Jerry Sharrett & Jackie Schmidt-- and others

L

Lucky Shooter

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I'm in the process of indicating a barrel per your "two point" method and have some questions.

I have a new 4-groove Krieger barrel in the lathe and am indicating at the throat with a long stem Interapid indicator----.0005" per division.

I'm indicating just inside the muzzle with a .0005" per division B&S indicator.

I'm presently indicating on top of the lands and have indexed the barrel in the chuck to have the lands pretty much centered with each jaw of the 4-jaw chuck. This indexing also holds fairly true with the screws at the spider end.

The throat---and ahead of the throat---has been easy to set up with very close to zero runout between the four lands.

The muzzle end is another matter.

I can set the runout between 2 opposing spider screws to zero but the runout between the other pair of screws is -.0005" and +.0005".

When I adjust runout between the .0005" screws to zero, the runout between the zero runout screws changes to -.0005" and +.0005".

In other words, I can adjust either pair of spider screws for zero runout but the other pair of screws will indicate -.0005" and +.0005".

In my mind, the muzzle end is centered symmetrically on the spindle axis but there will be a TIR of .001". Is this in line with your thinking ?

I think I've indicated the throat correctly and also think I've indicated the muzzle to the best this barrel will do with the muzzle at this particular point.

I haven't tried to relocate the muzzle and haven't tried to compromise between the zero and .0005" runouts.

I'm going to pause at this point and get advice on how to proceed from here.

Will appreciate any advice.

A. Weldy
 
I might be out to lunch here but I think if the muzzle is within a couple of thou or 2 ten thou it won't make any difference... the other end is so much more important...
 
i'm a novice, but pretty sure jackie's reply is that a couple thou is fine. remember it is the other end you are working on....how long is the bbl ? now think just how little it will influence the chamber xx inches away ?...go back to work on the chamber.

mike in co
 
Thanks Dennis and Mike

I thought this would be indicated in well enough but wanted to be sure.

I think this is about as good as can be done--by me--- with this particular barrel with these particular throat and muzzle locations.

A. Weldy
 
Something sounds suspicious. Are you checking the lands or the grooves. Insert a pin in the muzzle and see if you can dial it in then go back in and check runout inside the bore.
 
SamLS----

Thanks for the reply---took me a while to get back.

I'd appreciate knowing what is suspicious in this setup.

I'm using indicators inside the bore already----both ends simultaneously.

I've been indicating first on top of the lands and then on the adjacent grooves and showing a consistent difference of .003". This is an indication of the Krieger quality as they specify .224" and .218" land and groove diameters respectively.

As I mentioned, when I indicate at the throat, I get ZERO runout between between opposing lands. This tells me that the indicator is wiping a plane that is square to the bore axis and square to the spindle axis----and that the bore axis is coincident with the spindle axis at this point.

When I indicate the muzzle, I get similar but not identical conditions. The readings under opposing spider screws are equal to each other but not equal to to the readings under the other opposing pair of screws----this difference is consistently .0005". This tells me that my selected muzzle point is centered on the spindle axis----but not wiping a plane that is square to the spindle axis. In other words, the bore axis crosses the spindle axis at this point.

I think---unless somebody shows the error in my thinking---that this setup meets the objective, spelled out by Jackie Schmidt, for a "two point" setup.

I admit to being a raw beginner at this and have done a grand total of 2 barrels, both setbacks from old PD rifles. This is the first new barrel for me and I'd like to get it right, given following Jackie's "two point" method.

Please correct me if I've made a mistake----if its not too late. I've already turned the tenon and will thread when I can get back to the lathe.

A. Weldy
 
Weldy

You do remember that after I establish two points dead true, (the muzzle, and the throat), I then single point bore the third point, (the chamber), true with these, so that the reamed chamber will be dead true with the throat, and the muzzle. Al other machining operations are also machined true with these.
Why you can't seem to get the muzzle end as true as the chamber end is a mystery. It sounds like your barrel may be sliding in the opposing screws a little. Keep in mind, your screws have to be dead opposite each other, and the 4 screws exactly 90 degrees apart.........jackie
 
I've been gone for a few days, sorry. My suggestion is to indicate off the lands for the chamber end since that is where the reamer pilot rides. As to the muzzle end I indicate off the grooves and here's why. A knife sharp crown is easy to do and if properly done shoots great, But a knife sharp crown will not shoot as well as long as a crown with a slight bevel.

