A chamber question...

[JFrost]

I was looking at the long guns sales section and found this...

"New England Tracker II single shot 12 gauge, 3 inch chamber, 24 inch fully rifled barrel..."

It made me realize I don't really know what a 'chamber' is or how it works. (I know that sounds completely asinine, but there it is.)

This is a single barrel break action type of shotgun. What is it that makes it chambered for 3"? Is the chamber-to-barrel transition 'necked down' so that a 3.5" shell won't fit? What if you fire a 2" shell, will the shot 'catch' on edge of chamber? Does the rifling go all the way into the chamber? With a brass round the brass expands to 'fit' the chamber and keep all the pressure down the barrel, is this true of shotguns as well? (The small section of brass at the bottom; I can't find any pictures of shotgun shells without the brass.)Thanks

 

[Icarry2]

It relates to the the length of the shot shell the gun is made for as a maximum.

In other words it will accept both 2-3/4" shot shells and 3" shot shells.

If it were only a 2-3/4" chamber you would not be able to use 3" shot shells in the gun.

Bigger usually means more power/shot coming out..

 

[JFrost]

Found it.
Turns out there's a forcing cone on shot guns. Longer shells won't fit at all and the rifling 'tapers out' inside the cone. Still haven't found anything concerning the brass expanding or not.

 

[snorko]

In a rifle or shotgun, the chamber is that portion of the barrel into which the round to be fired is loaded or "chambered". The dimensions of the chamber are determined by the caliber or gauge of the firearm.

Some firearms are capable of firing various sizes of ammunition due to their chamber shape. Note: only shoot what the gun is marked for, typically on the barrel. For instance, a 12 gauge shotgun will most commonly have a chamber measuring 2 3/4", 3" or 3 1/2". This determines the maximum length of shell that can be fireds in a shotgun.

 

[Yeah]

Yes the brass expands. Thus the need for products like a super sizer.

Single shot shotguns marked as having 3" chambers have just that. A 3.5" shell won't physically fit into the chamber, because the chamber will not have the length to contain one. Regardless of chamber length the bore tapers down immediately after (the forcing cones you note above), then continues for a length at a fixed diameter until it reaches the choke.

2.75" shells fired in a 3" chamber do not encounter issues as the transition from chamber to forcing cone isn't a significant step down in diameter. The plastic wad, shot cup, sabot, or malleable lead are able to conform to the step to pass over it. Depending on the crimp on the shell the plastic hull may unfold to cover said step.

 

[corriedewilde]

With older shotguns with a 2.5" chamber we have a problem. A 2.75" cartridge will fit into it. The Paper/plastic casing will then fold open into the forcing cone. This will raise the pressure so much that you will damage the gun and possibly get hurt.

If this is also the case with 2.75/3" I have never checked but could very well be.

 

[JFrost]

Thanks, that answered my questions. It's sometimes surprising what you think you know.