The history and science of short chambers

[Pete Lester]

I found two articles written by A.P. Curtis in the American Rifleman magazine. The first article "The advantages of short chambered shotguns" can be found on page 14 of the July 1936 edition. His second article can be found in the March 1938 edition on page 21 "The advantages of short chambered shotguns - Part 2".

Interestingly enough it was in 1937, in between these articles, is when SAAMI met and established chamber standardization along with its strong warning about the dangers of composite barrels. Was his first article the impetus for the 1937 SAAMI meeting?

What I took away from it, several manufacturers were producing guns with chambers 1/8" to 1/4" shorter than the intended shells along with the advent of the 3" 410 being shot in 2.5" chambers. This was done not for a better gas seal, but for less disturbance to the pellets entering the forcing cone. This was proven to improve patterns as the paper shells provided a cushion and seal as the pellets met the constriction of the bore. He cites some championship trap shooters who were using 3" target loads in 2 3/4" chambered guns. Longer shells in shorter chambers was not recommended for composite barrel guns. They could also cause a problem with early ejector systems. A nominal increase in chamber pressure of about 500 psi would result.

The two articles are a very interesting read and explain away any debate and mystery about short chambers.

Both articles can found and read here:

https://onlinebooks.library.upenn.edu/webbin/serial?id=amerrifle&fbclid=IwZXh0bgNhZW0CMTAAAR2TGAkWbq3snhh7HMlF3kw6Z vDGFLyt-nSDXbZJIsNwdwmJN5tOFDTeZe4_aem_Af_c1mPXdKOVQx6fks-LW4mC4DSqLt7-mL9J3lBlYR6SZTC3VYvmG6a6G_TBl3TmwaKnRlvpyYWq1WBiaF hpps7M

[Arthur Shaffer]

Keep in mind that at the time of the work there were no plastic wads or shot cups. The extended shell basically provided a soft instead of a metal forcing cone. This is the very reason plastic wads and shot cups were developed, proving the work's validity. For the vast majoroity of shooters now, it is no longer an issue.

[Pete Lester]

Keep in mind that at the time of the work there were no plastic wads or shot cups. The extended shell basically provided a soft instead of a metal forcing cone. This is the very reason plastic wads and shot cups were developed, proving the work's validity. For the vast majoroity of shooters now, it is no longer an issue.

I would say plastic wads were developed to make the mass production of shotgun ammunition easier. My point in sharing this is to demonstrate short chambers did not result from changes in ammunition length, it was deliberately done for better performance.

[Arthur Shaffer]

I'm sorry but I don't see that resultant conclusion. It is very possible that the original article may have instigated the SAMMI bulletin, but there is nothing I see in the articles that seems to say that they were promoting the concept of short chambers to improve performance. His own experiment, which apparently the ammo companies didn's do, was pretty statistically inconclusive. My take away from the articles was that they warned against shooting long shells in short chambers, and the ammo companies made ammo to be safe in the existing chambers. All liability driven.

The short chamber issue was just something that worked itself out on the side of safety with shorter shotshells to always be safe in the chamber. The performance increase he predicted was relatively small with variation in data large over each 8 shots.

Plastic shot cup wads certainly made loading easier I would guess, but I am old enough and was interested enough to read a lot early in life to remember the press and advertising about shotgun shell performance accompanying the development and introduction. There is no doubt that the ammo companies had performance improvement in mind when developing shot cup wads. It was an order of magnitude more than the sketchy data he obtained and is obvious to any shooter who loads both ways.s

[Pete Lester]

I'm sorry but I don't see that resultant conclusion. It is very possible that the original article may have instigated the SAMMI bulletin, but there is nothing I see in the articles that seems to say that they were promoting the concept of short chambers to improve performance. His own experiment, which apparently the ammo companies didn's do, was pretty statistically inconclusive. My take away from the articles was that they warned against shooting long shells in short chambers, and the ammo companies made ammo to be safe in the existing chambers. All liability driven.

The short chamber issue was just something that worked itself out on the side of safety with shorter shotshells to always be safe in the chamber. The performance increase he predicted was relatively small with variation in data large over each 8 shots.

