This sprang up out of another thread. In the interest of not hijacking THAT thread, I have started this new one. Quote: Originally Posted by Max Heat Lets start out by being in agreement that the closer you are to having a 100% filled case, the more efficent, in terms of velocity vs powder charge, the round becomes. From what I have found when working at (or very close to) 100% capacity, a change of say, 1% in the case-filling VOLUME of the charge makes MORE of a difference in velocity than a 1% change in the charge's WEIGHT! I have discovered that when using cases having randomly varying weights, the velocity spread will be considerably tighter if the charged is measured by dropping a marked or scribed rod into down into the case and perfectly matching the height (relative to top of the neck, so case lengths must match) level of the charge in each case, rather than by perfectly matching the weight of each charge. Does this blow your mind? But such measurements are only accurate enough when the case is filled to top of shoulder/bottom of neck minimum. This method appears to effectively negate variations in velocity caused by case weight (and thereby internal volume) differences. Now that I have gone public with my theory, for which I only have a small amount of supporting data at this time, I welcome anyone to try replicating it, and either concur (agree) or digress (disagree) that this is indeed the "case"! Quote: Originaly Posted by DocB Consider my mind blown! I can see the validity in your method. It is a very interesting technique. What do you use for a rod that's small enough not to displace the volume of the case? DocB Quote: Originally Posted by Max Heat The rounds were 7mm rem mag, and the rod was the one used to knock the case out of the sizing die and seat the primer, on a "Lee Loader" reloading kit for that round (referred to by Lee as the priming rod). The theory should apply "across the board" however, to ANY round. But the larger the diameter of the rod, without it being so tight in the neck that it's free movement might be restricted, the more accurate the volume measurement will be. It also needs to be a measurement that is "within" the neck, for maximum accuracy of the measurement. So we ARE talking no less than FULL cases, for the technique to achieve the maximun result. Filling the case is simply matter of finding exactly the right powder. Also, the finer the line is that is marked on the rod, the more accurate the measurement will be. That's why I mentioned "scribing" the rod. There IS a "variable" that could prove difficult to keep under control though. And that would be the "settling" factor, which obviously could have detrimental effects on the consistancy of the "true" volume of powder that is in the case. So absolute consistancy in the way each case is loaded & handled, will go a long way in assuring that the technique will work to it's full potential. One factor that I have given some thought to (but not tested as of yet), is how the weight of the measuring rod might affect the settling factor. The rod I was using is steel, about 5 1/2" long, and almost large enough in diameter to completely fill the ID of the case neck. I don't know if a rod that is made of a light weight material would offer more consistancy or not. It could be that the weight of the steel rod might actually HELP to equal out any case-to-case settling differences - I don't know. PS - I will admit that I did stumble upon this "discovery" purely by accident. If I hadn't been chronographing those shots, I would never have known.