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It should appear obvious that if two cases are the same length and one case is heavier than another case, then there is more brass in the heavier case. The brass can only be in two places in the base or the case walls. Since the outside case dimensions must conform to the dimensions of the chamber then the only other variable that the extra brass can affect is the internal volume of the case. Less internal volume gives less room for powder burn to expand. the result is a difference in velocity between the two cases (if stuffed with the exact same load and components) and or an increase or decrease in pressure. I always weigh my cases and keep them sorted by weight. This also gives me an indicator to look for possible case head separation as over time and repeated stretching and FL sizing and trimming the brass just above the base will get thinner. Differences in the alloy makeup can also account for a weight difference, but that is so small that it is barely noticeable on a normal scale. Keeping accurate notes of what you are doing is also valuable. If you don't own a chrony, buddy up with someone at the range and use theirs. My ES and ED were always very small when I used same mfg same weight (or close) cases.
I'm still working on it. I shot some 46.6 loads last night and they opened back up. So it looks like at the same seating depth 46.4 grains is the tightest it will shoot at about 5/8"-3/4". (Didn't measure). But the groups are strung vertical. So I'm definitely going to have to adjust the seating depth some which is what my next loads will be. The Federal load was set .010" off the lands so this weekend I'll load up some groups at .013" .016 .019" jump and see how those do. And then I'll update here.
I hate to say it, but your phrasing is spot on! If a 2 shot group is 2", nothing will make it 1". Pull and reuse components. If it puts 3 into 0.2", I keep shooting. It might be a 0.6" 20 shot group which will tell you if you will hit the elk, break a record, etc.
It really depends on fit to chamber OOTB. Poor fit likely won't shoot. Good fit likely will. In a factory chamber, this is a crap shoot. In a match rifle, you could make the reamer to fit the brass exactly.
100%
No. My goal for this is a 500 yard hunting rifle1/2 moa or better. I've never had to do any of that before for a 500 yard rifle. Now if my goal was 1000 yards I'd be more picky or it I have to do it to get my 1/2 moa I will. But I shouldn't need to. I believe all it needs at this point is a slight seating depth change but we'll see how that goes this weekend.
Sorry to disagree Herman, but brass weight is not a good measure of powder capacity. You do not know where the liquid brass was formed in the case. Was more brass deposited during forming in the base, in the sides, or in the neck? The amount of brass material (weight) distributed into each of these locations does not change weight, but does change capacity. If more brass is deposited in the base, the capacity is not affected, however, if more brass is deposited into a thicker wall then the capacity is affected. The only way to determine brass capacity is by filling the brass case with a liquid like water and not the weight of the brass.
Might as well just give up I have. Many here simply do not want to give up a "magic process" that actually does nothing but waste time.
Funny you say that because before I move my seating die to test some seating depths in the Lapua brass I'm going to load about 12 more in the Hornady to shoot as a control if you will to check the rifle. Great tip though. Thanks
