Handirifle and cheatermk3 are both on the right track. Not a lot of data exists using 1680 in the 444 except with 200-220 grain bullets. Accurate Arms lists a full charge of 1680, 57 grians under a 200 grain XTP yeilding 2700 fps. Same book and Noslers 200 JPH from the 445, 40 grians of 1680 gives 1921 fps. Rifle barrel is 24", pistol barrel is 10" (Douglas Universal reciver, no gaps) Hefty difference. Accurate Arms shows 31.5 grains of 1680 driving the 300 XTP at 1595 from the 10" barrel in the 445 SM.
A gain of 300 fps from a rifle length barrel over pistol lengths is pretty normal with straight wall cases. Look at what the 357 Max Handi does over a pistol length barrel.
If we were to add 300 fps to the 445 from a rifle barrel, we'd be at 2200 fps, not too far off from where Digger says he is at. Accurate shows 35 grains of 1680 under the Hornady 265 for 1663 fps. Add 300 fps and you get 1963, once again, not too far from where Digger says he is.
Sometime back (within 2 years) Layne Simpson wrote an article about the 444. He used a load of 1680 under Hornadys 265, don't rememebr the details and can't find the magazine, but remember he was getting circa 2300 fps from the load.
For the record, I'm getting 1900 fps from 28 grains of 1680 under a 264 grain bullet in my 38-55. For what it's worth, the 445 and the 375 Winchester have nearly identical usable case capacities. Accurate shows a load of 40 grains of 1680 pushing a 200 grian bullet at 2512 fps, 38 grains pushing a 220 grian bullet at 2372. Pressures for the loads are 41,500 psi and 44,800 psi respectively. Compare that to the 444 load pushing 200 grian bullets at 2700 fps, takes 41,300 psi.
Just food for thought.
Even if the 445 will only push a 300 grainer to 1800 fps, it is still a twin of the factory 45-70 300 grain bullet load, and I assure you there is a significant reduction in recoil which will translate to more accurate shooting.
Maybe Digger will shoot some 22LR stuff over his chrony and tell us how it clocks. Thats as good a test of the equipment as can be made as most any 40 grian bullet load will do something like 1200 fps. Many keep a box or two of the same lot 22 at hand just for checking their chrony.
Edited for spelling errors, JP