Any of these with a start load velocity less than 1880 fps.
What powder do you want to use? Data from Winchester and Hodgdon websites.
http://www.winchester.com/Pages/Home.aspx
http://data.hodgdon.com/cartridge_load.asp
45-70 Government 300 gr. Super-X® JHP
Product Symbol: X4570H
Suggested Use:
Cartridge: 45-70 Government
Bullet Weight: 300
Muzzle Velocity: 1880
Ballistic Co-efficient: 0.283
300 GR. SIE HP Hodgdon Varget--- .458" 2.525" 57.0 1770 16,300 CUP--- 63.0C 2020 23,800 CUP
300 GR. SIE HP IMR IMR 4064----- .458" 2.525" 57.0 1865 22,500 CUP--- 60.5C 1992 25,100 CUP
300 GR. SIE HP IMR IMR 4895----- .458" 2.525" 57.0 1826 21,700 CUP--- 61.0C 1968 23,900 CUP
300 GR. SIE HP Hodgdon H335----- .458" 2.525" 57.0 1901 17,500 CUP--- 63.5 2143 27,400 CUP
300 GR. SIE HP Hodgdon H4895---- .458" 2.525" 58.0 1805 16,500 CUP--- 62.0C 1974 21,000 CUP
300 GR. SIE HP IMR IMR 8208 XBR- .458" 2.525" 54.0 1728 18,800 CUP--- 60.0 2023 25,400 CUP
300 GR. SIE HP IMR IMR 3031------ .458" 2.525" 56.0 1884 21,100 CUP--- 59.5C 2021 22,000 CUP
300 GR. SIE HP Hodgdon Benchmark .458" 2.525" 59.5 1907 19,400 CUP--- 63.5C 2113 27,400 CUP
300 GR. SIE HP Hodgdon H322------ .458" 2.525" 54.0 1850 18,100 CUP--- 60.0 2142 28,000 CUP
300 GR. SIE HP IMR IMR 4198------ .458" 2.525" 45.0 2008 23,500 CUP--- 48.0 2138 27,800 CUP
300 GR. SIE HP Hodgdon H4198---- .458" 2.525" 45.0 1807 16,700 CUP--- 55.0 2221 27,600 CUP
...Jimbo