I need some help from the reloading gurus.

Best response of entire thread. Guess I must have flunked physics in terms of my gross misunderstanding of solid matter properties. IIRC I got an A. In college. In case you disagree this is a physics question. I got an A in chemistry and calculus too.

Listen: I think it is correct that between different brands of brass (and for that matter different lots from the same manufacturer) the weight of the brass may not correlate completely with capacity. The thin walls of a case expand totally to the confines of the chamber upon firing (assuming a full power charge of powder). If the base/web area is reasonably consistent, then the space within the case during firing will vary based on the amount of brass in the walls. This statement is a law of physics, not opinion.

I would hope and also believe that a given lot of brass from a given manufacturer will have some degree of consistency in the base region. At least they will be using the same equipment and setting the equipment to the same tolerances. I will note: I've have even Lapua brass show bimodal or trimodal weight curves, making me think that they had more than one machine producing brass and the 2 or three lines were not perfectly in tune.

I would guess that there is a lot of brass in the base. But there is a lot of brass in the walls too, since the case is a lot longer than just the base. I don't really know just how much the ratio of un-expandable brass in the base is to the rest of the case. (what I do know, is that once you start expanding the base, you are into deep dodo...)

If the variation in brass weight is in the base, then I will concede that weighing brass is less useful. I don't know the answer to that question.

Anyone?
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.
 
OP, did you reach or get near to the same precision (group size) with the fire formed Lapua brass as with your Federal brass?
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.
 
Don't mix brass, and try to use the same lot. Weight way isn't the best way. Volume weight is the real way to determine case are the same in holding powder. Lapua or Peterson brass are very close in there volume standards for there case. I again wouldn't mix cases between those two. There are others out there that make top quality brass, but haven't used them.
 
Once I start to narrow the load down I might switch to 5 shot groups but early on it's a waste of materials in my opinion. If I shoot 3 shots and they shoot a 1.5 inch group throwing two more at it isn't going to make me feel any better about it. If they shoot 1/2" I can always load and shoot some more of them. Just how I do it.
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.

When a person loads 5 groups of 3 and shoots them, any that shoot under your goal, should be reshot with more rounds until you know 20 go into your goal. Hence my 50shot excel group calculator I'm working on!


well. I'm sure many guys here have way more experience at it than I do but In The past I've had really good luck using Lapua basically right out of the box. Basically run it through a die, trim it and load it. Even Erik Cortina does it so he claims in some videos. But this particular box shot horrible that way. Yesterday I took some of the once fired and prepped it up, loaded and shot it and it shot MUCH MUCH better. So I don't know where to put the blame but I see what I need to do I believe. I have some more loaded up to test tonight. We'll see how those do
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.
 
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.

When a person loads 5 groups of 3 and shoots them, any that shoot under your goal, should be reshot with more rounds until you know 20 go into your goal. Hence my 50shot excel group calculator I'm working on!



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%
 
Did you do any neck turning, reaming, or trimming that might be different?
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.
 
Bull Bull and more Bull you know what.

Your chamber is pretty much fixed. The case capacity after a couple firings is the chamber capacity minus the case weight, OK? Its physics. The brass has expanded to whatever size the chamber is reamed at, plus headspace. ASSUMING you are not full length resizing every round.....

Lighter cases accept more powder. Heavy cases accept less. The ratio of brass to to powder is small -- brass is denser by far, right at 20:1, but not inconsequential.

Crap, why is this concept such a challenge for some people..........
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.
 

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Sorry to disagree Herman, but brass weight is not a good indicator 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 deposited in these locations determines weight, but not 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.
 
I don't bother weight sorting brass. I will say that when there is a velocity anomaly in a group of shots, that piece of brass is usually outside the group for weight. I don't mix virgin brass with fired brass. I'll do load development on virgin brass and load what is needed. Once it is all fired then I expect to revisit the load.

I think much of the extreme fussing over brass prep is psychological more than anything. If a person has eliminated (in their mind) as many variables as possible then they have more confidence in the load. Confidence goes a long way toward shooting well. We have much better brass than when chose between Rem and Win!
 
Think I would shoot a couple groups with the Federal brass to make sure nothing changed with the rifle. That and shooting small groups keeps me motivated.
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
 
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