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

My own (limited) knowledge is UK (gun and cartridge) based. I know personally where serious and expensive damage was caused to a fine gun by a few hundred 2 2/4" cartridges. It isn't necessarily a barrel issue, but simply the higher pressure/load/stresses the gun/action/woodwork are not suited to take. I do fully accept that many in cases all will be fine (and people who know what is involved will use suitably loaded cartridges), but as a rule its not wise to exceed the Proof House, or gunmakers design intentions.

"your CIP standards versus our Colonial SAAMI standard reflect that."

Is there any evidence that SAAMI standards sanction the use of 2 3/4 shells in 2 1/2 inch chambers? I recall pressure standards per gauge in PSI given by SAAME but no length recommendations.

CIP technical data is more extensive. The testing of cartridges follows a statistical model which arrives at a recommended AVERAGE pressure from a test run. Individual shells in the run can run substantially ABOVE the average, ie 740 bar max pressure allowed for 12 gauge non-magnum can have some shells exceeding 800 bar.

So in a box of 25 there may be some shells that produce higher pressure. Add to that the increase from a longer hull constricting the shot passage in the forcing cone and you create an UNNECESSARY RISK.

Bottom line from makers, CIP, proof houses, gunsmiths (and possibly SAAMI pending evidence), is do not fire longer shells than the chamber nominal length.

That warning concerns factory shells, not reloads. And it's a reasonable warning where factory loads are concerned, because the SAAMI service pressure limit for 2 3/4" (or 3") 12ga is 11,500 psi, while the CIP service pressure limit for a "Standard Proof" gun--and all 2 1/2" guns are standard proof--is 10,730 psi.

If you compare the fired length of 67/67.5mm hulls to 2 3/4" hulls--I used to have quite a collection--you will find that, in some cases, the 67's are as long or slightly longer than nominal 2 3/4" hulls. Reloading 2 3/4" hulls to appropriate low pressures and shooting them in guns with 2 1/2" chambers isn't a dangerous practice--other than in the case of guns with very short and sharply-tapered forcing cones, per the above reference. Those would almost all be 19th century guns. And in the case of those guns, even 67mm shells should be avoided--in spite of CIP's approval of those shells for 2 1/2" guns.

Twicebarrel, you must be trying to open another can of worms with your outdated and unsafe guns with Damascus barrels comment, or are you just in the market to buy a couple of more ? I love it when the local gun store has them on the shelf for sale and marked " unsafe to shoot- wall hanger ". The price is always lower. All I shoot are Parkers and Remingtons with Damascus barrels and I can't remember ever checking a chamber length - just shoot my 2 3/4" reloads in them [ for the past 10yrs with no problems ].

Paul I'm not opening anything and as of right now I have all the guns I can use. My comment was made to reinforce some common myths being tossed around.

Here is a problem I have found recently in Brit land concerning readymade cartridges especially if used in older 2� inch chambered 12 gauge guns. In the picture of the fired cartridges you can see that there is a length difference though on each of the boxes they were recommended for 65 mm or 2 � inch chambered guns. You can see that the blue case top is feathered by friction because it has entered the forcing cone and in doing so increased the recoil and more than likely the service pressure also. My conclusion is that some older guns have chamber lengths of exactly 2� inches while others are a little longer giving some leeway. The black case is manufactured by my preferred maker Hull Cartridge Company the other longer case by ELEY number two on my makers list.

Drew, we're very close on that recommendation, although I'd modify it just a bit. CIP standard proof service pressure (for 2 1/2" 12's) is 10,730 psi. Bell's tests do show increases of greater than 1,000 psi in a few cases, with a 2 3/4" hull being used in a short chamber vs in a 2 3/4" chamber. I'd recommend building in more of a safety cushion than the approx. 800 psi difference between CIP and SAAMI service pressures. Something more on the order of 1500-2000 psi. It's easy enough to find recipes that will keep pressure under 9,000 psi, so that even a 1,500 psi increase due to the longer hull--and that's a little more than Bell ever reported--will still keep you within CIP limits.

