200-220 grain bullets would be a good idea for this "concept". Place this in a 16-20" lever action carbine. (The same platfrom as Puma's Model 1892 lever gun would be perfect! It would make for a great "saddle" carbine.
Not a bad idea, eh?
A rimmed 10mm magnum already exists. In fact it predates the 10mm by quite some time: the 41 magnum.
Except, in the .410 family of bullets there are far heavier options, giving far better SD than anything made in .400. You could swage .410 bullets down for a nominal SD gain, but the difference would probably not be noted in empirical tests of terminal performance.
Since 1963, from the fertile brain of the late Elmer Keith. You are "preaching to the choir" when it comes to the .41 Remington Magnum. I wish Marlin would make another run of 1894 rifles chambered for the cartridge. 18 inches of barrel make the 210-grain hunting loads quite effective in the field. For home defense applications, the original "Police" load of 210 grain soft lead leaving a 4" barrel at 950-1000 fps worked very well. From an 18 nch barrel, you can expect 1150-1175 fps. The former will yield 616 fpe and the latter, 643 of "thump". That's enough to stop someone. ;)
Well that has been done before by none other than Randy Shelly who made the 9x25 and 9x30 Dillon'
(http://i1086.photobucket.com/albums/j441/_The_Shadow/made%209x25Dillon%20%209X30%20rimmed%2040%20caliber_zpsx4fbcdkp.jpg)
I hate to break it to you, but the Herters .401 Power Mag came out in the mid-sixty's. WAY before the Dillon.
Tony
At the risk of being branded a heretic, I gotta comment that here between the 9 and 45 is both ideal and a wasteland. It's like we are the 6.8 Spc or 6.5 Grendel of the handgun world. We see that a .400 is the ideal size, but the market just doesn't get it.
The Herter's .401 Power Mag was catalogued in 1961. It was a great forerunner to the .41 Remington Magnum. at "full-tilt" loading it was the equivalent of today's 10mm Magnum with a rimmed cartridge case. If such a cartridge were reintroduced with enough fanfare and promotion, It would find it's proper place in the Ruger Super Redhawk and a Marlin 1894 lever-action rifle.
The old .401 Power Mag had power that (believe it or not) could exceed that of the .44 Remington Magnum! Such a Revolver/Lever Action cartrdige could have a "Special" length. (10mm Auto's .992 case length). Imagine what could be done with such a rifle, or 7.5" barreled revolver in the field.
The possibilities are impressive.
Here is a great article on the 401 powermag:
http://www.gunblast.com/Fryxell_Herters401.htm
Interestingly, the author tried using 10mm auto loading dies with reasonable success. Crimping was the issue since the Herters gun needed bullets sized .403-.405.
The main thing is the bullet construction in our beloved cartridge, as you push the 10mm magnum with these bullets designed for 40 short & weak, they may not act the same at close range. But out at longer ranges and as velocity drops they will be on par with performance.
I can tell you from experience that heavy revolver cartridges benefit from a good crimp, not only for better ignition properties, but more importantly to prevent bullet jump under recoil. The inertia of recoil can act like a bullet puller. If the bullets move outward they can bind up the cylinder rotation, therefore bullets with a cannelure and a roll crimp would be in order.
Steering off the subject some, I was hoping to see a precharged air rifle chambered in 40 cal. There are some 40 cal being made but they are on the expensive side. AirForce is starting to producing 308, 357 and they are in production of the 45's as I type. SamYang makes some nice reasonably priced models in 357, 45 and 50 but no 40 cal.
Being a bullet caster and casting some various HP designs that would be useful in these type air guns. Some states are allowing the use of these big bore airguns for medium and large game hunting like deer and hogs... 8)
Someday I will get a nice big bore air rifle just be cause! ;D