The big advantage of a 450 Marlin® is that it's ready to go right from the box; the ammo box that is. In order to get the full potential from a 45/70 you must handload; or, shoot the real exotic, premium stuff like Garrets®. The 450 is like the 444; everything you need is avilable in factory ammo. Just my $.02
I checked availability and pricing for the 450 and .45-70 ammo at four places – Midway, Conley Precision, Garrett and Buffalo Bore. (I could easily have gone to places like Cabelas and picked up some more .45-70 ammo, but they only list the 450 Marlin Hornady 350g FP ammo.)
The Hornady LE (LeverEvolution) ammunition for the .45-70 at 2050fps is within 50fps of the original Hornady 450 FP ammuniltion at 2100fps and delivers better downrange ballistics. And in this sample the .45-70 LE ammo was cost $5 less expensive. The new 450 LE ammunition puts the 450 somewhat ahead of the .45-70 with LE ammo but game would have a hard time telling the difference.
Once we step away from the Hornady LE ammo and performance, the advantage of the .45-70 begins to show up – a much wider range of ammo choices and availability, from inexpensive cowboy loads at $13.29 per box to Garrett 500g Exiter ammo at $180 per box.
Let’s see…
Midway offers TWENTY-ONE .45-70 loads and TWO 450 loads.
Buffalo Bore offers FIVE .45-70 loads and TWO 450 loads.
Conley Precision offers ELEVEN .45-70 loads and EIGHT 450 loads.
Garrett offers FIVE .45-70 loads and NO 450 loads.
One might also notice that the Buffalo Bore 300g Speer Uni-Cor load at 2350fps is faster than any 450 load except the Conley 250g Barnes XFN, also at 2350fps but with a lighter bullet. The Buffalo Bore load is a tad less expensive.
If you want bullets like the 300g Partition, 350g A-Frame or Speer 350g FP or 350g Woodleigh Weld-Core, or any bullet in the 460g weight or up, the .45-70 is the only choice.
450 Marlin @ Midway
$25.99 Hornady 350g LeverEvolution Elastomer Tip (Midway USA)
$28.99 Hornady 350g FP (Midway USA)
450 Marlin @ Buffalo Bore
$47.29 405 gr. JFN. (1975 fps / M.E. 3507 ft. lbs.) (Buffalo Bore)
$48.29 430 gr. LBT-LFN (1900 fps /M.E. 3446 ft. lbs. (Buffalo Bore)
450 Marlin @ Conley Precision
$28.06 450 Marlin 300 Gr. HP , 2290fps
$28.80 450 Marlin 405g JFP, 1980fps
$29.66 450 Marlin 350 Gr. Hornady Interlock , 2080fps
$37.94 450 Marlin 300 Gr. Nosler Partition , 2270fps
$43.10 450 Marlin 300g Barnes Original FP, 2250fps
$43.58 450 Marlin 400g Barnes Original FP, 1950fps
$46.45 450 Marlin 250g Barnes XFN, 2350fps
$46.45 450 Marlin 300g Barnes XFN, 2200fps
450 Marlin @ Garrett
None
.45-70 @ Midway USA
$13.29 American Ammunition 45-70 Government 405 Grain Lead Flat Nose Box of 20
$19.99 Lancer Ammunition 45-70 Government 405 Grain Lead Round Nose Flat Point Box of 20
$21.99 Ultramax Ammunition 45-70 Government 405 Grain Lead Round Nose Flat Point Box of 20
$22.99 Goex Black Dawge Blackpowder Ammunition 45-70 Government 405 Grain Lead Flat Nose Box of 20
$23.49 Hornady LEVERevolution Ammunition 45-70 Government 325 Grain Elastomer Flex Tip Box of 20
$24.99 Black Hills Cowboy Action Ammunition 45-70 Government 405 Grain Lead Round Nose Flat Point Box of 20
