Weight sorted brass difference on charge wt and velocity

West Calamus

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Caliber 25-06: Hornaday brass wt. sorted to + or - .02gn. 176 gn.; versus R-P 270 range brass annealed, full length re-sized too 25-06 and trimmed, and sorted + or - .2 196 gn. I know the heavier brass has less room for the same charge compared to the lighter brass. So the question is heavier or lighter brass better for powder expansion , life of brass difference, less charge for same velocity in the heavier brass? The hornaday brass has about 9 firing on it and won't last forever so playing with the idea of using the resized 270 cases. ( don't worry I don't have a 270 so head stamp is not a problem). With such a large weight difference I thought it would be a good test to find out what the differences in brass weight equate to. Just asking for some heads up on what to expect. I know I need to fire R-P once through the camber before I can get real world comparisons. Thought's?
 

can1010

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weight sorting brass is almost useless what really matters is case capacity and then you will need to see a 2gr. difference within different lots of the same manufacture. comparing two different manufactures buy weight means nothing because each brass will need a different load work up depending on quality and hardness
I have brass here that is 3-4gr. difference in weight but only 0.3gr difference in capacity
don't get to hung up on weight just capacity and then not until you get over 1-2gr. to make a difference
 

MagnumManiac

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I’ll give you an example of WHY case weight means very little.
I have Norma, Winchester & Remington cases in 300WM. Prior to sectioning them lengthwise, I weighed them, took actual CC measurement of case capacity and also noted case wall thickness, web thickness and taper.
The Norma weighed the least, held the most alcohol, had the thinnest web and the thickest walls near the case head and tapered the most.
The Remington weighed within 5gr of the Winchester, held less alcohol, had a thinner web by .015” and thicker walls than the Winchester and less taper.
The Winchester held more alcohol than Remington, had a very thick web and thinner walls with more taper.
The difference with the Norma could be ASSUMED to have more capacity just from weight alone, being some 35gr lighter.
It did, but not as much as weight alone would indicate because it had very thick case walls which reduces capacity.
The ASSUMPTION that the Remington and Winchester cases being similar in capacity would have been very wrong if case weight alone was taken as the indicator without measuring the actual capacity.
Many use the fill with water and weigh method before/after. True, this tells you how many grains of water it holds, but not an actual volume measurement.
I use a Burrette to measure in CC’s, tells me exactly how much volume I have per case after I have prepped them, and I can assure you that some cases, even from the same lot do not have the same volume as the others. These cause flyers at 600 or beyond in my experience and case weight will NOT tell you this in every instance, as it may be a thicker wall on one side or other anomalies like eccentrically cut extractor grooves on some and not others.

Cheers.
 

West Calamus

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Thx Can1010 and MM for your insight. If I am understanding you both it is not a straight line correlation between case capacity and case weight but more of a actual volume of the case. I knew that I would have to work up new load data for the heavier cases. Sometimes the info one gets (or what I perceive) on these forums is not the whole story that is for sure.
 

MagnumManiac

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No it’s not a straight line correlation.
In regard to those cases I weighed and measured, it was noted that the extraction groove on the Rem cases was wider and
Deeper than the Win brass, this could have been the 5gr difference alone.

Cheers.
 

cdherman

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Couple comments:
-- Once brass is fired once or twice in a given gun, the outside dimensions of the cases are pretty much identical unless you are resizing full length and bumping the shoulder back to factory. Which you shouldn't be doing.... If the outside dimensions are the same, and the brass has different weights, then the inside dimension has GOT to be less for a heavier case. Period. This is a basic law of physics. X amount of brass occupies x/130 space in CC.
-- However, brass is a LOT denser than powder. Right at 130 grains/cc. H4831 is 14grains/cc So brass is right at 9x denser. So for instance, a case that is .02 grains heavier, can accommodate .002222 less H4831 in terms of volume. Meaningless. I sort cases into lots around 1 grain of each other. That amounts to a very negligible variation in internal capacity.
-- Back to you Hornady versus RP brass. 20 grains difference. That's actually quite a lot. 0.15 cc, or enough space to accommodate 2.15 grains of H4831. I would be VERY careful loading the heavy brass with the same load as the light brass.

