Chamber run out issue

AZLarry said:
. Bore alignment only at the chamber area, what the muzzle is doing is not critical.

Larry
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Let me get this straight in my mind, you are concerned with 0.0015" runout in the chamber body of a 223 Remington but where the muzzle is pointed, the exit point of the bullet, does not concern you???
 
AZLarry,

Sorry, I'm not familiar with Gordy's method of barrel alignment.

My reference is from Darrel Holland's 2 video set "Custom Barreling" from AGI (American Gunsmithing Institue), The Gunsmith Machinist by Steve Acker and "The Complete Illustrated Guide to Precison Rifle Barrel Fitting by John L, Hinnant.

Good luck with your project.
 
Link to a excerpt from Gordy's barrel setup video
http://www.youtube.com/watch?v=aII2tbavKnM
It looks like he has possibly used double stick tape to hold shims onto the faces of the chuck jaws, and that they only extend a short distance down the barrel, allowing it to pivot. Also note, he doesn't need a long skinny indicator to reach down the barrel. Dave Kiff sells the rod that he is using. It takes reamer pilots on one end and is just barely into the tailstock chuck on the other.
 
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When both ends are indicate,to the bore, there is a plus for benchrest
shooters. That one barrel can be removed and another put in its place
seldom takes you far from the point of aim. Had the muzzle been on its own
in a spyder, its a guess. When you can change barrels and the first shot is
an inch off at 200, something is right. There not always that close, but
you know where they are.
 
To Whom It May Concern

One of the best Benchrest Shooters in the World, (and I do mean "the World") does his barrels by aligning the first 2-3 inches length of the barrel's ID dead true, and cares nothing for how the muzzle end is running.

When he does a barrel, it is a little strange to see that muzzle end running out, but the results speak for theselves....on the target.

..........jackie
 
When you drive into a tunnel you do not worry where the exit is, as it does not matter, hitting the entrance straight does. A bullet would be the same, the best chamber is the one that starts the bullet true to the entrance of the bore. Indicating the exit would be a waste of time. the bullet has to follow the bore.

From an engineering and a machining standpoint, the entrance is all that matters, no consideration about what the exit is doing would be taken.
 
I would think that when a barrel is drilled, There is some concern that the drill
comes out the middle at the other end. There is no doub't that an accurate
chamber can be done in a number of ways if its set up properly. I have never
been able to find a perfectly straight rod, .2366,.2368 and.2370 with no
taper and 6 inches long, so I don't have to move it when indicating. If I
could, I might try another method.
 
Bob

The big misscinception the ID'S of barrels is in how the "crookedness" manefests its self. Barrels are not curved, like banana. You might have one spot up in there that runs out one way, and just a few inches up in, might run out exactly the opposite. This is a product of how a Gun Drill can drift while doing it's job.

If you ever get a chnce, take an old barrel scribe a line down it, and then saw it up in 2 inch sections. The line will allow you to see the originol clocking of the OD. Then observe how the ID runs with these individule sections.

They will be off center in all different directions in relation to the scribe line........jackie
 
jackie schmidt said:
The big misscinception the ID'S of barrels is in how the "crookedness" manefests its self. Barrels are not curved, like banana. You might have one spot up in there that runs out one way, and just a few inches up in, might run out exactly the opposite. This is a product of how a Gun Drill can drift while doing it's job.


They will be off center in all different directions in relation to the scribe line........jackie
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Curved like a banana may not be the best analogy but I've designed and trouble shot enough gun drill setups to know that a gun drill can't just step over. If it did the drill would break. Granted, looking through the bore it may look like a step-over but it ain't. Most gun drills of the small bore barrel diameter (.35" or less) have a carbide section that is about 1/4"-3/8" long and carbide don't bend.

The drill however can wander in any or all directions as it goes through the barrel. i.e. It probably isn't just one smooth curve. Much of this wandering could be eliminated if the barrel maker would build a machine where the barrel and the drill both rotate. We've done this on 4140 shafts 48" long and the drilled hole was only 0.093?".

As to all this range rod/indicator rod business, if you use that method be aware that you are just indicating on the extrapolation of the curve.
 
JerrySharrett said:
Much of this wandering could be eliminated if the barrel maker would build a machine where the barrel and the drill both rotate..
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Hi Jerry,

How would the rotation of the barrel and the drill improve the bore straightness?

I would think the barrel material would see the same cutting edges, flute support, and speed rates, so I am having a hard time finding a difference that would achieve improved results.

About the only difference that I can think of with a rotating barrel and drill is possibly a more uniform stress and support situation, since neither would be in a static horizontal position, and/or better fluid flow distribution.

Wonder if any gun drills are used in the verticle position, to reduce gravitation sag and bowing/bending stresses?..............Don
 
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Don said:
Hi Jerry,

How would the rotation of the barrel and the drill improve the bore straightness?

Don
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Gyrostabilazation I guess? Ever notice how a center drill seeks the center of rotation? If there are two centers of rotation would there not be better stability? These are all just speculations and gut feels. I do know that in rotating both items the heat of machining, especially the chip and oil heat is spread around evenly instead of flowing downward and effecting just one side of the workpiece.

I do know also that when we made the dual rotation setup that the holes turned out straighter and the drills lasted much longer between regrinds. We stumbled into this not from trying to drill a straighter hole but to get the required SFM on the 3/32 drill since the spindle rotating the drill lacked quite a bit.

On this workpiece the drilled hole was just for compressed air which operated an air collet so hole straightness was not a functional requirement.
 
Don said:
Wonder if any gun drills are used in the verticle position, to reduce gravitation sag and bowing/bending stresses?..............Don
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Don, one more comment, High Standard Firearms was one of the pioneers of carbide tipped, high pressure oil, gun drilling. Matter of fact they did have some vertical drill setups. High Standard also marketed gun drills and rotary coolant couplings in the 1960's.
 
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Much of this wandering could be eliminated if the barrel maker would build a machine where the barrel and the drill both rotate.
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Jerry, I can see your point.
I can remember reading a book, im sure it was in the re-print, 'how rifle barrels are made' where early barrel makers found that when using a tip similar to a 'D' bit, actualy more like an off centre 'V' bit, and both the raw material and drill rotated, they ended up with straight/straighter bores. This was because the cutting face, if you were to cross section it, looked like a 'W' except that the centre of the 'W', called a nipple, was shallower, and because of this face profile the drill was always guided and stayed on its central axis rotating around the nipple. I hope this all makes sence! a little hard to explaine and put into words, but simple realy if only I had the book to hand, actualy thinking about it, I could have seen it in an old gun-drilling book but the same points apply.

Cheers

KB
 
Geez, I thought all the gun drills had counter rotation?

I'll have to run the traps on that one?

Ben
 
Ben

Bnhpr said:
Geez, I thought all the gun drills had counter rotation?

I'll have to run the traps on that one?

Ben
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Some or all of them may now. A few years ago not so. Douglas used to have a video on their web site but I can't find it now.

Check it out and let us know. It was in the 1970's when I was working on projects like deep hole drilling.
 
Some manufacturers that are still using the old P&W twin spindle deep hole drills don't have counter-rotation. The newer stuff mostly all has it. One or the other will be high speed rotation, 6000RPM and higher, and the other will rotate 200-600 counter rotation. I've looked into it a bit, and supposedly they DO drill much straighter holes.
 
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