Chamber run out issue

Is Run-Out...Run-Out??

We strive to keep chambers within "tenths", but I have checked fellow shooters loaded rounds that show as much as .003.

Does it make sense to put a crooked round in a perfect chamber. As far as the bullet is concerned, does it matter if it enters the lands crooked because of loaded round runout, because the chamber is a tad crooked with yhe lands and grooves??.........jackie
 
As long as you shoot in the wind, how is anyone going to know for sure?
 
Jackie,
Try this. With a loaded round total neck clearance of around .0015, and an the bullet seated well into the lands, chamber a round that you have kinked to over .004 out, pull it back out and remeasure runout.
 
jackie schmidt said:
We strive to keep chambers within "tenths", but I have checked fellow shooters loaded rounds that show as much as .003.

Does it make sense to put a crooked round in a perfect chamber. As far as the bullet is concerned, does it matter if it enters the lands crooked because of loaded round runout, because the chamber is a tad crooked with yhe lands and grooves??.........jackie
Click to expand...

Jackie,

If your sizing dies right there's no more than a tenth or two of play in the chamber.

If your neck clearance is normal (.002) then you've got no more than a thou possible clearance in any direction....

And if you're "touching" or "into" or even ".005 off" the lands there can't possibly be play there........

So how could crooked ammo stay crooked if your chamber is straight?

al
 
Alinwa

I have done this and mentioned it here before. When the snow piles up this winter, I'll do it again. Take a loaded round, offset the bullet in the case
so as to be crooked. Indicate it so you know how far off. Shoot this in a pile of snow. For future reference, you can even write on the bottom of the bullet. That 68 grain bullets don't get far in snow was a great surprise to
me, but even more so was the fact that they show no damage. What
will be seen is that a crooked bullet can show lands marks starting closer
to the point on one side than the other. Try it.When the snow melts in the spring, they will be laying on the grass
 
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Butch Lambert said:
I use a very loose bushing inorder that my reamer will follow the prebored hole.
Butch
Click to expand...
Butch, in lets consider an unusually crooked bore, do you really want the reamer to follow the prebored chamber body or do you want the nose of the reamer to merge with the bore however out it is with the chamber base. I think you want the "business end" of the loaded round to smoothly blend into the chamber neck/leade.

In the loaded round there is some flexability and that loaded round will bend to fit as long as the leade diameter is just 0.0002" over bullet diameter and the chamber neck/cartridge neck are a good fit.
 
Jerry-Jerry, If you indicate the grooves at the throat, how crooked can it be to the leade? If one makes a 90deg there, I will send the barrel back. You are taper boring and reaming to that indicated point. How much closer can you get? If you have a snug bushing stuck out on the end of the reamer, it will follow the crooked bore and have a tendency to cut a larger hole at the base of the cartridge.
I'm gone hunting, will be back Sunday.
Butch
 
I have nothing against preboring, if nothing more it saves wear on the reamer.
I also don't know anyone who has a tenth indicator that reaches in to where the throat will be untill the prebore is done. Therefore, you cannot
indicate to where your going initially, only creating a guide. If this guide
is not true with where you are going, what will put it back on course.
Using a proper pilot,the throat will be centered regardless.You also have
the option of rechecking and reindicating every .100 or .200. Any
lateral preload given in the prebored chamber has less influence, and there will be lateral forces if that prebore is not on course with your destination. If the pilot
is true, you can indicate in the front area of the neck which is not as far


in as the throat.Not all indicators are reliable when hopping over lands


which are 90 degrees to the axis of the indicator finger. (basic Machine
shop text) Electronic height gages go nuts when this is done. I would much
prefer the mouth of the chamber to be large by .0003 than the throat
to be off center by that much.
 
AZLarry,

Did you indicate both ends of the barrel?
How well did you indicate bore ( in thousands)?
What is the runout spec on your lathe's headstock?

Just to let you know how I do it,

I only use a 4 jaw chuck (easy to indicate)
I indicate both ends of bore to less than <0.001" (usually <0.0005")
I use caliber specific PTG range and indicator rods
I use an interchangeable pilot reamer mounted in a floating reamer holder

My guns are guaranteed to produce sub 1/2 MOA accuracy for a five shot group using Factory Match Ammunition. Accuracy verified @ 100 yds. and 500 meters. Haven't built one yet using this method that did not meet the guarantee.

Yes you can build to tighter specs, that's up to the individual.

Hope this helped.
 
