Why is 3" really 2.5"?

[TDK]

I have a newb question about shotshells: Why is a shell marked 2.75" length (70mm) when the shell is actually 2.25" long? And the 3" magnum is really only 2.5"? Attached is a pic of a Winchester Super-X 2.75" Game Load with 1oz #8 shot and a Remington Slugger 3" with 7/8oz slug.

Also, a shell that is supposed to be 2.75" Super-X 1oz slug (not pictured) measures in-between these two. So I'm a little confused about what the shell length measurement is all about.

[Noobert]

I have no idea about shotgun/shells, but is this also the case with 38spl being 357?

[caoboy]

Your tape measure is inaccurate.

[TKM]

It's the length of the chamber not the unfired shell. There is extra length for the crimp to get clear of the shot or slug.

If you stuff a 3 1/2 inch shell in a 3 inch chamber (it will fit) then you will have very serious pressure problems.

And a cool new nickname like Lefty.

[RaymondMillbrae]

Shell sizes are usually taken when the hulls are opened.

When a shell is new, it is closed/crimped/rolled...hence shorter.

The importance of this measurement is in the shotguns chamber.

When the shell is shot, the hull will unfold, and it must fit the chamber in your shotgun to extract properly.

Hope that made sense.

Shoot with a purpose.

In Christ: Raymmond

[ke6guj]

Shell sizes are usually taken when the hulls are opened.

When a shell is new, it is closed/crimped/rolled...hence shorter.

The importance of this measurement is in the shotguns chamber.

When the shell is shot, the hull will unfold, and it must fit the chamber in your shotgun to extract properly.

this.

[DarkHorse]

I have no idea about shotgun/shells, but is this also the case with 38spl being 357?

[Threadjack]

.357 Magnum and .38 Special use the same caliber bullet, but the .357 case is longer. It was designed this way so people do not fire high pressure .357 rounds in guns only designed for .38 Special. If that happened, the gun would go boom.

[/Threadjack]

[bohoki]

yep its the fired length because that is the size they become in the chamber

roll crimped with a disk are longer than star crimped unfired

it does cause some confusion when it comes to tube magazine capacity

like my winchester holds 7 in the tube of 2 3/4 but roll crimped s&b buckshot also marked 2 3/4 only fit 6