Chamber length

[Bruce Day]

Sometimes people get all excited about chamber length. Tests demonstrate that chambers 1/8 shorter than actual expanded shell length result in a pressure increase of 3 to 5%.

The SAAMI standard for nominal expanded shell length of 2 3/4" is from 2 5/8" to 2 3/4".
Shells from some manufacturers consistently run toward the minimum.

[Bill Murphy]

Yup, low pressure shells in guns with chambers shorter than the shells are no big deal. I am much more interested in the loads in the shells than I am in the length of the chambers compared to the length of the shells. Measure the wall thickness if you are suspicious.

[Researcher]

Here is the chamber depths and shell lengths from the Remington-era Parker specifications sheets reproduced on pages 163 to 167 of The Parker Story --



Chambers 1/8 inch shorter than the intended shell in 10-, 12-, 16- and 20-gauges and 1/16 inch short in 28-gauge and .410-bore.

[J.B. Books]

Originally Posted by Dean Romig

Were the 8 and 10 gauge chambers cut for brass shells or paper?

The 2 5/8" chambers were for 2 3/4" paper shells, allowing for 1/8" of the paper shell to open into the cone for a superior gas seal.


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I have owned 4 Short Tens, Parker, Remington, Lefever, from 1893 to 1905. The Parker from 1893 had square chambers, the others from 1900-1905 are tapered. All measured 2 7/8"

I still believe guns were chambered for a particular shell and marketing was used to tell the customer it could be used with another shell length and work just fine. I also think when it is difference of 1/8 inch collector/shooters fret too much about it in both directions (OMG my chambers are short, or OMG my chambers were lengthened). The focus should be on barrel wall thickness of each particular gun and shooting lower pressure loads when possible, but that is just me.

[Cold Spring]

I've been reading this 1/8" shorter stuff for years. Agreed, early American side by sides were generally not marked for chamber length and gents have been shooting 2-3/4" paper shells in 2-5/8" 12-gauge chambers forever. So, what were American 12-gauge 2-5/8" paper shells intended for ..... 2-1/2" chambers? What American guns were those? By maker and model please ...... ?

Yup I know that 12-gauge 2-5/8" shells were generally loaded up to 1-1/8 ounce, and 1-1/4 ounce was put up in 2-3/4" shells. So why not just use 2-3/4" shells for everything as is done today? To save the trees by the amount of paper used for that extra 1/8" of hull length?

Also, why did Savage routinely rechamber 12-gauge Foxes that were sent in for repair to 2-3/4" and reproof/stamp the barrels as such? If 2-5/8" chambers were intended for 2-3/4" shells, why not leave well enough alone?

Just some food for thought gents.

[Dean Romig]

I don't think there is any logical answer to these questions. The reasons for chamber length vs. shell length probably died along with the men who devised them.

Determining 'originality' may be the only good reason for measuring chambers these days, in view of the fact that none of us intentionally overload our old guns, either by length of cartridge or by the ballistics of the loads we use.






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[Researcher]

So, what were American 12-gauge 2-5/8" paper shells intended for ..... 2-1/2" chambers? What American guns were those? By maker and model please ...... ?

The main ones I can think of were the Winchester Model 1893 and the Spencer pumps. Here is a fairly light 12-gauge Parker Bros. made for 2 5/8 inch shells (sorry I didn't keep track of the original poster of this picture) --



I have seen record cards for Ansley H. Fox two barrel sets where the longer tighter choked set was ordered for 2 3/4 inch shells and the shorter more open choked barrels for 2 5/8 inch shells.

Also, why did Savage routinely rechamber 12-gauge Foxes that were sent in for repair to 2-3/4" and reproof/stamp the barrels as such? If 2-5/8" chambers were intended for 2-3/4" shells, why not leave well enough alone?

Probably lawyers!! That policy may have had more to do with 20-gauge guns originally chambered 2 3/8 inch intended for the 2 1/2 inch shells, and 16-gauge guns chambered 2 7/16 inch intended for the 2 9/16 inch shells.

[J.B. Books]

Dave did the 2 5/8" chamber proceed the introduction of 2 3/4" shells?

[Cold Spring]

The early 1-1/4 ounce 12-gauge loading (2-3/4") wasn't that popular before the introduction of progressive powders in the Super-X shell (1922) and its clones. That's because the earlier degressive burning powders like DuPont's Bulk and dense Ballistite and Infallible couldn't get all that shot moving in a hurry without deforming a large percentage of the pellets, and especially when restricted in a chamber that was 1/8" short. Hence it was known that the 2-5/8" 1-1/8 ounce load would perform about at par at distance, and with less recoil. I don't know about early Parkers but I've seen and measured many early Foxes in wildfowler configuration that have factory chambers measuring a full 2-3/4" - no doubt intended for what was then max long range performance with the period 1-1/4 ounce factory loads with degressive powders in 2-3/4" cases.

Regarding those Winchester 1893's and Spencer pump guns I have a hard time believing that 2-5/8" shells were being manufactured in quantity for a comparatively small number of them. And it would be nice to hear from someone who actually measured their chambers (or the ones ones in that Parker in the pic) to tell us if they are really 2-1/2" as per my earlier question.

Dave's comment on Savage lengthening 20 and 16 gauge chambers makes sense after small gauge shells were standardized at 2-3/4" but again, if 2-5/8" chambers were intended for 2-3/4" shells for that "tight gas seal", why was that done on 12-gauge guns? A rhetorical question gents .....

[Researcher]

Generally I've only researched from about 1891 when I find Union Metallic Cartridge Co. beginning to offer factory loaded smokeless powder shotgun shells. Looking at an 1884 UMC catalogue I see them offering brass 12-gauge cases from 2 1/2 to 3 1/4 inch length and paper 12-gauge NPEs from 2 5/8 inch to 3 1/4 inch. Going even farther back to an 1880 catalogue they offered paper 12-gauge cases from 2 5/8 inch to 3 1/4 inch. I don't have access to anything from the 1870s that shows shotgun cases but 1869 the just offered 10- and 12-gauge brass cases and no mention of length.