Hull Cross Sections

 There are a lot of photos cross sectioned hulls floating around, but I thought I'd throw all of mine up here for easy reference.  

As we all know, there are two main forms of hull: tapered and straight-walled.  Tapered means Winchester AA-CF, AA-HS, and Remington STS/Federal HOA.  

Straight-walled hulls are all the rest.  For the most part, they mainly differ in basewad height.  This can lead to fitment issues and differences in PSI.  Is it a big enough issue to matter?  Whatever the answer to that may be, it's at least always good to know what you're working with.

As far as I can tell, with the exception of Rio and Winchester, the various manufacturers keep the same basewad profile across all the hull lengths of a gauge.  So if you cut a Federal 12 ga 3.5" hull down to 3", it'll be just like the factory 3" version.  

Here are some 12 ga straight walled hulls.  Most are current production or just recently discontinued.  Though I did include an Activ for sake of comparison since there's a decent amount of data for Activ hulls out there.   

12 ga Fiocchi, 2.75", 3", & 3.5"

Same basewad height, but different colors.

12 ga 2.75" Cheddite or Cheddite-ish

L-R: older Fiocchi, new Fiocchi, Nobel Sport, Herter's, Challenger

Note that newer Fiocchi's are (at least for the time being) Cheddite.

Also Note that the primer pockets are not all the same diameter.  The NS is especially large.

12 ga Rio, 2.75" & 3"

L-R: new Rio, old Rio, 3" Rio

Note that the new Rio is also a Cheddite

12 ga 2.75" Federal.

L-R: paper base (FBW, Hi-Power, Old Top Gun), Gold Medal, .090" one-piece, .090" one-piece replacement, New Top Gun (NTG) 

Note that the .090" replacement is slightly deeper then the NTG.  I don't know if it was an interim design and replaced by the NTG, or if it's still around.  I've found it in steel shot loads.

Two 12 ga 2.75" Federal FBW's.  Note the variation in basewad height.  I don't know if this was intentional, or if it even makes a difference.  But it is of interest at least.  

12 ga 2.75" Federal .090 one-piece (L), 12 ga 2.75" Activ.

Not the slight taper of the Activ, which lends a slightly smaller volume.

12 ga 2.75" Federal New Top Gun (L), 12 ga 2.75" Cheddite (Herter's) 

12 ga 2.75" B&P with Gordon Basewad System, 12 ga 2.75" Gold Medal, 12 ga 2.75" Fiocchi

12 ga B&P with Gordon System Basewad

Note the crushed section of the basewad. 

Bio Ammo 12 ga 2.75" (L), 12 ga 2.75" Cheddite

The Bio Ammo hull is unfired.  I have found several of these with CRACKED basewads after one firing.  I would strongly advise against their use in reloading.  Or at least, be meticulous in checking them.

12 ga 3.5", 3", & 2.75" Remington

The two on the left have .25" basewads, the other three have .20" basewads.  The .25" are an older style.  Usually, the yellow means .20", but in older hulls, I'd still check.

Close up of the Remington 12 ga .25" (L) and .20" (R)

12 ga 2.75" (L-R): Remington .20", Federal Gold Medal, Cheddite (Herter's)

Winchester 12 ga 2.75" "polyformed"

Not that all are straight walled with plastic basewads, that's about it.  Basewads can the same height, but different colors; or the can be the same color, different heights.  

Winchester 12 ga 3" 

Showing the same individualism as the 2.75" hulls...

Here's a comparison of the tallest basewad Winchester 12 ga 3" and a Cheddite.