Muzzle bore alignment question

[Ken Worth]

In a recent thread there is the mention of muzzle alignment when cutting a chamber. Question, how do you line up your muzzle bore when cutting a chamber?

[Al Nyhus]

Ken, are you asking about the bore relative to the o.d. of the muzzle? -Al

[Ken Worth]

Originally Posted by Al Nyhus

Ken, are you asking about the bore relative to the o.d. of the muzzle? -Al

Nope. What would the OD ID relationship of the muzzle have to do with accuracy? What I am asking is if gunsmiths generally think it is important that when the chamber area is dialed in, is it important to accuracy that the muzzle BORE be in alignment also. Simply put when you screw on a barrel, should the muzzle bore point in the same direction that the chamber, action and stock point.

[wnroscoe]

Ken,

While there are numerous ways to chamber I prefer to work on one end of the barrel at a time. I dial in the breech with a PTG Range Rod using a Four Jaw Chuck and an Outboard Spider. I indicate at two points along the Range Rod and let the muzzle run as it will during the breech machining. When I cut & crown I spin the barrel around, dial the muzzle in and let the breech run as it will. My headstock is short enough that the barrel sticks out both ends during these operations.

[jackie schmidt]

You will find that there areas many different ways to align a barrel for chambering as there are .300+ aggs at Tomball.

Seriously, some shooters align the first couple of inches of the ID at the chamber end, using a chuck at or some other turing method, and a spyder at the muzzle end, and could care less what the muzzle end is doing. This is to insure that the chamber and all other subsequent machining operations are at least dead in alignment with that part of the barrel.

Others indicate the muzzle end, pre-drill the chamber end, and reach up in there where the throat will be established, and indicate that point dead true. They then pre-bore to establish a third true point, and ream. I use this method, with a few of my own ideas. The theory behind this method is if something is not dead straight, you can only establish two truepoints. You can, howerver, establish a third true point, (ie, the chamber), by single point boring it dead true with two predetermined points.

Some use a steady rest, chucking on the muzzle, establishing a true spot on the chamber end while running on center, and do all of the operations in steady rest. The drawback of this method is you have no way of establishing the chamber with what's encountered up in the barrel once you establish that steady rest spot. But, that being said, there have been a lot of championships won with barrels done in this method.

Some simply chuck the barrel up in a three jaw, (using some method of truing the muzzle end), use a floating reamer holder, and settle for what comes out.

If the ID of barrels were perfectly straight, all of this would be a moot point. But, since there are all sorts of anomalies up in there, you have to figure out a way to staisfy your standards............jackie

[Al Nyhus]

Originally Posted by Ken Worth

Nope. What would the OD ID relationship of the muzzle have to do with accuracy? What I am asking is if gunsmiths generally think it is important that when the chamber area is dialed in, is it important to accuracy that the muzzle BORE be in alignment also. Simply put when you screw on a barrel, should the muzzle bore point in the same direction that the chamber, action and stock point.

Ken, I think it's important that the spot with the most muzzle O.D. runout is 'clocked' to either the 12:00 or 6:00 position when the barrel is tightened to the action. -Al

[Jay, Idaho]

If the method used lets the muzzle end "run wild" during chambering, you better be sure that the muzzle is pointing uphill when installed on the barrel. If it is pointing downward and it is a 1000 yard BR rifle, you may need rings and bases that give you a lot of "come up".
If the muzzle ends up pointing L or R, you can run out of windage rather quickly.
This may not be a problem at 100/200 with 21" barrels but at 1k with a 30" barrel you can have problems.

Opinions by Jay

[Butch Lambert]

I've tried the range rod method and it sucks. After you indicate it in, take it out and try reindicating it. You will get a different reading.
Butch

[bigbull]

Originally Posted by Butch Lambert

I've tried the range rod method and it sucks. After you indicate it in, take it out and try reindicating it. You will get a different reading.
Butch

Butch, is this due to a loose fit of the range rod?
bigbull

[Bnhpr]

Originally Posted by Butch Lambert

I've tried the range rod method and it sucks. After you indicate it in, take it out and try reindicating it. You will get a different reading.
Butch

Butch +1

Looks good on the video....in practice it's too sloppy for me.

[Shooter53]

Ken Worth,

To indicate both ends of the barrel requires that the barrel is long enough to protrude far enough out both ends of the headstock of your lathe.

I set the chuck end in a live center mounted in the tailstock to get a rough center. I then close down the four jaw chuck until the jaws just touch the barrel. While rotating the chuck by hand I progressively snug up each of the jaws. At this point the barrel will be somewhat in line to the centerline of the bore (only somewhat!). I then snug up the spider chuck bolts on the muzzle end the same way. Now you are ready to start indicating the bore.

I place a range or indicator rod in each end of the barrel's bore. I then set up a 0.001" dial indicator on each rod indicating within 1 inch of the barrel ends.
At this point you'll need a lot of patience the first couple times but you'll get faster the more you practice.

