Response to jerry.....from the barrel poll thread...

jerry said:

Shilen Poylgon.

Click to expand...

___________________________________


Friend jerry:


I've had tremendous success with the Shilen octagon...

Here's the most successful octagon barreled RFBR rifle in history.



______________________


The problem with the octagon, is that it is very difficult to fit, properly.

And finding one that has been properly taper lapped is most difficult.



Not only does the octagon require an absolute perfectly centered chamber, the leade engraving length is extremely critical, more so than for any other rifling design I've ever worked with.


The octagon's chamber leade length is determined by the groove diameter at the breech, caused the the taper lapping.


The larger the groove diameter the greater the leade length can be, and vice versa....


As an example, a groove diameter of .2220" at the chamber, can use a full .150" of leade engraving...


Based on using a straight, .225" diameter chamber with 2 degree leade...


A groove diameter of .2218" at the chamber, for instance, must have a leade length of no more than .142", and so on.


Finally.................


Post chamber lapping is really needed for the octagon......

Of all the rifling patterns I've ever fooled with, the octagon must have a 100% fluid transition from the chamber, through the leade and into the bore.


So the difficulty of properly fitting the Shilen octagon, along with finding one that is properly taper lapped, means that it probably will never be "The barrel of the future".


Your friend, BC

tentoten said:

Mr Calfee,

Do you have pictures, you can post here and comment, of perfect chamber (the transition through the leade and into the bore) of Muller and Shilen barrels ?
I ask you that because I had a look at my different barrels with a borescope.
My best barrel has tools scratches in the leade area.
My other barrels have shiny chamber and very clean leade, but they don't shoot as good.
Crowns are pristine on my rifles, so I don't think the different can come from this side of the barrel.

Regards

Click to expand...

tentoten said:

"If you "seriously" believe the tool scratches are what's making your good barrel shoot".

I don't put it that way. But I don't mind your joke.

Don't forget I look in a borescope and imperfections are magnified many times.
Plus, when I pass a patch through the barrel I don't feel any scratches or roughness in the leade area.

What I have in mind is more this way :
My chambers without noticeable tools marks look perfect to the eyes but might have suffered from over lapping. I don't know how to tell.

However, I know what my chambers look in a borescope.
And I wonder what a perfect transition (chamber to the bore) looks in a borescope.

That's all folks

Click to expand...

__________________________________________


Friend tentoten:


There's no way I'd stick a bore scope in the chamber of this rifle to take a picture of the chamber/leade.





That is if I owned a bore scope, which I do not.


Actually, that was kind of a mute statement, cause if I came close to Black Death with a bore scope Big Dog would set me straight.....


Friend tentoten, maybe someone else here at CYA can furnish you a picture.


Your friend, BC