Fixing chamber runout

Boyd Allen said:
Al,
Why would anyone use the parts of the barrel that are belled from lapping to indicate from? Before (and even after) the Grizzly (or Gordy) rod came along, some used Interapid type indicators with very long contact points, or range rods of various types. I have even read of the use of precision ground pins. After chambering, the barrel is reversed in the headstock and dialed in the same way before cutting the crown, so that it is square to that end of the bore.

Here is a good thread on dialing in a barrel. Gordy Gritters wrote some good information about his method in post #19.
http://forum.accurateshooter.com/threads/indicating-in-barrel.3746886/
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If you feed a reamer into the end of a bore inches away from the indicated portion, using it "as a drill," it will generally be wallowing, lapping bell or not. This is (has always been) hard on the pilots and on the reamers. Which is why the commonly accepted method has devolved to hacking off the lapping bell, centering up the bore between centers "to get the reamer started good" and driving on....preferably with lots of fluid.

I repeat, if anyone has another method for indicating bores which is even remotely as good as Gordy's, I'd like to hear of it.

I've Deltronic pins, hollow ground pins, ground rods with and without ground bushes, the longest test indicators made...... all useful tools in their places but they serve no function for dialing in barrels


IMO


Regarding ground pins......I've pins in lengths from 1/2" to 3" and I'll NEVER AGAIN try sliding a tight-fitting pin longer than the typical reamer bushing into a barrel.

You wanna' find out barrels is crooked???

hooahhhhhh, nasty like two dawgs stuck together and me without a water hose...
 
breaking news..washington state discovers...rifle bores just ain't straight!

alinwa said:
Regarding ground pins......I've pins in lengths from 1/2" to 3" and I'll NEVER AGAIN try sliding a tight-fitting pin longer than the typical reamer bushing into a barrel.

You wanna' find out barrels is crooked???

hooahhhhhh, nasty like two dawgs stuck together and me without a water hose...
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JerrySharrett said:
Are you making the assumption that the bullet will straighten the crooked bore by your car in the tunnel analogy? The bullet will take the exit path of the last 3/4" or so of where that part of the bore is pointed. If that last fraction of bore is not pointed in the direction of the recoiling rifle, then what?
.
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I think that even if we have both ends of the barrel indicated perfectly before we chamber, if the barrel has any curve, the last fraction of the bore still will not be pointed in the direction of the recoiling rifle. We could indicate the muzzle end of the bore so it is aligned perfectly with the recoil path of the rifle, but that creates a lot of problems at the chamber end. So in my mind, it makes more sense to make sure the bullet is spinning as perfectly around it's axis as possible, and in my mind the best way to do that is indicate the throat area to be as perfectly in line with the chamber as possible.

All that being said, I have chambered my rifles using both methods and have not noticed a difference. And certainly, there have been rifles chambered using both methods that have done plenty of winning. This makes me think that some things, within reason, may not be as important as we think.
 
James Lederer said:
I think that even if we have both ends of the barrel indicated perfectly before we chamber, if the barrel has any curve, the last fraction of the bore still will not be pointed in the direction of the recoiling rifle. We could indicate the muzzle end of the bore so it is aligned perfectly with the recoil path of the rifle, but that creates a lot of problems at the chamber end. So in my mind, it makes more sense to make sure the bullet is spinning as perfectly around it's axis as possible, and in my mind the best way to do that is indicate the throat area to be as perfectly in line with the chamber as possible.

All that being said, I have chambered my rifles using both methods and have not noticed a difference. And certainly, there have been rifles chambered using both methods that have done plenty of winning. This makes me think that some things, within reason, may not be as important as we think.
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+1

When and if anyone is ever able to quantify WHY some barrels shoot great and others don't, we'll be getting somewhere.

Pete
 
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Don't much worry about the exit point, shoot it to zero bullseye. For what it is worth, I just finished up a Mauser barrel, 330-06, and checked the runout with an Interrapid indicator, .005" max TIR, so what? Now what?
 
And no matter what you do vibration and the pressure driving the bullet is making the barrel move around as the bullet travels the length of the bore.

There are any number of simulations showing the motion.
With enough measuring gear you can determine how much a barrel droops from gravity since it is supported at one end and not the other.
It is a steel cylinder hanging off an action in space.
 
I'd get a new gunsmith, or send the current one to class.

Jim Kobe said:
Don't much worry about the exit point, shoot it to zero bullseye. For what it is worth, I just finished up a Mauser barrel, 330-06, and checked the runout with an Interrapid indicator, .005" max TIR, so what? Now what?
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please explain to me why .005 runout is acceptable gunsmithing on a bbl.
just makes no sense to me, regardless of the action it goes on.

Zebra13 said:
I believe Mr. Kobe is a member of the American Custom Gunmakers Guild, which is a rather exclusive club.

Justin
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CMaier said:
please explain to me why .005 runout is acceptable gunsmithing on a bbl.
just makes no sense to me, regardless of the action it goes on.
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CMaier,

I find .005 excessive, also. But for his application, it probably doesn't matter a whole lot.

I don't think he needs a new gunsmith.

I think you need help on your delivery.

Justin
 
Getting back away from the I pi$$ on you then you pi$$ on me to the original subject of this thread which is "chamber runout".

Runout at the point where the bullet enters the barrel bore from where the bullet starts is the most important alignment area. If the bullet has any offset in its merger that bullet will start down the barrel with some in-bore yaw....bad.

If the chamber runs out at the cartridge base to where the firing pin does not hit the primer close enough to center to provide consistent ignition there will be a variation in velocity from shot to shot..bad.

If the barrel bore at the muzzle is not in reasonable alignment with the action/stock assembly to where the recoil is skewed from the centerline of bullet path...not good.

If you are rebarreling your grand dads old thurty-thurty used to shoot deer at 25 yards then perfect alignment is not too critical. But, if you are trying to get your bullets to go through the same hole at 300, then dial in your chambering setup very closely.



.
 
I just got pissed when I read some of the comments and thought "what a bunch of dickheads" I went back and read my thread and lo and behold it came to light; I forgot one zero. The actual runout was .0005", so sorry for setting all this up, it was not intentional.
 
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