Yeah AtlLaw...someone is ALWAYS talking about me, at me or just plain over me...LOL...
The thumbhole allows you to get a solid, natural grip...helps absorb some of the slap...you need to open up the hole some depending on the way the stock is made so you can get your thumb through enough to get a good lock. A nice heavy hand filling shaped forend you can grip tightly is also a must have.
As far a swaging goes you can get away with a small amount DEPENDING on the construction of the bullet...Partition type or those with a heavy base section are NOT good candidates...simple cup and core can get away with quite a bit, basically you are doing the same thing the factory does.
There are a few people doing CNC bullet out of brass...you have to do a search online...Lehight Bulletts...
http://www.lehighbullets.com/index.html is one...RobGunbuilder on Accurate Reloading-Big Bore-12GaFH might...Any CNC machine shop can make them if you supply a drawing...and there are some already available bullets in the 50 cal range to get anyones juices flowing. I found a CNC shop about 50 miles away that will do a run for about $75 for the G-Code plus machine time and materials...the more in the run the less per bullet...most CNC brass bullets will run $1-3 bucks apiece out of brass so money talks and BS walks so to speak.
Anyone with autocad drawing program can design the bullet, save it to a .dwg file and that can be run on a CNC machine.
The components and loading dies are way on the pricey side so think about it from the reality side...the 500 Whisper on a trimmed down 460 Weatherby case is already on the books and was designed as a troup harrassing round, lobbing them in from 1500 yds out...and there is a 500 "something" using a trimmed WSM case that might be a bit easier to work with, both will work in the NEF with a few mods because they are low pressure, low velo rounds...the 50-140 would be an obvious excellent cartridge choice for a rechambered 500 S&W NEF, but anytime you start dealing with 700-1500 gr bullets the recoil goes up so fast most people just want to watch...and requires a specially designed and built rifle to get the weight up plus a LARGE muzzle brake...the 12GaFH uses a 3.5" shotshell or a 3.85" blown out 50 BMG case, special reamer for rechambering so from the standpoint of bigger and badder, it is a basically a .73 caliber rifle. Using bullets designed for hi BC (and high BS
) even at 1200-1500 fs the results are beyond description.
Military 50 BMG bullets have a nice high BC depending on the type from about .700 up and are usually available...the Hornady A-Max has a BC of 1.050.
As soon as I get the brake finished for my 12GA USH I will get a picture of it with the unfinished thumbhole stock. Maybe it will get someone to start breathing heavy....
...I'm also designing some hi-BC bullets to turn out on my lathe.
Lets see here... pie are square...the .458 bore area is .1647" and .73 bore area is .4185"...that means the 12GaFH is over 2 and a half times bigger in bore area... and case capacity for the 45-120 is what, 115 to 125 gr? The 12GaFH is almost 3 times that...definitly not for the faint of heart....
The 12GaFH is REALLY Ballistic Domination....LOL
Enjoy your toys...