Remember Greg Wally's high resolution photos? The sharp crown is soon damaged by the cleaning process. Then it stops. A sharp, no bevel, crown does not have to be indicated but to about 0.002" or so to get a good job. This is why many professionals use this method. It works, and it saves time.

I take the time on the muzzle to indicate the grooves to where there is no readable runout. Then I cut the crown, finishing with a bevel that just is barely visible in the groove area. This makes a more durable and just as accurate a crown as does the knife edge crown.

Just speculating, average cleaning methods, a sharp crown will start to show damage in 100-200 rounds. A micro beveled crown will still be in good shape, inspecting with an 18X loupe, at 400-600 rounds.
 
jerry,
what angle is your crown bevel ?

thanks
mike in co
 
I just swing my crown finishing tool around to about 45 degrees. My finishing tool is a HSS/Co with a steep lip, steep heel clearance, and honed sharp. I rough the barrel end with a sharp piece of HSS/Co but not the razor edge the finisher has.

I swing the tool to about 45 degrees, clip on a 10X glasses magnifier and feed the tool out to where the bevel is just visible on the grooves area. That leaves the lands having about a 0.006" X 45 and the grooves about 0.003" X 45. That amount, IMO is not important as to size but there is no need of making a big bevel. Besides a big bevel looks like you have taken a countersink tool to it!!

If the bevel angle is too shallow it doesn't function as I want it to and if it is too steep, some old timers think a steep bevel may effect the exit of a boat tail bullet.
 
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Thanks for the replies

Jackie, I'm not sure what went wrong and exactly what corrected it. I tweaked the spider screws a little and the muzzle runout went down very close to zero.

There was no detectable change in the throat indication and the previously cut tenon was still true. After threading, the throat and muzzle still run true. There's
something to be said for a little luck now and then.

Again, I appreciate your help Jackie.

Jerry, thanks for the reference to the Greg Wally photos. I'd planned to cut an 11º crown----simple enough for a beginner.

A. Weldy
 
jackie,
whe you set back your bbls, do you recrown ?

thanks
mike in co
 
I prefer to indicate on the grooves myself, and bore the chamber concentric to the grooves. The bullet will center in the grooves not the lands. Sometimes there is a slight difference in the lands vs. the grooves.
 
One last question---I hope

I'm about finished with the breech end of this barrel and have what I hope is the last question on this thread.

I broke the corner at the mouth of the chamber with 3 different grits of emery cloth. Its no longer sharp and is very smooth.

Is this adequate ? I still have the setup and can do otherwise if necessary.

I've done my best to follow the steps recommended by several board posters and think the job is good at this point.

I followed the "two point" indication method and pushed the reamer with a floating pusher sleeve, held in the tail stock chuck. I took only a few seconds to coordinate the feel of the small Sinclair handle with the rate of feed.

This worked very well, IMO. There is essentially zero runout from the rear of the chamber up to well past the throat. The muzzle is still running very close to zero runout. The reamer is a tight fit in the hole---as some predicted--and the headspace is correct.

I'll cut an 11º crown.

Again, my thanks to all the board posters who've given me so much good info. I've learned a lot on this one.

A. Weldy
 
Lucky Shooter said:
I'm about finished with the breech end of this barrel and have what I hope is the last question on this thread.

I broke the corner at the mouth of the chamber with 3 different grits of emery cloth. Its no longer sharp and is very smooth.

Is this adequate ? I still have the setup and can do otherwise if necessary.

I've Again, my thanks to all the board posters who've given me so much good info. I've learned a lot on this one.

A. Weldy
Click to expand...
On a match chamber just getting the sharp edge off is enough. On this one you probably will not be able to see a broken edge, but it will not feel sharp.

For a hunting or magazine feeding chamber I'd say about a 0.003-0.005 radius. This one you can barely see.
 
Thanks Jerry

That's what I needed to know. I'll go ahead and finish the job.

A. Weldy
 
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