I first indicate the end protruding from the spider chuck using the adjusting bolts to cut the indicator swing in half each time. I do this until I have 0.005 to 0.010" accuracy. I then move to the 4 jaw chuck end and do the same thing. No you're getting close! Go back to the spider chuck an indicate deflection down to 0.001" or less. Then do the 4 jaw chuck.
Finally indicate both ends until there is no perceptable movement on either indicator.

At this point the bore is running perfectly ( <0.0005" runout from one end to the other).

Of course I'm only using high end match or select match grade barrels so I have no reservations as to the barrels specifications ( more accurate than I can measure internally).

Now you are ready to start the breech work and everything will be cut concentric to the centerline of the bore ( the entire bore not just a small portion) and that spells accuracy.

After some practice I've got to the point where I can indicate a barrel to <0.0005" in about 15 minutes.

Hope this answers some questions. Again there are numerous ways to set up and I by no means wish to imply this is the best way, this is how I indicate both ends of a barrel to ensure everything is concentric to the bore.

Butch,

I tend to agree with your comment on removing the rod and getting a different reading upon re-insertion. I had the same problem until I started using the caliber specific indicator rods with the interchangeable pilot bushings.

[Bob Kingsbury]

It is quite rare, more like never that the od and Id are near parallel, at the chamber end. So when the 4 jaw is tightened and the spyder is indicated,
there is every possibility that you can be flexing the barrel. I use a soft
brass or copper sleeve,which is split and no more than an inch long. Approx
.062 thick. This is very forgiving, but holds well. Ferris Pindel told me to use
o-rings. My spyder won't adjust on o-rings so soft copper was it. Annealed
brass is fine and Aluminum would be ok also.
The peach chardonnay is great tonight, so I have to tell this.
The first barrel I ever chambered saw no dial indicators at all. I turned
a short area at the muzzle with live center in the tail stock. This was turned
at the tail stock. Turnining the barrel around, a cut was taken off the chamber end. While the muzzle was driven with a 3 jaw chuck. it was fairly
true. Tennon was cut and then chambered in a steady rest. Once cases were
formed, I was off to the range. A few shots close to sight in then up to 200
the first 4 were in .200 and #5 sat out by .100. What else could it be, but
a crooked chamber. SO__, I did it all over again. Still no wind flags.
Well I spent a lot of time getting this very close and the first group was worse. That was thirty years ago

[Ken Worth]

Originally Posted by Shooter53

Ken Worth,

To indicate both ends of the barrel requires that the barrel is long enough to protrude far enough out both ends of the headstock of your lathe.




After some practice I've got to the point where I can indicate a barrel to <0.0005" in about 15 minutes.

Hope this answers some questions. Again there are numerous ways to set up and I by no means wish to imply this is the best way, this is how I indicate both ends of a barrel to ensure everything is concentric to the bore.

Butch,

I tend to agree with your comment on removing the rod and getting a different reading upon re-insertion. I had the same problem until I started using the caliber specific indicator rods with the interchangeable pilot bushings.

Shooter53, thanks. This is what I am looking for, a muzzle dialed in with the chamber. Question, if you screw this barrel on an action and zero it, then screw on another barrel chambered this same method, about how much off is the POI on this second barrel from the first?

Butch, thanks also. (and thanks to all)

Bob Kingsbury, peach chardonnay sounds delicious, but you lost me on your last 3-4 sentences. Can you clarify "getting it very close". What very close?

[Shooter53]

BOB,

I understand about the flexing of the barrel. There is some out of round between the O.D. and I.D. of the barrels I use but it is extremely small. If I find one that concerns me I will true up the O.D. on both ends to the bore before chucking up for indication.

I think the first gun I did about 15 years ago was for my son ( 308 ). I'm still amazed because I just threw the barrel in a 3 jaw chuck and built a home made spider for the outboard side of the headstock just to hold the barrel from flopping around. No indicating of the bore no DRO at the time. And this was done on a Smithy 1220 combo machine that later I learned had 0.003" rundout on the 3 jaw chuck alone. The machine had about 0.008" of backlash on the carriage. I will say I took my time and did a lot measuring before a cut was made. Took the gun to the range and it shot consistently in the high 2's and low 3's still does to this day.

Just goes to show even a blind squirrel will find an acorn once in a while.

Of course I use Shilen barrels unless someone asks for something different.

Everyone has to start somewhere!

KEN,

Have not had the opportunity to test what Bob K. said about barrel swapping.
By the time I see a weapon again, typically it's just the barreled action so I have no idea where it is shooting. As for my son's 308 mentioned above it still has the same barrel. But what Bob was saying makes sense to me.

[Bnhpr]

Originally Posted by Shooter53

Butch,

I tend to agree with your comment on removing the rod and getting a different reading upon re-insertion. I had the same problem until I started using the caliber specific indicator rods with the interchangeable pilot bushings.

That's a tapered PTG indicator rod, a very different animal vs the range rod?

I thought we were talking about range rods?

The ptg indicator rods are great for rough alignment, I've even chambered some hunting rifles with them also.

Put one in with 2 dial indicators after rough drilling the chamber, then push a little sideways on them. Check your indicators, and they will be off >.001" and often >,003"

They are not repeatable either.