-- Another way to look at it. A 257 Roberts has 57grains of water capacity. A 25-06 has about 65 grains H20 capacity. Filling a 257 Bob with a 25-06 load would be catastrophe, right? Well, a 25-06 case that weights 20 grains more, or 0.15 cc less internal space will have 2.25 grain less H20 capacity. It will be 28% of the way towards a 257 Roberts case capacity.

Weight of cartridges most certainly matters, but less than a lot of other things. It is VERY clear with your example why sorting by headstamp is a good idea at a minimum.

Finally, if you are interested, I have a large lot of various headstamp 25-06 brass. I think at least 40 rds of Hornady. Many more, in the 100's of RP and Winchester. I no longer own a 25-06. I am not alone. The 25-06 is declining in popularity. I and many others will sell you new 25-06 brass (much of mine is unfired) for a very reasonable price. I would pitch the 270 brass. Why lose 2.25 grains of case capacity? You are short changing you quarter bore...... Like my example shows, you have moved your 25-06 28% of the way to becoming a 257 Roberts.
 

West Calamus

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May 23, 2019
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Couple comments:
-- Once brass is fired once or twice in a given gun, the outside dimensions of the cases are pretty much identical unless you are resizing full length and bumping the shoulder back to factory. Which you shouldn't be doing.... If the outside dimensions are the same, and the brass has different weights, then the inside dimension has GOT to be less for a heavier case. Period. This is a basic law of physics. X amount of brass occupies x/130 space in CC.
-- However, brass is a LOT denser than powder. Right at 130 grains/cc. H4831 is 14grains/cc So brass is right at 9x denser. So for instance, a case that is .02 grains heavier, can accommodate .002222 less H4831 in terms of volume. Meaningless. I sort cases into lots around 1 grain of each other. That amounts to a very negligible variation in internal capacity.
-- Back to you Hornady versus RP brass. 20 grains difference. That's actually quite a lot. 0.15 cc, or enough space to accommodate 2.15 grains of H4831. I would be VERY careful loading the heavy brass with the same load as the light brass.

-- Another way to look at it. A 257 Roberts has 57grains of water capacity. A 25-06 has about 65 grains H20 capacity. Filling a 257 Bob with a 25-06 load would be catastrophe, right? Well, a 25-06 case that weights 20 grains more, or 0.15 cc less internal space will have 2.25 grain less H20 capacity. It will be 28% of the way towards a 257 Roberts case capacity.

Weight of cartridges most certainly matters, but less than a lot of other things. It is VERY clear with your example why sorting by headstamp is a good idea at a minimum.

Finally, if you are interested, I have a large lot of various headstamp 25-06 brass. I think at least 40 rds of Hornady. Many more, in the 100's of RP and Winchester. I no longer own a 25-06. I am not alone. The 25-06 is declining in popularity. I and many others will sell you new 25-06 brass (much of mine is unfired) for a very reasonable price. I would pitch the 270 brass. Why lose 2.25 grains of case capacity? You are short changing you quarter bore...... Like my example shows, you have moved your 25-06 28% of the way to becoming a 257 Roberts.
I like your well thought out reply. You bring up a lot of good points not the least of is that heavier fire-formed brass has less case capacity. Still trying to wrap my head around how different powders react to different fill capacities. Do some powders like more room to built up pressure versus some powders that respond better with higher fill such as 95 percent and above case fill? As far as 25-06 declining popularity- why wound I care? That particular caliber and rifle fills the niche of a 500 yard mule deer rifle for me. It is of course long action but can anyone really tell the difference in cycle time especially if one operates the bolt in a slam manner such as I do? Appreciate all the though-full replies.
 

cdherman

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If your 25-06 fills the bill for you, then keep it by all means. I had my 700 BDL rebarreled to 280 AI. The slow twist rate of the factory 25-06 barrels will not shoot long heavy bullets accurately. Or at least my barrel did not.

