Got a bunch of 170gr bullets I normally use for .30-30 and .307Win. Can't seem to find any of my preferred 180gr RNSP bullets. And thinking of using these at a reduced rate of 2500-2600fps. What say ye?
For the .308 Win, Hodgdon's max load with a 175 gr Sierra is 45 gr Varget at 2,690 fps.
For the .30-30, Hodgdon's max load is 33 gr Varget at 2,168 fps and a starting charge of 29.5 gr at 1,976 fps.
In order to get in that window, I'd try 32 - 36 gr (Maximum) of Varget to start with in the .308 Winchester.
I'd also use mag primers for consistent ignition.
If you have a chrony, that would be a great help to figure out where you're at and adjust the load accordingly, I wouldn't launch those bullets any faster than 2,300 fps personally.
