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montveil 01-05-2010 04:04 PM

Shotgun chamber recess??
I have a 410 shotgun and it has a "recessed" 3" chamber--What I mean is the chamber is larger than the bore. None of my other 12 ga have this feature.

What is this type of chamber called?
Why is it made that way?
How does it affect performance?

Thanks for any help

c3shooter 01-06-2010 01:58 AM

Willing to bet you that ALL your shotguns have that- but in the .410, the size makes the difference more apparent to the eye.

The diameter of the chamber is larger than the diameter of the bore. In front of the chamber is a tapered section, known as the forcing cone. When a shotshell fires, it opens OUT into the bore. The space with the forcing cone gives room for that to happen- otherwise you get one hell of a pressure spike- bad ju-ju.

Think about it for a second- shot sits in a shot cup inside the shell. Inside of the shell HAS to be smaller than outside- thickness of the shell wall on each side. The bore will be diameter that the shot cup will fit. CHAMBER has to be larger for shell to fit.

montveil 01-06-2010 02:51 PM

Got it-- is there any real differences if one fired a 2 3/4 shell in a 3 inch chamber? It would seem that the shot would have to "jump" over a gap.
Maybe I'm over thinking something that only a minor issue


masterPsmith 01-06-2010 03:02 PM

No problems using the 2 3/4" shells. Shoot all you like..


stalkingbear 01-06-2010 08:30 PM

In shotguns, it never hurts anything when you fire a shorter shell in a longer chamber. The only thing is if it's an semi-auto it may not function in the case of firing a light 2 3/4" (2 1/2" in 410) shell in a 3 1/2" chamber (3" in 410). The listed length of shotgun shells is measured AFTER firing-not before. This is what gives the shell room in the chamber to open up upon firing along with the larger chamber diameter.

montveil 01-06-2010 09:53 PM

Thanks to all for the replies

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