$24.99 Remington Express Ammunition 45-70 Government 300 Grain Semi-Jacketed Hollow Point Box of 20
$24.99 Remington Express Ammunition 45-70 Government 405 Grain Jacketed Soft Point Box of 20
$28.49 Federal Power-Shok Ammunition 45-70 Government 300 Grain Speer Hot-Cor Soft Point Box of 20
$28.99 Winchester Super-X Ammunition 45-70 Government 300 Grain Jacketed Hollow Point Box of 20
$39.99 Goex Black Dawge Pinnacle Blackpowder Ammunition 45-70 Government 405 Grain Lead Flat Nose Box of 20
$40.99 Buffalo Bore Ammunition 45-70 Government Magnum Levergun 350 Grain Jacketed Flat Nose Box of 20
$40.99 Buffalo Bore Ammunition 45-70 Government Magnum Levergun 405 Grain Jacketed Flat Nose Box of 20
$41.99 Buffalo Bore Ammunition 45-70 Government Magnum Levergun 430 Grain Lead Long Flat Nose Box of 20
$46.99 Grizzly Ammunition 45-70 Government +P 405 Grain Cast Performance Lead Wide Long Nose Gas Check Box of 20
$46.99 Grizzly Ammunition 45-70 Government +P 420 Grain Cast Performance Lead Wide Long Nose Gas Check Box of 20
$46.99 Grizzly Ammunition 45-70 Government +P 460 Grain Cast Performance Lead Wide Flat Nose Gas Check Box of 20
$48.99 Grizzly Ammunition 45-70 Government +P 350 Grain Hawk Bonded Core Jacketed Flat Point Box of 20
$48.99 Grizzly Ammunition 45-70 Government +P 350 Grain Hawk Bonded Core Jacketed Hollow Point Box of 20
$48.99 Grizzly Ammunition 45-70 Government +P 405 Grain Hawk Bonded Core Jacketed Flat Point Box of 20
$51.99 Buffalo Bore Ammunition 45-70 Government Magnum Levergun 500 Grain Full Metal Jacket Flat Nose Box of 20
.45-70 @ Conley precision
$24.99 45/70 Government (Marlin) 405 Gr. JFP , 1900fps
$27.08 45/70 Government (Marlin) 300 Gr. HP , 2100fps
$27.08 45/70 Government (Marlin) 350 Gr. Hornady Interlock , 1970fps
$34.50 45/70 Government (Marlin) 300 Gr. Nosler Partition , 2100fps
$38.87 45/70 Government (Marlin) 460 Gr. Cast Performance WFN GC , 1725fps
$38.97 45/70 Government (Marlin) 420 Gr. Cast Performance WLN GC , 1950fps
$43.54 45/70 Government (Marlin) 250 Gr. Barnes XFN , 2200fps
$43.54 45/70 Government (Marlin) 300 Gr. Barnes X FN 2100fps
$46.66 45/70 Government (Marlin) 300 Gr. Barnes Original FP , 2100fps
$46.66 45/70 Government (Marlin) 400 Gr. Barnes Original FP , 1900fps
$56.46 45/70 Government (Marlin) 400 Gr. Swift A-Frame , 1900fps
.45-70 @ Buffalo Bore
$46.19 430 gr. L.B.T.- L.F.N. - G.C. (1925 fps / M.E. 3537 ft. lbs.)
$45.14 300gr. Speer Uni Core @ 2350 fps (3678 ft. lbs.)
$45.14 405 gr. J.F.N. (2000 fps / M.E. 3597 ft. lbs.)
$45.14 350 gr. J.F.N. (2150 fps / M.E. 3592 ft. lbs.)
$56.69 500 gr. FMJFN (1625 fps /M.E. 2931 ft. lbs.)
.45-70 @ Garrett
$55.00 420-GR SUPERHARDCAST GAS-CHECKED HAMMERHEAD AT 1650-FPS
$55.00 420-GR SUPER-HARD-CAST GAS-CHECKED HAMMERHEAD AT 1850-FPS
$55.00 540-GR SUPER-HARD-CAST GAS-CHECKED HAMMERHEAD AT 1550-FPS
$65.00 350-GR WOODLEIGH WELD-CORE JSP AT 2000-FPS
$180.00 500-GRAIN SPEER TUNGSTEN SOLID AT 1530-FPS
While the situation with 450 factory ammo options and availability is slowly improving, especially with the Buffalo Bore and Conley offerings, the .45-70 retains a significant advantage in these areas.