Plastic shot cup wads certainly made loading easier I would guess, but I am old enough and was interested enough to read a lot early in life to remember the press and advertising about shotgun shell performance accompanying the development and introduction. There is no doubt that the ammo companies had performance improvement in mind when developing shot cup wads. It was an order of magnitude more than the sketchy data he obtained and is obvious to any shooter who loads both ways.s

Given the title of the articles I will have to agree to disagree on the point he was trying to make through examples and his mention of several gun makers who believed it made a difference and built their guns accordingly. The most important takeaway is why guns were made with short chambers.

[Dave Noreen]

I've been posting this information for at least three decades --

"In the book The Parker Story the Remington vintage specification sheets on pages 164 to 169 call for a chamber 1/8-inch shorter than the shell for which it is intended. Also, in the 1930's there were a couple of articles in The American Rifleman (July 1936 and March 1938) on the virtue of short chambers. A series by Sherman Bell in The Double Gun Journal showed no significant increase in pressure from shooting shells in slightly short chambers. .....

Also, Askins mentions (Modern Shotguns and Loads, 1929) that for the last 3 years or so the US makers started to hold their chambers shorter since the constriction made when shooting 2-3/4" loads in 2-5/8" chambers was found to improve patterning."

[Pete Lester]

I've been posting this information for at least three decades --

"In the book The Parker Story the Remington vintage specification sheets on pages 164 to 169 call for a chamber 1/8-inch shorter than the shell for which it is intended. Also, in the 1930's there were a couple of articles in The American Rifleman (July 1936 and March 1938) on the virtue of short chambers. A series by Sherman Bell in The Double Gun Journal showed no significant increase in pressure from shooting shells in slightly short chambers. .....

Also, Askins mentions (Modern Shotguns and Loads, 1929) that for the last 3 years or so the US makers started to hold their chambers shorter since the constriction made when shooting 2-3/4" loads in 2-5/8" chambers was found to improve patterning."

Until yesterday I had never found the articles to read for myself, I thought others would find them interesting.

[Bill Murphy]

Give me a direct link to the articles you reference and I will read them and comment. Curtis is one of few authors in the early days that didn't rely on "old wive's tales" to sell articles.

[Pete Lester]

Give me a direct link to the articles you reference and I will read them and comment. Curtis is one of few authors in the early days that didn't rely on "old wive's tales" to sell articles.

Bill it requires a little work to read them but it's fairly easy. Click on the link in my first post (posted again below), then click the year for the magazine, then click on the month of the magazine and it will open. Then you have to go to the page it's on which is in the index of the magazine.

https://onlinebooks.library.upenn.edu/webbin/serial?id=amerrifle&fbclid=IwZXh0bgNhZW0CMTAAAR2TGAkWbq3snhh7HMlF3kw6Z vDGFLyt-nSDXbZJIsNwdwmJN5tOFDTeZe4_aem_Af_c1mPXdKOVQx6fks-LW4mC4DSqLt7-mL9J3lBlYR6SZTC3VYvmG6a6G_TBl3TmwaKnRlvpyYWq1WBiaF hpps7M

[Mike Franzen]

If Bill can figure that out he would prove he could figure out how to post pictures

[CraigThompson]

If Bill can figure that out he would prove he could figure out how to post pictures

Damn you beat me to it :rotf: But I prefer to believe the one in question doesn’t want to post pictures period .

[Drew Hause]

Direct link to the article
https://archive.org/details/sim_american-rifleman_1938-03_86_3/page/20/mode/2up

Scroll down about 1/3 here for more information, including a 1897 study & Charles Askins quoting W.A. King.
The issue seems to have been "overlap"
https://docs.google.com/document/d/1ZIo0y746UsSRZIgRuuxwAbZjSBHitO_EanvwLYc-kGA/edit

(All you have to do is L click your mouse thingie on the link Bill :rolleyes: )

[Randy G Roberts]

Try this for easier reading, maybe.

