Question on Chamber Length

[Autumn Daze]

Pete,Be sure to keep in mind that chambers are tapered..698-.685. Ooops never mind!

[Labowner]

20ga. AA hulls 7/8 oz. 16.5 grs. 800x Rem 209p Rem RXP-20
7500 PSI 1200 fps.

Scott has a great 3/4 oz. load maybe he will post it.

I've loaded this down with about 15grs. 800x and you can shoot them all day.

Reloading data for the twenty stinks, open a new reloading book and there isn't one 3/4 oz load in it, but they list them for the 12ga., don't get it, there should be loads down to 5/8 oz.

[Austin W Hogan]

With respect to Mr Margiotta's question, and my post of a few days ago, his measurement may reflect chamber taper, and not chamber length.
I have attached page 17 of the current SAAMI ANSI standard. Note that the length specification for modern 12 ga cases is 2.76 - .100 inches, tolerance - .250. Remington and Winchester cases measure 2.66. This is 1/32 inch over 2 5/8, probably well within tolerances for paper and plastic. Also note the plus tolerance is zero.

I would like to call your attention to the modern chamber and forcing cone drawing below the case drawing. The modern 5 degree forcing cone makes the Parker forcing cone look like a bore obstruction by comparison. Although modern ammunition seems trivially longer, an extra 1/8 of chamber length is a great safety factor in the case of a case separation or other shell failure.

Best, Austin