Chamber / Forcing cone

[stumpstalker]

Drew:

I get your point that “The cone can be lengthened (BY AN EXPERT, who is removing metal) while maintaining a wall thickness equal to the end of the chamber”. And those are very helpful graphics you provide to illustrate the result.

But would not GREATER, not equal, wall thickness tend to be called for when the reducing the area that a powerful charge has to travel in a tube? There is, after all, greater FORCE that is created and has to be contained by a “Forcing Cone”.

Even if lengthening the chamber is going to actually reduce pressures, as Bruce says, maybe by 300 psi, are these trade-offs feasibly calculable so as to determine net benefits when dabbling in invasive surgery on the most important part of any gun (the barrels)?

I know that this is a recurring topic and may well be tiresome for some. But since it relates to safety, i.e., the avoidance of maiming oneself and others, and can have consequences that risk besmirching the reputation of the entire sport, it is worth a solid understanding.

[Drew Hause]

Russ: a couple of very helpful graphs.

This from 1931 shows the pressure-distance curves with vintage powders; FFg, Ballistite (Dense) and Schultze & DuPont (Bulk) and DuPont Oval "progressive burning smokeless powder"



The pressure is falling at the forcing cone, though less so with DuPont Oval

Modern powders peak and fall much more rapidly so the pressure at the forcing cone is even lower



So there would be no safety justification for more wall thickness in the cone compared to the end of the chamber (where pressure is higher)

And to clarify Bruce's point, Bell's study compared 2 1/2” chamber with a 7/16” forcing cone vs. 2 3/4” chamber with a 1” forcing cone and showed the pressure decrease was about 400-1200 psi depending on the load and vv. the pressure rise could be as much as 1200 psi
A summary is here about 1/4 way down
https://docs.google.com/document/d/1...vwLYc-kGA/edit