Is it possible that the barrel is being "warped" between the 4 jaw chuck and the out-board spider???
I use a .050" thick soft copper sleeve made from copper sheet around the barrel in my 4 jaw chuck to ensure that the barrel can align between the 4-jaw and spider as adjustments are being made to center the barrel at both ends...
If you use a rigid material around the barrel in the 4-jaw...the 4-jaw chuck jaws have a larger contact surface that the spider screws, and may be causing a change in alignment once the reamer starts to cut especially in the shoulder and body area...
 
Bob Kingsbury said:
I I also don't know anyone who has a tenth indicator that reaches in to where the throat will be untill the prebore is done. Therefore, you cannot
indicate to where your going initially, only creating a guide.

.
Click to expand...
The Interapid indcator does!!! Even with something like the Mitutoya, just predrilling will let you get to the throat of something like the PPC and BR.
 
To: Shooter53

Did you indicate both ends of the barrel? No, I indicated the barrel from the chamber neck area forward for about 1/2" inch. Looking back maybe I should of indicated farther into the barrel (ie: add up the neck length, free bore length, throat angle and reamer bushing it is about 1" of total length.

How well did you indicate bore ( in thousands)? .0002-3" with 2.750" long stem interapid indicator. Not the best setup up but only one that can go that deep with the small bolt face cartridge.

What is the runout spec on your lathe's headstock? .000050" (Hardinge toolroom lathe)
 
AZLarry

Your lathe headstock runout is more than adequate (great actually) so that is not the problem.

You indicated the breech end of the bore well enough so that is not the problem.

Understand, if the muzzle end of the bore is off center by just 0.007" to 0.008" that can wobble the breech by at least 0.001" on a 26" barrel.

I know you indicated the bore at the breech 2-3 ten thousandths at a distance of 2.75" but you may not have had enough depth in the bore to really align the indicator.

The PTG indicator rods are machined to be used on an already chambered barrel with such a fine taper as to allow the rod to set about 2" into the bore past the freebore.

The range and indicator rods are less than $40 each. Having both and being able to indicate both ends of the barrel is very effective and allows you to see how much movement the breech end travels for a few thousands of movement at the muzzle.

I'm sure there are better ways to accomplish the same thing but I thought I'd just throw out a quick and easy way to get there.

Good Luck
 
don

I understand what an air gauge is for, just was thinking out of the box, IE, some form of non-contact method of centering a bore.

If you predrill a recess in a barrel and then indicate, and correct at the throat, that will not mean the chamber is parallel to the bore.

Another thing to keep in mind is that most indicators are calibrated with a probe of about 1/2" long, when you replace that with a long probe your "tenths" are no longer "tenths".
 
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Jerry Sharrett

I have both of those indicators, and I use them. They almost make it
the needle is set to one side a bit, and that detracts from the 3/8
diameter nose. I can indicate the front of the neck, but when in the throat
you are actually at 7:30, not an ideal 6:00.
 
Shooter53

Shooter53 said:
Understand, if the muzzle end of the bore is off center by just 0.007" to 0.008" that can wobble the breech by at least 0.001" on a 26" barrel.
Click to expand...

Are you talking about a barrel set-up as AZLarry describes, i.e., breech end held and indicated in on a 6 jaw chuck and apparently, as I understand it, the muzzle end not indicated in?

Justin
 
To: TRA

The Interapid indicator described is made to operate with a 2.750" stem with a resolution of .0005" on the dial.

To: Shooter53

I'm following the principles described by Gordy's video on barrel alignment. Bore alignment only at the chamber area, what the muzzle is doing is not critical.

To All:

I have made a few changes to my setup:

1) Made the alum. split ring holding the barrel in the chuck thinner. Last week I was using a 3/8" wide piece, changed to a .060 width so the barrel can "pivot" easier with the muzzle end spider.

2) Modified the floating reamer holder with a spring for stability but still be able to move in all directions for proper alignment. Also changed it so I don't have to hold the handle while the reamer is cutting. If I get the wife's digital camera I'll take a picture of it. Interesting contraption. *If does not work as planned will have to "simplify" and go with the Mr. Bryant type of holder.

3) Will try to indicate the bore from the neck to the end of the reamer. Will leave off the reamer bushing.

4) Will pre-bore the chamber to 1.425 (just short of base to shoulder length of 1.432") depth with a .4 degree taper. Leaving .005" on each side for the reamer. The closer I can get to a finished chamber BEFORE reaming it can't hurt. Hopefully!

Should have this "experiment" started within the next week. Will keep you posted.

Always good to hear from you all. Your input is very helpful.

Thanks, Larry
 
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TRA said:
don

I understand what an air gauge is for, just was thinking out of the box, IE, some form of non-contact method of centering a bore.

".
Click to expand...


Guess I dont have "out of the box vision"..........how do you center a bore in a lathe with an air gauge?..............Don
 
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