I found this among some 32-40 brass. Thought it was a nickel case until further investigation.

What are they used for? Go no go gauge?

The idea was to be able to use low powered revolver cartridges in your center-fire rifle for practice, plinking, etc.  They were made in several .30 and .32 calibers.

Ken Waters did a rather detailed article on them.  It is in his Pet Loads book.

I have a supplemental chamber for my .30 US that uses rimfire blanks and .30 cal lead bullets that you finger seat to shoot. I tried a few and found them reliable, but not so accurate in my ol' highwall. I have one of the Winchester versions but never tried it out.

Jeff that is what had me wondering as well and that being how would a .312 bullet work in the 32-40's .312 bore diameter. Mann has stated on occasion that bore diamter bullets proved to be more accurate than groove so it makes me wonder how well the Long Colt bullets actualy shot? Then again I don't understand fully how the case adapter actually worked so could someone please explain the entire process of it's actual use.

I also understand Marbles made them as well. I believe I saw a display on them at a collectors show many years ago and thought it was an interesting idea.

Flatlander

BP wrote on Mar 9^th, 2017 at 6:56pm:


Not likely--it's retained by a screw.  Never had one (though I've always wanted to try one out), but there's a cross-sectional drawing in my 1905 Marble's catalog.  It's actually called "Brayton's Auxiliary Cartridge."

By positioning the bullet at or near the origin of the rifling, accuracy ought to be better than with the other design, though probably not great in either case.  But not much was expected, as the idea was to use them for pot-shooting small game while hunting big game, like fool-hens perched on a limb a few yards away.

Bullet diameters and base cavities?

BP wrote on Mar 9^th, 2017 at 7:50pm:

  Yeah, go ahead, I'm all ears.

I used to have a small collection of those cartridge adapters in Marbles and Winchester. The Winchester ones were tough to find, as I figured Winchester collectors grabbed them up quickly. Some worked pretty well, while others were pretty poor accuracy.

These supplemental chambers, whether Winchester or Marbles, are in my experience quite uncommon.  And while Winchester examples, no surprise, generally sell for a little more, clean, usable examples (which for Winchester refers especially to the plating) are generally offered for $25-$40 each.

If you just want to try such an accessory, a large number of new-made chambers are available from MCA Sports & CE Bullet Co.; there web site is (You need to Login or Register to view media files and links).

Bill Lawrence

Sold mine years ago for $10 each, but last I saw were around $25-$30 for nice clean ones.

One exactly like that one sold last nite on ebay.  I quit watching it at about $38.00.  Already spent my allowance on more important stuff.
James

Was the seller providing any outside-lubricated Short or Long Colt to go with it?

By accident ran across a review of supplemental chambers in the 5th ed. Gun Digest Treasury.  A Marbles chamber tested in a .30-30 produced 3-shot groups of 1" at 25 yds.; but as the author stated, hitting a grouse at that range was all that was expected.  Best of the devices appeared to be one made by RWS similar to the Marbles with its own spring-loaded firing pin.   

I live where there are fair grouse populations, and a few times I've encountered one that loitered long enough to make itself a good target, assuming the chamber was loaded and ready to fire.  But 99% of them flush without my even seeing them, so instead of a supplemental chamber, a can of sardines might be the hunter's wiser choice.

Redsetter wrote on Mar 26^th, 2017 at 3:40pm:

Get a dog to keep the bird's attention focused away from you so you can get closer?