Load question for light bullets compared to 180 grainers

[jh45gun]

Ok here is my question: I will be shooting loads with a 180 grain bullet ( 311407) and some other 180 grainers with 17 grains of 2400 for my 30/30 and 20 grains of the same for my 7.5x55 Swiss K31 and I suppose 18 to 20 in my 308 Encore. Now once I have the sights set for these loads using a 180 grain cast bullet like the 311407 I have I really do not want to change it. I have some cast bullets lubed and gas checked that weigh 135 grains that I want to use for plinkers. Not sure what bullet it is, gas checked 3 grease groves and pointed. I have some unique I want to use up probably close to half a bottle. You guys have a starting point for me that I could come up with a load that I would not have to adjust my sights (Peep sights and Scope) I know I will have expirement but I thought you guys could give me a starting point since I am sure you guys have done the same one time or an other.

[jhalcott]

jh45, I HAVE tried to do that BUT>>>. There are a lot of variables to contend with here. It usually doesn't work. You can get windage differences along with the expected elevation changes. Your heavy bullet MIGHT hit higher than the lighter ones do. This is a function of barrel time and muzzle flip.
You need to see where each bullet hits. Then if they are close enough, you use "Kentucky windage" to shoot the plinker load. Adjusting the sights is STILL the best way to shoot multiple loads.

[trk]

Guns vary. Suggest loading 3 rounds each 1.0 grains apart from starting to hot load. Use one target for each. You will find they will rise and fall with the charges and the groups will be larger and smaller. Plot their impact against any other load. IF you're lucky the bullets that print at the same POI will also be one of the smaller groups.