doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com 2 3/4" in a 2 1/2" Chamber

It has been noted in this discussion that American manufacturers often chambered short even though longer hulls were in use. I find this typical hang tag from Parker to be quite informative. Look at the chamber length and then the recommended shell. And these were from the days of thicker paper hulls. Today's plastic hulls are much thinner, offering even less constriction in the forcing cone. For me, I'll go with what the old men suggested. They wanted the hull to open up well inside the forcing cone to provide a better gas seal. Even though today the plastic wad is universal I think the same principle applies.

Larry;
To borrow from Jim, "Well Said"
To comment on this statement "although in Burrard's case in particular, he can be misquoted on the subject if you do not read ALL of what he said." This is very true. It is in fact "Fact" that both Thomas & Bell were guilty of this, taking his "Warning Against" using the higher pressure "True 2 3/4" shells in guns built for the normal 2½" load as complete condemnation of hulls longer than the chamber. He did of course also fully cover the putting of the 2½" load in the longer hull with no undesirable effects.
It might also be mentioned that Bell did in fact fire some "Low Pressure" loads put up in 3" cases in 2½ chambers which stayed within the pressure range for the gun. He "Did Not" advise doing this purposely but checked it out just to see what would occur if it happened accidently. Note this was not a factory loaded shell as there are, as mentioned, no factory loaded low pressure 3" shells.
Personally I am not too concerned about the fired case lapping into the cone a little, but would never intentionally fire a shell in which the loaded case entered the cone (likely to occur with the 3" hull in 2½" chamber. The pressure begins to fall virtually with the first movement of the charge, so long as the crimp is not impeded in it's initial opening, pressures would seem to be not much affected.

Larry,

I have selectively quoted from your previous post to focus the point of my question.

Are ANY of those "2 1/2" inch chambers really 2,50 inches? If 2-piper's post quoting diagrams from Burrard is accurate (that is, Burrard's diagrams are accurate), perhaps NONE of those "2 1/2" inch chambers were 2,50 inches (63,5 mm) but really 2 5/8 inches (67 mm). Firing a true 70 mm hulled shotshell in a 67 mm chamber is quite a bit different than firing it in a 63,5 mm chamber.

It keeps seeming to me that talking about firing 2 3/4 inch shotshells in a perhaps (apparent, even really) non-existent chamber lenght (2 1/2 inches)is really misstating reality, thereby keeping discussions like this one in fantasy land.

Perhaps this discussion might converge IF it were widely understood that expression "2 1/2" inch chambered shotguns and shotshells really means 2 9/16 (16 gauge) or 2 5/8 (12 gauge).

I am still awaiting reportage of shotguns with true 2,50 inch chamber and factory loaded shotshells that are true 2,50 inches long.

But then, maybe 65 mm shotshells in Britian are really 63,5 mm (Eley shotshell box shown in one post) and in Russia 67 mm shotshells are really 70 mm (Geno's post).

Niklas

I have a 55 gal. drum of old AA hulls that I load to shoot in damascus Parkers with 2 5/8" chambers. The load is from IMR data and I have had it tested by Tom Armbrust @4100 - 4250 PSI in a 2 3/4" chamber. I'm very comfortable with this. I just measured a random sample of these hulls and not one was over 2 11/16" in length. I would suggest that manufacturing tolerances in case thickness, internal base height, variation in powder and primer lots might cause more pressure variation than 1/16" to 1/8" inch in case length. Forcing cone configuration would be another factor. I don't believe you can really tell what you have in the way of pressures unless you test in the individual gun in which the loads are to be fired. I also believe that if you err on the side of conservatatism, it doesn't really matter.

I didn't say that, Niklas, but it's fact that shell becomes longer after firing. Take brand new shell, messure it, reload it, fire it and messure it again.
That's why factories load heavy slugs in 67,5 mm shells for 70 mm chambers.

The chamber drawings I mentioned were from Greener, 1910 (9th Edition)
From Burrard:
Vol II page91;
"The ordinary 12-bore cartridge is ""Nominally"" (emphysis mine) 2½ inches long, although to be exact the unfired (I think he is here referring to a new unloaded case) case is 2 9/16 (65mm??) inches in length."
"The standard American case was always slightly longer than the nominal 2½ inches and was actually 2 5/8 inches in length.
Vol II, page 154;
"In 1938 I tested some of the first lot of British fully crimped paper-tubed cartridges which were issued. These, as has already been explained, were loaded in 2 9/16 inch cases. I fired a series of ten shots for pressure and obtained very even and perfectly normal results. Two months later I tested another lot which were loaded in ""2 3/4"" inch paper-tube cases. the shot charge in both lots was 1 1/16 ounce and the powder charges were similar. I fired twenty-five shots for pressure and again obtained a very even series with ""NO"" higher pressures than those given by the first lot. Since 1946 I have tested many more lots and these results have ""PROVED"" quite definitely that ""For All Practical Purposes"" any increase in pressure due to the ""LONGER"" case really does not exist ""Provided"" the correct powder and shot charges for a nominal 2½ inch cartridge are used. It is true that all American fully crimped cartridges loaded with but 1 1/8 ounce of shot develop pressures which are considerably higher than those given by the corresponding British cartridges, but this is due to the relatively higher powder charge adopted by the Americans rather than to their use of the 2 3/4 inch case."
This was all virtually settled well over a half century ago, what part do we fail to understand??
The "Load" should be suitable for the gun in question.
The "Loaded" shell should have clearance & not enter the cone.
""IF"" an exceedingly old gun with very short & abrupt cone results in tearing of the crimp, use shorter shells.
Otherwise concern yourself with pointing the gun.

Thanks 2-piper!

