H-380 in a .308 with 170 gr. bullets?

[Ignition Override]

In the fairly new Lee chart, it states with H-380 for 180 gr. bullets, use 43.0 start grains. No info for 170 grain bullets with H 380.

Is there any reason that you can't use 42 grains with lighter 170 grain bullets, for better life on brass? Only have 80 bullets in this weight.
This is just for fun plinking -to clarify- I seldom bother punching holes in paper.

The targets are mostly small chunks of concrete sprayed orange. Safety, brass life, fun with "insurgent fragments of concrete".

 

[Bart B.]

I would not use lighter charges that what was recommended to start with for 180's. Maybe use 43.5 grains to start with for that lighter bullet. To have the same peak pressure, lighter bullets need a heavier powder charge; slightly larger in this instance.

Using less that starter loads (or most loads 10% or more less than maximum) oft times causes problems. The firing pin drives .308 cases hard enough into the chamber shoulder that the shoulder's set back a few thousandths. Too little powder used won't cause enough pressure to expand the case enough to push the rear half back enough so the case head stops against the bolt face. That shortened case may be too short for safe reloading as its shoulder might not get moved back enough. If fired again with light loads after incomplete sizing, this will happen again further shorteneing the case body. If reloaded with a maximum load, case head separation will start to happen when it's fired.