W.A. King on forcing cones

[Rick Riddell]

So based on the aforementioned above, the chamber, forcing cone and bore were designed to to shoot a longer shell to produce an idea chamber pressure and patterns when shooting Parkers during that time frame, but as innovation and technology changes it's probably not best to shoot modern longer shells in them? Do I have that right? Has anyone patterned longer shells in shorter chambers vs shorter shells?

[Drew Hause]

This is the 1907 Hunter Arms Chamber Specification

Forcing cones are slightly less than 1/2". The cone angle was shallower in the 1935 drawings with a length of about 5/8".



The forcing cone appears to be cut straight, BUT this is a Cerrosafe chamber and forcing cone casting, and there might be a slight Ogee



I have an Ithaca Specification drawing from 1935 kindly provided by Walt Snyder, which also shows a straight forcing cone angle

[Drew Hause]

Here you go Rick.

“Long Cartridges in Short Chambers”, Field, Jan. 30, 1892
https://books.google.com/books?id=in...page&q&f=false
2 1/2” chamber 12g
3 Dr. “E.C.” with 1 1/8 oz. shot in 2 1/2” case 1” pressure – 5,475 psi by LUP (+ 10-14% for modern transducer numbers)
3 1/2 Dr. with 1 1/4 oz. in 2 1/2” case – 6,200 psi
3 1/2 Dr. with 1 1/4 oz. in 2 3/4” case – 6,600 psi

“Mr. Griffith on Shotgun Patterns”, 1897 Lecture
https://books.google.com/books?id=in...page&q&f=false
p. 243 “Turnover” - case longer than the chamber
No. 9 2 1/2” case with 1/8” turnover
No. 10 3/8” turnover
No. 11 & No. 12 with 2 3/4” and 3” cases in 2 1/2” chambers = “…patchy patterns, clustering, and frequent balling…” Pattern examples on p.244
p. 245 “balling or clustering”
p. 247 Summary of patterns; Field, March 5, 1898
No. 9 - 1/8” turnover better pattern % than 10, 11 & 12

Pressures with 3 Dr. “Schultze” with 1 1/8 oz.
No. 9 – 2.13 tons = 6,040 psi (converted by Burrard’s formula)
No. 10 – 3.03 = 9,060 psi
No. 11 – 3.22 = 9,700 psi
No. 12 – 3.71 = 11,345 psi

“When long cases are used in short chambers, the paper overlaps the cone and causes greater resistance to passage of the shot and wads. The pressure then goes up considerably, while muzzle velocity and recoil are both increased.”

We all understand the studies used (thick) paper cases; not modern plastic cases and polyethylene wads

[Rick Riddell]

Once again Dr.D you are a wealth of information! Thank you very much for what you do and share!

[Paul Harm]

Why hasn't anyone brought up reason of only 1/2" forcing cones was because the fiber wads were only about 5/8" - 1/8" OP card and 1/2" cushion wad. With a 1/2" forcing cone the pressure was contained with less blow by. Maybe the over lap also helped seal things along with a slight pressure spike.

[Drew Hause]

Paul: starting on p.238 Mr. Griffith reported on loadings with various wads; soft vs. hard; thick vs. thin

[Drew Hause]

OTOH, and I have no idea what Bro. Bruette is saying

Dr. William A. Bruette, Guncraft: Guns, Ammunition, Wing & Trap Shooting, 1912 (Editor of Forest & Stream)
https://books.google.com/books?id=5g51K93as84C&dq

“Cause of Bad Patterns”
https://books.google.com/books?id=5g...4C&pg=PA100&dq
The most general cause of bad patterns is tightness at the nose of the chamber, whereby the exit of the charge is impeded, and the pressure of the powder is accordingly increased. When the chamber is right and the shooting is bad the next thing to examine is the form of the cone joining the chamber to the 12-bore part of the barrel. This should be of not greater length than .25 of an inch, and the slope should be a true taper from the nose of the chamber to the barrel.
When the cone is excessively long the column of shot is apt to widen so as to occupy the greater diameter beyond the cartridge. Its subsequent compression to the diameter of the bore jams the pellets together, so causing a tendency to ball, or at any rate to deform them so as to interfere with their regular flight after leaving the muzzle.

[Dean Romig]

Originally Posted by Drew Hause

When the chamber is right and the shooting is bad the next thing to examine is the form of the cone joining the chamber to the 12-bore part of the barrel. This should be of not greater length than .25 of an inch, and the slope should be a true taper from the nose of the chamber to the barrel.
When the cone is excessively long the column of shot is apt to widen so as to occupy the greater diameter beyond the cartridge. Its subsequent compression to the diameter of the bore jams the pellets together, so causing a tendency to ball, or at any rate to deform them so as to interfere with their regular flight after leaving the muzzle.

Hmmm... Seems we’ve read the same thing about chokes going abruptly from the 12 bore barrel to the cone of the choke and that’s why Parker’s chokes are cut ogee (ogive).





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[Joe Graziano]

In the “newer” guns, I use 2 3/4 in shells and have had zero problems. I simply keep them to 2 3/4 dram equivalent. In the lifter, I use the incredibly light AA low noise, low recoil loads. All seem to work well for me.