..... I would be more interested in these loads. I know the English had some 2" 12 Ga shells at one time but I thought they held sub 3/4 or 7/8 oz loads.
The English still do have 2" shells (bought some at MidwayUSA last year), rated at 6,000 LUP or thereabouts, but proceed carefully if you decide you like my ideas.
These shorty shells are something I'd use to get one last reload out of old hulls, as well as create these shortened specialized shotshells for my 12ga 'Survivor' singleshot. I'm hoping to create reloads that could kill grouse or cottontails to 30-35yds. Game (for camp meat not in a survival situation) would include mostly upland birds or bunnies.
I've been reloading 40+ years and some things I want to do with my 12-Survivor are
conceptual for now. But like you said 7/8oz 2" data [is available] on the Hodgdon site even if its awfully light. A 1-ounce load however is quite doable if a reloader knows how shotshell loads used to be made before one-piece plastic wads were the norm. Basically a 2" hull has plenty of volume in it (or even a 1 7/8" or 1 3/4" length 12ga hull, more about this below), for holding enough powder and wads and shot .....
In the earlier 1900's most commercial shotshells not all brass were brass and paper, and the wad [columns] usually consisted of cardboard over powder wads with felt or fiber wads stacked on those, however tall was necessary to take up whatever space wasn't needed to accommodate the amount shot used in the load. Thats similar to how I'd make my shorty loads, starting with a ballistic products (plastic) over powder wad, then with whatever (wool) felt or fiber wad. Also Mylar Wraps are available to create a "collar" to put inside the hull where the shot will reside, and when fired the wrap blows off like a wrapper. The mylar wrap isn't manditory, but back in the 1960's and 1970's Winchester made their Super-X lines of field and duck loads with "Mk-5 shot collars!" (I'd be using that same concept, to hopefully improve pattern performance by minimizing pellet deformation).
Also Ballistic Products offers a device for cutting shotshell hulls apart (to disassemble), or for shortening hulls to whatever lengths your loads might call for. The device is tricky to use, but it does cut hulls cleanly and squarely.
In addition, the Aguila Mini Shotshells (12ga) do work, with similar performance to a .410 (they have 5/8oz of shot approximately). However their wad column leaves a lot to be desired! (I cut one open to examine after shooting several). Those hulls started out at 1 3/4inches before they were sealed with a roll crimp. And a better wad would greatly improve its performance (along with an increase in pellet count!.
The biggest "key" to making shorty shells is starting with a hull with a deep, low base wad to help maximize the internal volume. Winchester AA hulls (original design) are hard to find nowadays, but Remington STS are GOOD! as well as Remington Game Club hulls along with some Federal target hulls. Actually, since these shorty are only designed (in my case) to be fired once, Federal paper hulls might make some excellent reloads once they were cut (were they chosen over plastic hulls).
To make my shorty shells I'd look at whatever load recipes were available for 1-ounce loads in my case, that use whatever powder I'm using. Then I would cut and shorten the hull and wads, fitting everything here and there untill everything fit (trial and error) but leaving the correct amount of hull for making a clean roll crimp.
Since I'd be using data under 7 or 8 thousand LUP max, they should be plenty safe!
I recall when I had a Remington M1100, that functioned most reliably with 1 1/8oz 2 3/4" trap loads, generating around 9,000-9,500 LUP! These shorty shells would probably generate pressures well below that if velocities were kept around 1100-1150-1185 feet-per-second.
Ballistic Products offers tools made specifically for making roll crimps too.
