Flat crown square to bore ?

[Lucky Shooter]

Edited to clarify question.

I've heard for a long time that the crown should be as close as possible to
square with the bore line at the muzzle.

For those who use two point indicating----throat and muzzle----do you make
another step to get the crown square to the bore center line----before setting
up to chamber and thread ?

Would appreciate knowing how others handle this.

A. Weldy

 

[Dusty Stevens]

Dial it in exactly the same as if it was a chamber- 2 points

 

[B Nettesheim]

Yes

 

[Alex Wheeler]

I've heard for a long time that the crown should be as close as possible to
square with the bore line at the muzzle.

For those who use two point indicating----throat and muzzle----do you make
another step to get the crown square to the bore center line ?

Would appreciate knowing how others handle this.

A. Weldy

You only get to pick 2 points to dial. You need to choose which section of the barrel those 2 points are in and how that effects accuracy. The word concentricity is often used too loosely, understanding what it really means may help the decision.

 

[jelenko]

Shouldn't the crown be square to the last part of the barrel just before the muzzle?

 

[SKWERLZ]

I indicate the area I’m working on and could care less what the other end of the barrel is doing.

 

[butchlambert]

I indicate the area I’m working on and could care less what the other end of the barrel is doing.

Really

 

[jackieschmidt]

Shouldn't the crown be square to the last part of the barrel just before the muzzle?

In an ideal world, yes.

if you are shooting a bullet with a 3/8 long bearing surface, the very last 3/8 inch or so of the barrel’s ID should be truly square with that.

Of course, I said in an ideal world.

 

[DaveTooley]

Really

Took the word right out of my mouth.

 

[DaveTooley]

In fact the crown, regardless of style needs to be perpendicular and in some cases concentric to the base of the bullet. An imperfect base at that. The escaping gas affects the base of the bullet much more than the body. I would say the bullet body does not play a role in this. A flat crown can be perpendicular to the base without being concentric. Though in reality we would never know it one way or the other since we can't control, with absolute perfection, the shape of the bullet base. We just get as close as we can and move on. If you've ever seen high speed video of muzzle gasses after a bullet exits a barrel you'll have a better understanding of what is happening.

 

[tobnpr]

Shouldn't the crown be square to the last part of the barrel just before the muzzle?

That's how I look it, where the bearing surface of the bullet is riding before it pops out of the muzzle.
I stick about 1/2" of a gage pin with a slightly snug fit (so there's no "wobble", but won't scratch the lands) and run an indicator on that.

I don't think it matters all that much (I don't care about a few tenths) compared to getting the chamber perfectly concentric so the bullet launches into/gets engraved into the rifling correctly.

 

[Kings X]

So an 11 degree crown is "square" to the bore?

 

[butchlambert]

So an 11 degree crown is "square" to the bore?

Richard, No, but why do a lot of folks think 11 Deg is magic.

 

[Kings X]

Oh I see this post is about "flat" crowns.
I think11 degrees comes for Hatcher Notebook on Navy cannon test.

 

[GenePoole]

I don't think it's magic, just that you'd like a little offset to protect the crown from banging into things. You could use a common machinist angle like 45° or you could cut it into 1/2 pieces like machinists like to do, such as 22.5° or 11.25°.

 

[butchlambert]

Oh I see this post is about "flat" crowns.
I think11 degrees comes for Hatcher Notebook on Navy cannon test.

Richard the 11 deg wouldn't hurt, but I personally cut mine perpendicular to the bore and then about after .150 I cut back on a 33deg for about a .050 depth leaving a flat to the edge. I hope you understand My description.

 

[DaveTooley]

So an 11 degree crown is "square" to the bore?

The edge in the groove and the edge at the top of the land is just that, an edge/line, regardless of the crown angle. It's important that an 11 degree crown be as concentric as possible because the ensuing edge won't be perpendicular to the base of the bullet if not concentric. The bullet will clear the bore ever so slightly sooner on one side. Now just to add some confusion to the discussion. How does the misalignment for a 90 degree crown compare with a nonconcentric 11 degree crown?

 

[Edd]

I only have hunting rifles but my favorite style of crown is one that Mike Bryant put on a couple of my barrels. The angle that contacts the grooves and lands is 60 degrees.

 

[SKWERLZ]

Really

If bores were perfectly straight I’d indicate both ends.
Most aren’t so I indicate an appropriately 3” area and then the chamber/throat or crown is perpendicular to the bore.

That said I think a few well known smith’s indicate the ends.

 

[butchlambert]

If bores were perfectly straight I’d indicate both ends.
Most aren’t so I indicate an appropriately 3” area and then the chamber/throat or crown is perpendicular to the bore.

That said I think a few well known smith’s indicate the ends.

Yes sir, we all do it the way that makes us warm and fuzzy.
So you have an indicator and probe that will reach 3" in the muzzle end accurately or do you use the Gordy method?