Roy Dunlaps book "Gunsmithing" copyrights of 1950 & 1963 show minimum chamber & maximum shell dimensions for the 2 3/4" 12ga.
The maximum shell is 2.76" long "Uncrimped". Maximum length of the loaded shell is 2.530" if roll crimped & 2.410 if fold crimped with a maximum diameter of .797" at end of shell.
Minimum chamber length is 2.6136" to a minimum cone of 5� per side with a minimum diame/ter at juncture of chamber & cone of ."798". He further gives a minimum diameter of .764" at a point in the cone 2.8079" from the breech. While he does not specifically say so I am quite certain these drawings were SAAMI Spec for the era. Note that if a max length shell were fired in a minimum chamber the fired shell would lap in to the cone by .1464" or a bit over 9/64". Note that this is a bit more than using a 2 3/4" shell in a "Nominal" 2�" chamber (Normally at least (65mm=2 9/16" long) but also note this was sanctioned for "ANY" 2 3/4" shell which met SAAMI Specs.
All of this was well established at least 65 years ago. All these Warnings continue to be Spread because it is undesirable to fire a Heavy loaded, max pressure 2 3/4" shell in a lightweight weight gun having 65mm chamber which was not designed for the heavier load. As noted the British have been loading shells sanctioned for the Nominal 2�" guns in a slightly longer hull since about the end of WWII.
When WWII ended I was 7 yrs old. I am not certain of Bell's age but I think him younger than me. I do appreciate that is work showed that the change from paper to plastic hulls & card & fiber to plastic wads did not change anything, but to give credit where it is due he did not "Discover" anything, just confirmed what was already well established. Sort of like confirming that a wheel will roll.

While Bell didn't discover anything, what he did do was deal with two statements that were still pretty much chiseled in stone, at least on this side of the Atlantic, when he did his "finding out for myself" series. One was that you should never fire a longer hull in a shorter chamber. The other was that you should not shoot smokeless powder loads in guns with Damascus barrels.

Miller, I think you've been around this BB long enough to remember the "Damascus roulette" crowd. What Bell did in DGJ--a publication read by a lot of people who frequent this BB--was to cause people who hadn't read Burrard (or Thomas, who said the essentially the same thing Burrard did about long shells in short chambers, but maybe 20-25 years later) to recognize that neither the length of the hull in and of itself nor the composition of the barrel should be the focus of concern. Rather, our focus should be on the contents of the shell and the pressure it produces and the overall condition of the barrel in determining what loads are appropriate for use in our vintage shotguns.

Until Bell came along, there were still a lot of "Well yeah, but . . . " comments from the Damascus Roulette and the only use the proper length of shell crowd: "Yeah, but now we have plastic hulls and wads, and those guys were talking about paper hulls and fiber or cork wads. So what they said doesn't really apply." Bell tells us EXACTLY what he used and gives the results of various recipes using modern components. Essentially shot holes in all the "yeah but" concerns of the naysayers. The result being that there are a lot more people reloading for vintage guns, including those with Damascus barrels, using smokeless powder, 2 3/4" plastic hulls, and plastic wads.

While he certainly didn't invent the wheel, I think I'd give him credit for giving us the ballistic equivalent of radial tires.

"the change from paper to plastic hulls & card & fiber to plastic wads did not change anything"

I patterned c. 30s Peters Victor 4s and fully recognize it is impossible to reproduce the ballistics of a now 80 year old shell. It would appear however that shot shell performance, or response to choke constriction, has changed somewhat. Previous attempts by Armbrust to pressure/speed test vintage shells were too inconsistent for interpretation, he felt related to primer rather than powder degradation. And pressure was occasionally increased related to stiffening of the case and wads. One would expect lower pressures to improve the pattern somewhat. It is also quite possible that shot today is harder with the addition of antimony.



At a pheasant range of 30 yds through a .030 choke. 1 1/8 oz. 3 1/4 dram @ 1255 fps. 116/152 = 76%



B&P MB Classic 5s at 30 yds/ .030 choke. 1 1/8 oz. 3 1/2 dram eq. @ 1330 fps. 171/191 = 89.5%



If someone is aware of a comparison of modern paper case/fibre wad shells with plastic case/wad shells please post for our edification and thank you!