A question I should know the answer to

04rubicon

04rubicon

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North of all the fuss
3" shells in a 2 3/4 champer. THe problem is the shell when fired will extend into the forcing cone correct? Is it at all possible to use 3" shells in a shotgun chambered for 2 3/4". Silly question but humor me
 
If you try this there are 3 things to consider:

1) The gun may blow up.

2) If it is a pump or autoloader it will jam as the mechanicals are designed for a shorter shell length

3) Having gotten good advice, if you do it anyway you will prove to all your friends that you are not very bright.
 
Well it can be done, but as stated you don't know what will happen. I accidentaly did this. I had borrowed a gun and didn't realize it was 2-3/4" only. As it was the identical gun to mine, I thought it was 3". Fired the first shot and the gun was jammed. Had to take the barrel off to get the shell out. When I put in back on I realized it said 2-3/4" only. Never fired another shell that day, as I was only carrying 3" shells. Made for a crappy duck hunt. But I just thanked my stars, nothing blew up.
 
There is a tapered conical section where the chamber makes the transition to the bore, called the forcing cone. The diameter of the chamber is somewhat larger than the diameter of the bore. There is concern that when a 3" shell is fired in a 2 3/4" chamber, the crimp will unfold in the forcing cone, and cannot open completely; the load will have to squeeze through. The situation with a paper shell would be worse than if a plastic shell were used, and the type of wadding would also make a difference, as would the actual measurements of the chamber, forcing cone, and bore, whether the barrel is backbored, etc.
As pointed out, it is not a wise practice.
Given the number of 2 3/4" guns, and the amount of 3" ammunition, I suspect that it is not all that rare for the longer shells to be fired in shorter chambers. Too many guns and too many shells out there for it not to happen from time to time.
How many documented cases are there of guns being burst?
 
Not a silly question. Lots of people aren't aware of the danger. They think that because the unfired 3" shell fits into the chamber, they're good to go. Glad you brought it up.
 
My brother accidently fired a 3 inch through an ithica 37.We had to remove the barrel and pound it out with a rod.Luckily, nothing worse happened, but not a mistake either of us would ever make again!
 
Been there, done that. Browning Auto 5 of 1950's era. Disassembled ,cleared and back hunting.

I now check that my pockets are cleared of any 3 in shells before using a 2 3/4 gun.
 
The reason why this happens (all the time) is as follow;

The 12Ga exists in many length;

12/50mm APL
12/60mm

12/65mm - (12Ga X 2 1/2 in) / Max shell Lenght; 65mm (2.55") / Max chamber; 67.10mm (2.65")

12/67mm

12/70mm - (12Ga X 2 3/4 in) / Max shell Lenght; 70mm (2.75") / Max chamber; 71.90mm (2.83")

12/73mm

12/76mm - (12Ga X 3 in) / Max shell Lenght; 76mm (3.00") / Max chamber; 78.20mm (3.08")

12/89mm - (12Ga X 3 1/2 in) / Max shell Lenght; 89mm (3.50") / Max chamber; 90.90mm (3.58")

Now, let's take the 4 most common ones and measure the closed shell (unfired) (from my own reserve);

The 12 X 2 1/2" measures 54mm (2.125")

The 12 X 2 3/4" measures 58.5mm (2.300") - It will easily enter a 12 X 2 1/2" chamber

The 12 X 3.0" measures 65.4mm (2.575") - It will easily enter a 12 X 2 1/2" and a 12 X 2 3/4" chamber

and the 12 X 3.5" measures 77mm (3.03") - It will easily fit a 12 X 2 3/4" and will also close in a 12 X 3.0" chamber

So, positive identification of a shotgun chambering is really important, even if most of them will stand at least one shot of the size higher... Do not make it on purpose...
 
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Baribal, great post and very informative. But I'd like to add a few comments.

Based on the proof marks on my collection of Auto-5's made in Europe and proofed with measurements in mm., but for sale in the US so they are marked for US shell sizes...

Other guns may be different but in Belgium:

65mm chambers are 2 9/16" in length and made for the 2 9/16" shell that has since dwindled in popularity and most short shells are made 2 1/2" long.

70mm chambers are 2 3/4" in length and made for the standard 2 3/4" shell

75mm chambers are 3" in length and were made for the standard 3" shell

Though 76 mm would have been closer to 3" than 75mm, that is the size they made them. Who knows why?
 
Jeff,

The mm caliber names and dimensions are from CIP, not mine. From the 2007 Edtion of the CIP from the TABLES OF DIMENSIONS OF CARTRIDGES AND CHAMBERS - TDCC

I gave the maximum shell and chamber diemensions (less the forcing cone) as per thier specs. Belgium is a CIP member, and CIP is based in Brussells.
 
I'm embarassed to admit it, but I shot a 3" shell in a Win 1200 with 2 3/4" chambers once. My brother had given me the gun and for some reason I thought it was a 3" chamber. A beaver had invaded my dugout and was making a mess of the water and trees around it. I took the gun and a couple of 3" shells and shot it in the head as it swam by. It kicked HARD but no other damage and ejected okay. I suppose I'm lucky I didn't look like the beaver. That was my second mistake that day, someone told me a beaver would float if the lungs were not perforated but it sunk like a rock. It must have floated to the surface about a week later because my lab dragged to the house and freaked out my wife. If there is a next time I think it will be on shore, with a varmit rifle.
 
Baribal,

Who can explain the difference? Not me! I wonder if they have agreed upojn a standard in more recent years.

In the meantime I have a big pile of 65 mm and 75 mm proofed guns with the factory literature specifying they were made for use with 2 9/16" and 3" shells respectivly.

Still lots to learn and fun to be had...

Jeff
 
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