Designing a purpose built suppressed rifle cartridge
|This whole project started with me building a 9mm suppressed bolt action bases on a Ruger M77/22 hornet. The action is short enough for a pistol round. I ended up building and incredibly quiet bolt action rifle that uses UZI magazines. The suppressor tube is a full 2" in diameter. You can hear the pop of the primer. I know people who can snap their finger and make more noise.
Anyway, that lead me to thinking about a .45 caliber gun. The problem is that rifle actions don't handle pistol length rounds well, so I started thinking about a bigger case. This lead me to try cutting off a .458 win mag to 1.5 inches. If figured if I threw a 500 gn bullet at 1000 f/s I'd really have a thumper.
Of course the problem with .458 win mag is that it's belted and required a big bolt face. So I got to thinking about using a case with a 30-06 or .308 case head. Cut off a .308 case and it's pretty close to .416. This case also fits nicely into an M-16 magazine if short enough. Since I was only going to be using a fraction of the powder charge of a .416 remington, I could afford to loose a lot of case volume. It turns out I still have excess volume which means I can expect much lower pressure on the .416 Stealth when compared to either the .223 or .308.
High rate of fire was never a prerequisite for this case. The goal was always to deliver the maximun amount of energy at 100 meters or less with as close to zero signature as practical.
I suspect the first full gun will be nothing more than a 700 short action with high scope rings and a very fat barrel. But one that can deliver 1300 Joules of energy at 100m with almost no sound.
Some special purpose subsonic ammo.
Above: .458 SP 500 gn bullet at 1050 fps
Right: .458SP, 416 Stealth and .223. The 416SP is based on a .308 case and fires a 400 gn bullet at 1000 f/s. It is the same length as the .223 andfits in an M16 magazine.