To all at LRH.com,
The questions arises often about load development. Should I use the ladder test? Should I use the OCW method? The truth is that you can find your OCW by doing the ladder test. If you find your loads OCW by way of the ladder test and you are not satisfied with the groups youre getting, try another powder and repeat the test. The OCW (optimum charge weight) is when you have a load where loaded slightly higher and slightly lower, nail the same point of impact center to center or very close to it. This OCW may or may not yeild the best groups your rifle is capable of but affords you some lattitude when you screw up your scale a wee bit or some other factor alters your loads behavior a bit. It could also be refered to as a "node" or sweet spot of your barrel. In my opinion, there are a couple of different "nodes". There is the highest accuracy node when you find the best accuracy and there is the OCW node where even if 1 MOA is the best it will do, it is a VERY consistent 1 MOA. You can rely on it daily even if the charge weight is slightly different. Idealy, we want both together but dont always get it. Some may choose their absolute most accurate load while others choose the OCW for a more forgiving load. If youre persistent you can often find both together. Attached at the bottome of this post is a picture showing in detail how this works. It is a black and white copy of an actual test at 100 yards during my development.
You will notice 3 groups with bold arrows pointing them out. These three charge weights offer nearly identical POI's. It just so happens to be that the middle load is the most accurate charge weight. this is the OCW for this bullet and powder. The big plus sign refers to the center of group of the 46.0 load. The hollow circle refers to the center of each group of different charge weights. Notice how both .5 grain up and down from the 46.0 load is of ideal accuracy and the middle of the OCW is the better than expected. When using much larger cases, the load differences may be up to 1.0 grain.
You can find the same thing IF you are persistent and try a wide variety of powders and bullet weights. It took me trying 9 different powders and 8 different bullet types to find this "sweet spot" Of course after finding this load, I loaded 5 more and tested them in a 5 shot group. The result was a .312" 5 shot group. That is very conclusive for confirming and determining that it is a good load.
I find the powder my rifle likes best by shooting several powders with several different bullets at several different charge weights. It becomes very evident which powder it likes when you use it. Every bullet it seems can be made to shoot well and some exceptionally well. Once I nail down the powder, I try different bullets with that powder exclusively untill one shines brighter than the rest. In the case of my latest Hart 308 barrel it is the 168 AMAX and 46.0 of VV N540 seated .040" off the lands. The harmonices are unbeatable.
I hope this helps you understand when shooters refer to "harmonics" and "nodes" or "sweet spots".