Now, does that Burrard feller give comparable informations about chambers of those "nominal" 2 1/2 inch chambered shotguns?

Niklas

Geno,

ALL the factory slug loads I ever tested did, indeed, stretch the cases. Chamber lenght was not a factor in this. However, shot loads did not stretch the case when fired in chamber same lenght as fired case AND with chamber pressure normal for such shotshells (have seen with rough interior cases and dry, rough and tough fiber wads).

Niklas

Since some of you are using Burrard and Gough thomas to support thei sposition, i offer the following quotes from the two gentlemen in question:

Gough Thomas:(1975) "Cartridges were hitherto denoted by the length of the unloaded case, which was never greater than the length of the chamber. Since crimp closures became the rule, they have been denoted by the minimum length of the chamber for which they are designed, as stated on the carton THEY MUST NEVER BE USED IN CHAMBERS OF ANY LESSER LENGTH".

Burrard: (1932)"If cartridges are used which are too long for the chambers the pressures generated will be excessive and will cause irregular patterns irrespective of the risk of straining or even smashing the gun.....For these reasons it is always important to use the proper length of case for a particular gun, the proper length being always stamped with the proof marks on the barrel flats"

Still, these authorities, the two proof masters and the whole of the British gun trade must be wrong since one or two of you have been using the wrong ammo and have not yet shot your guns loose. I do not find your arguments compelling.

JDW,

(JDW:)As to the statement made by vh20, I was the one that gave the statement of using a 3" shell in a 2 3/4" chambered gun as a comparison of 2 1/2" to 2 3/4". Nowhere did I state that it was low pressure, it was just an analogy of using a longer shell in a shorter chamber.

No, of course you didn't, and I didn't say that you did. I'm not sure what you mean by that, it wouldn't have made sense. My point was that it is NOT the same BECAUSE there are no 3" low pressure shells manufactured anymore (although there used to be). You didn't mention ANYTHING about pressure, and that is where my disagreement came from. We don't stick 3" shells in 2-3/4" guns because they are magnums, and unless we know the pressure, we EXPECT it to be very high (same with the 2-3/4" magnums you mentioned). I can find some 3" loads in the manuals that are close to being low enough for my comfort, but not quite. Then we expect we are going to add another 10 or 15% more pressure to that because of the mismatched length. In other words, your analogy violated the premise of the practice of shooting longer shells in shorter chambers to begin with, that being that the longer shell must produce a pressure in its designed chamber length that would be appropriate for the shorter-chambered gun. Bell's test showed that even the 3" hull, if loaded to appropriate pressure, didn't cause drastic pressure increases in the short chamber, but generally speaking, 3" hulls are never loaded to appropriate pressure by any manufacturer.

(JDW:)Also you stated that older guns were never in proof even when they left the manufacturer. Wrong, they tested their guns before leaving the factory with loads that were twice the powder and shot of the loads available at the time. (Hunter Arms Co.) They just never put any proof mark on the barrels until the 1920's on some.

I'm quite aware of that, and later on they even marked them as such. But try and sell one of these guns to the gentleman in England who brought the subject up. You won't be able to because they won't accept it (i.e.illegal). They are most assuredly NOT in-proof as to their definition, and that is what I was addressing. In-Proof means a Proof House has certified it and it has not been altered or damaged since, not just the manufacturer's assurance that it is OK (which I am personally fine with, by the way).

"The reason we don't do this is the inherent PRESSURE of the shell, even when fired in a 3" chamber, not the length"

(JDW:)Actually the pressures in a 20 ga. 2 3/4" Heavy Field Load 1 1/8oz shot is equal to the pressures in a 3" of 1 1/8 oz of shot.(Lyman's 5th Edition) 2 3/4" shells also had Magnum written on them.

Again, the premise REQUIRES that the longer hull must generate a low enough pressure in its proper chamber to be appropriate for the shorter chamber (I don't have Lyman, but I'm willing to bet lunch that neither of the two loads listed are low pressure). If you skip this requirement, then the whole thing is null and void, and the discussion meaningless, and yes, all your comments on the danger could be realized.

I certainly didn't mean to offend, but I guess what I was trying to do is explain that the example you gave violated the premise the whole practice is based on. If you HAD stated 3" LOW PRESSURE, I would have said that the only data available says "no big increase in pressure". In the end, all we have to go on is data, and gut feelings. Your gut feelings obviously tell you not to do it, and that is great. I would never encourage you to. But there is NO data that I've seen that supports it. Those in the "don't do it" camp seem to imply that it is common knowledge and only a fool would try it. My question, then, is if it is common knowledge, where did we get it from? Someone had to have proved it once, right? I would just like to see those results so I can make better decisions in the future for my own practices.

I would not stick a factory 2-3/4" shell in a 2-1/2" gun because we don't know the pressure, but we do know that it could be (and likely is due to the popularity of autoloaders) near or at SAAMI max. But careful reloading practices ensure that we CAN know the pressures of our handloads (and control them) and it is ONLY then that the option becomes available. (Plus the exception of the few boutique factory loads that have published low pressures).

I think there has to be closure on this subject, it doesn't seem to be any different from the begining.

I thought that I had said modern guns when I said about putting a 3" shell in a 2 3/4" chamber. Meaning new guns. I wasn't refering to low pressure 3" shells, again I was trying to make a point about using a new manufactured 3" shell in a new modern proofed 2 3/4" chambered gun. To me that is the same difference as what the topic is.
As someone stated earlier, more gun manufacturers are making guns now with 3" chambers because they know people are going to stick a 3" shell in a 2 3/4" chambered gun.

I must have missed the part where the gentleman was from England, I thought he was from S.C.

Also did you get a long beard this morning?