.45-70 Govt. CIP Subsonic

The .45-70 Government, originally developed in the 1870s for military use, is a large, straight-walled rifle cartridge known for its powerful performance and versatility in hunting and target shooting. Its large case capacity and heavy bullet weight options also make it very well-suited to subsonic applications, especially when paired with suppressors. Due to its ability to launch bullets in excess of 400 grains at subsonic speeds (~1,050 fps or less), the .45-70 offers excellent energy retention even at lower velocities, making it ideal for short-range hunting, quiet pest control, or tactical use in suppressed firearms.

One of the key advantages of the .45-70 for subsonic loading is its bullet weight availability. Popular projectiles for subsonic loads include 405, 450, and even 500 grain cast or jacketed bullets. These projectiles maintain momentum and deliver substantial terminal performance, even without supersonic velocities. When loading subsonically, powders like IMR Trail Boss, Unique, and Vihtavuori N32C (Tin Star) are favored for their fast burn rates and ability to deliver consistent, clean ignition in large cases with low charge volumes.

Reloaders must consider powder position sensitivity, since the large case volume compared to the small powder charge can affect consistency. Some handloaders use filler materials or wad systems to improve powder burn and maintain consistent pressures. As always, care must be taken to avoid squib loads or pressure spikes from over-compression.

While most factory .45-70 rifles—especially lever-actions—are compatible with subsonic loads, barrel twist rate and chamber pressure tolerance should be considered, especially when using bullets on the heavier end. Suppressed .45-70 rifles firing subsonic loads are surprisingly quiet, with a deep, low-frequency report, making the cartridge a favorite among big-bore subsonic enthusiasts.