I miss the cartridge some, might build a custom 25-06 someday, with a faster twist. The 25-06 was and is kind of a compromise gun -- small enough for varmints, yotes, etc, but enough for deer too. Nowadays, I think most of us have multiple purpose built guns for the task at hand.

But if you want more brass, send me a PM and we can work something out.
 

MagnumManiac

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Funny, my 25-06 with a 1:10” twist has no problem shooting 115gr Berger’s.
If you want to shoot heavier bullets, then it’s up to YOU to use a barrel with a faster twist.
This trend, yes trend, of using extra heavy VLD bullets for hunting is a good thing, BUT it is NOT necessary for regular everyday hunting rifles.
Most guys I know, and myself, will not use a factory built rifle for this endeavour, we all BUILD our rifles, so the twist rate is part of the choice during the build.
The 25 cal has always been seen as a light deer round and the standard twist has sufficed. I don’t see it this way, but I also don’t see the need to stretch it further with anything more than a 115gr VLD, heck, I do most of my hunting with it out to 500 or so and am completely happy with the performance.

Also, heavy brass does NOT always end up with less volume, that is an ASSUMPTION that is often proven WRONG, as internal shape dictates the volume...ever dented a case and tried to fill it with the same load as a case that’s not dented? Won’t fit, will it? Same as a case with a thicker web and thick walls, or a case with a thin web and thin walls. You do not know the volume unless you MEASURE it.
I can spout off all the specific gravity numbers for brass too, but long ago I discovered it only is assumption when you weigh brass and think that if they weigh similar then they MUST have the same volume....just isn’t always so.

Cheers.
 

rammac

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SW Montana
Caliber 25-06: Hornaday brass wt. sorted to + or - .02gn. 176 gn.; versus R-P 270 range brass annealed, full length re-sized too 25-06 and trimmed, and sorted + or - .2 196 gn. I know the heavier brass has less room for the same charge compared to the lighter brass. So the question is heavier or lighter brass better for powder expansion , life of brass difference, less charge for same velocity in the heavier brass? The hornaday brass has about 9 firing on it and won't last forever so playing with the idea of using the resized 270 cases. ( don't worry I don't have a 270 so head stamp is not a problem). With such a large weight difference I thought it would be a good test to find out what the differences in brass weight equate to. Just asking for some heads up on what to expect. I know I need to fire R-P once through the camber before I can get real world comparisons. Thought's?
You are referring to far too many variables for any possibility of a valid guide other than to resort to the general basics of pressure in a closed vessel. So in general a smaller volume, with everything else being the same, will increase pressure and probably increase the burn rate of the powder. As said by others here, weight doesn't correlate perfectly with volume so actually measuring volume equivalency is the only way to ensure that the volumes will be the same. That being said, if you find a specific case that has the volume that is what you want and then you choose other cases of the same brand and lot number that are within a grain or so of weight then the odds are pretty good that all of those cases will have very similar volumes, but there is no absolute guarantee that they all will.
 

West Calamus

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May 23, 2019
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texas
Alright guys I will bite. What is the most economical way (without buying more gadgets) to measure case capacity? Can I simply fill case to the top with water or a non extruded powder taking before and after weights on a digital scale?
 

MagnumManiac

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Feb 25, 2008
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2,892
Well yes, weighing with water will tell you how much H2O the case holds against another case, but it must be understood this is only a comparison, not an actual volume measurement. Even water varies in weight!
I build engines, so I use Burrettes every weekend CC’ing cylinder head volumes prior to and after porting, so I already have the instrumentation to take CC measurements of my brass.
This is what I use, Lee have a list of conversions from CC’s to grains, but I forget what is at the moment.
Anyway, weighing with water will give you a benchmark to work off if that’s the only option you have.

Cheers.
 

can1010

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Feb 27, 2012
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I use water because that is what quickload uses. weigh a case, zero scale, fill with water and you have the capacity and while you do that you will notice how much case weight very compaired to capacity. I use distilled water and a barbeque injector, just be consistant on your fill level, if your level with neck or a slight bubble above neck just do it the same. you can also use alcohol which evaporates quickly and then you can begin the reloading process but if you use water make sure it is completely dry
 

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