hold the tool eccentric to the workpiece. meaning it will tend to act as a boring tool if the butt of it has been held too tightly as suggested above. As to it cutting a banana cause it "follows", listen, it can't. It might put parts of the hole where they should not be, they might be the wrong size, they might be a lot of things, but bent ain't one of em.

People have some gigantic errors envisioned in their minds here and are thinking about things like that. Even the people who advocate this method of setup, admit that the errors are within what a floating reamer holder/pusher will accommodate. If you are out by more than that, shame on you, you can see that with the naked eye.
 
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we really are idiots aint we fitch???

basically what we're being told is "it don't matter where that pilot takes the nose!!! the setup will FIX IT!"


Jerry, I thought we weren't speaking? But since we are :)

IF the throat area is further in than you can reach, IF you can't measure that it's dialed to the centerline, then it may not be..... And IF it's not in the center of rotation then the pilot will drag the reamer over.

or IF you were to do the old rougher/finisher treatment using a fully floating or pushed piloted reamer and IF the section of bore you're working with isn't aligned with the cl of the spindle, then you will get a chamber that's cocked to the center of rotation. The chamber will line up with the bore but will be cocked to the boltface, the threads, the action face etc...



Phil, who said banana??? You can't cut a banana unless you got one a' them new HDD rigs :p

lol

al
 
I feel like we're really getting off course here.....

I think everybody agrees that YOU MUST SET THE THROAT TO THE CL OF THE LATHE SPINDLE.

The question is, CAN YOU with your equipment?

Then the second question becomes simply what path you follow to get to that point. Do you follow the bore-section to hit the throat or do you work from the other end and align the muzzle with the throat. In either case proper technique will yield good chambers.

All this other stuff about buggering up the chambers is another subject entirely.
 
You know if you indicate to just in front of the throat and taper bore to that indication, you don't need no damn bushing.
Butch
 
Butch Lambert said:
You know if you indicate to just in front of the throat and taper bore to that indication, you don't need no damn bushing.
Butch
Click to expand...

I' agree with that. The reamer will self center in the taper bored hole, which is by definition concentric with the spindle axis, and make a chamber centered on the lathe axis pointed at the point in the throat that was indicated before it was bored.

Fitch
 
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