[Arthur Shaffer]

I still think it is a question of chicken and egg. Following the thought process here, chambers were 2-1/2"; ammo makers lengthened shells for more performance to 2-3/4"; someone ran some cursory tests with pretty little data collected and pronounced the that long shells in a shorter chamber gave better performance; gunmakers after bragging rights decided to shorten the chambers to take advantage of that performance; ammo makers shortened their new shells to stay safe.

That's a lot of changes with little real data and even less factual proof that is what happened.

What is true is that in a later era with the proven performance of one piece cup wads, performance was elevated to an entirely different level and then improved again by modern design of barrels with long forcing cones and overbored barrels (which shouldn't even work based on the original theory). Trap shooters led the way and today no one builds a high performance shotgun without those features. The same features worked just as well before the plastic cup wads. Look at the work done by Becker and others and the legendery performance of the NNID Ithaca 10's and the Super Fox. The Parker was ahead of the times and normally used overbored barrels in their 10 and 12 guns, many of which performed very well with cylinder bored barrels.

The fact is that a long forcing cone with it's very shallow taper gives a smoother transition and the overbored barrel drastically reduces the effect of scrubbing on the shot column.

The proposition might make for an interesting history discussion (although proven details are nebulous) but they are neither here nor there as far as modern performance is concerned. Shoot appropriate shells the same or lesser length than the chamber and loaded with modern components, and everything will work well.

[Drew Hause]

Not everyone is convinced that bore size or forcing cone length matters; including Neil Winston
https://www.trapshooters.com/threads/back-bore-forcing-cone.365553/page-4

Neil Winston “Have Today's Increased Bore Sizes Improved Trap Gun Performance?” 2016
https://web.archive.org/web/20180829043517/http://claytargettesting.com/Bore_Diameter/Bore_Diameter.pdf

And for a historical perspective, the chamberless Tolley "Altro" was introduced in the mid-1890s
https://books.google.com/books?id=BFRDAAAAIAAJ&pg=PA31&lpg
https://books.google.com/books?id=Bzo6EAAAQBAJ&pg=PT92&lpg

Dr. Charles J. Heath chamberless patent
Forest & Stream July 1921
https://books.google.com/books?id=x1nlAAAAMAAJ&pg=PA308&lpg

1922
Sporting Firearms of Today in Use
https://books.google.com/books?id=9XMCAAAAYAAJ&pg=PA95&lpg

Field & Stream, August 1922
https://books.google.com/books?id=XQQ-AQAAMAAJ&pg=PA470&lpg

A few Lefever have been documented with "Taper System of Boring"; gradual constriction from end of chamber to the muzzle.
Forest & Stream 1909 "First to adopt the taper choke system."
https://books.google.com/books?id=l0kcAQAAMAAJ&pg=PA395&lpg

Charles Askins on "taper choke" in October 1917 "Recreation"
https://books.google.com/books?id=gX87AQAAMAAJ&pg=RA1-PA210&lpg

https://photos.smugmug.com/US-Makers/Lefever/i-CvBQDsN/0/5mKZqrhc8DjFKvhnv8T9xpJtqjdsrFZx5R2KPPzR/L/Lefever%20boring%203-1916%20Forest%20%26%20Stream-L.png (https://drewhause.smugmug.com/US-Makers/Lefever/i-CvBQDsN/A)

Daryl Hallquist has confirmed that an occasional Lefever 12 gauge has bores tapering from the breech to the muzzle (.756 to .708 left and .715 right on one gun). Most have a standard U.S. .729 - .732" parallel bore.

[Drew Hause]

Actual performance testing as opposed to marketing hyperbole

Jim Eyster 2010
http://www.jimeyster.com/testing/documents/Forcing%20Cone%20Test.pdf

Matt (discusses increased volume post-cone lengthening)
https://www.trapshooters.com/threads/the-effect-of-lengthening-forcing-cones-on-fps-and-possibly-recoil.895147/#post-8585555

[Drew Hause]

Sporting Guns and Gunpowders: Comprising a Selection from Reports of Experiments, and Other Articles Published in the “Field” Newspaper, Relative to Firearms and Explosives, Volumes 1-2, 1897, “The Junction of the Chamber and the Bore”
https://books.google.com/books?id=inQCAAAAYAAJ&pg=PA303