Has anyone experimented with the angled transition between chamber neck and freebore?

B

Boyd Allen

Active member
In the thread about bullets' pressure rings, there was some discussion of freebore and groove diameters. Has anyone considered that having a more gradual transition between chamber neck diameter and the freebore would have any advantage....or disadvantage?
 
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Boyd Allen said:
In the thread about bullets' pressure rings, there was some discussion of freebore and groove diameters. Has anyone considered that having a more gradual transition between chamber neck diameter and the freebore would have any advantage....or disadvantage?
Click to expand...

Ive only used the traditional 45 degree angle, but I have borescoped the transition of hundreds of barrels over thousands of rounds and what I have noticed is the transition area will pick up noticable carbon fouling but no copper fouling or firecrack erosion...............Don
 
Boyd Allen said:
In the thread about bullets' pressure rings, there was some discussion of freebore and groove diameters. Has anyone considered that having a more gradual transition between chamber neck diameter and the freebore would have any advantage....or disadvantage?
Click to expand...

IMO, it would simply make a bigger pocket to catch carbon. 10 degrees would probably better. A square shoulder would be too fragile for the reamer or the chamber.

Don, I would guess the flame temperature would be much less up close??
 
JerrySharrett said:
Don, I would guess the flame temperature would be much less up close??
Click to expand...

Maybe, I have never been able to figure out why firecracking is usually most prominent inches down the barrel from the chamber, you would think the bore would see equal pressures and temperatures, through out, at peak combustion pressure and therefore even firecracking through out, but that does not seem to be the case.
 
Don said:
Maybe, I have never been able to figure out why firecracking is usually most prominent inches down the barrel from the chamber, you would think the bore would see equal pressures and temperatures, through out, at peak combustion pressure and therefore even firecracking through out, but that does not seem to be the case.
Click to expand...

Interesting question. I would expect the highest pressure, temperature and duration of exposure to these conditions close to the chamber and decreasing toward the muzzle. Could it be that in the worst conditions, the surface is eroded away, farther forward merely cracked, and still farther, hardly affected at all?
 
Boyd Allen said:
In the thread about bullets' pressure rings, there was some discussion of freebore and groove diameters. Has anyone considered that having a more gradual transition between chamber neck diameter and the freebore would have any advantage....or disadvantage?
Click to expand...

Boyd, I am aware of one ornery lad (I say that affectionately) who is messing with a radius there . . . The jury will be out for a while though, as it will take a while to obtain meaningful data. :p RG
 
Don said:
Maybe, I have never been able to figure out why firecracking is usually most prominent inches down the barrel from the chamber, you would think the bore would see equal pressures and temperatures, through out, at peak combustion pressure and therefore even firecracking through out, but that does not seem to be the case.
Click to expand...

Don, on any powder there has to be a spot where it is at maximum burn and generating the most heat and I would guess that spot being just out of the cartridge. Plus, at that point the flame is very hot AND moving slow is it not?

What say there Houston, are a go!!
 
I have. No definitive information to pass on. There may never be much as that area gets gas cut so badly with larger capacity cases. I think that problem, if it is a problem in smaller cases can be addressed with design changes in another area.

Dave
 
Freebore

I think Boatwright did a article on this a while back and I had Dave Kiff do a reamer on his thoughts. Now in 7wsm and need the time to shot it.

Cheers
 
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