At subsonic speeds the higher BC of the pointed bullets are only a tiny bit more streamlined than the round nose bullets. There is very little to gain with using expensive heavy match grade bullets compared to round nose bullets. I think detonation is a myth and is actually caused by double loads or firing the next round with a squib stuck in the barrel.Ĥ. It burns well even when the case is less than half full and I have never had any detonation issues. Just about any magnum pistol powder will work well. Use magnum primers, the extra heat makes the powder burn more consistently.ģ. Quiet loads made for southern Texas summers are going to be loud in an Alaskan winter.Ģ. Speed of sound temperature air formula without no barometric pressure calculator table air density of air calculation mach 1 acoustic impedance propagation air density sea level velocity ideal gas 20 degrees or 21 degrees Celsius C cold warm - sengpi At 32F it is about 1087 fps, at 90F it is about 1149 fps at -40F it is only 1004 fps. The speed of sound varies with temperature. Too slow and you run the risk of inadequate stability and excessive arc on the trajectory too fast and you go supersonic with the associated additional noise. You need to be between 10 feet per second. Get a chronograph, it is useless to develop a load without one.I can't stress this enough, if you are loading subsonic ammo without one then you wasting your time and money, period. The Vihtavuori powders (N310 and N312) are particularly interesting because they burn very quickly and cleanly and they exhibit exceptionally stable performance over an extremely wide range of environmental temperatures.ġ. Red Dot is probably the best powder to work with because it gives the highest load densities. There are other suitable powders available but these are the best to start out with. Powders suitable for subsonic loads include: N310, N312, Bullseye, Clays, Titewad, HP38 and Red Dot. I copied and pasted some of the loads and tips extracted in other threads for myself on the side, below is what i got, maybe it'll help you out too: i haven't tinkered yet, but did pick up some trailboss last week for spring / summer tinkering (if spring ever does come here in the NE). I've read in the other subsonic threads that folks are also using tightgroup, h110, and red or green dot too.
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