Reply With QuoteThe 243win Winchester brass I have has a capacity of 54.5 gr of H20 and weight from 156 to 160 gr if I remember correctly.
It's not only the capacity and weight of the brass that affect velocity but the plasticity of the alloy also matters.
Been surprised by the velocities I'm getting from my 22 inch barrel Savage 243. 44 grains H4831sc with a 95 gr sst in Winchester cases got 2915 fps. But a 100 grain Sierra Pro Hunter, same charge, in Nosler cases got 3055 fps.
My Nosler and winchester cases have been fired x5 and have been trimmed and primer pockets reamed so weighing them would be pointless at this point. Anyone out there have cases they could weigh and let me know how much they weigh? Much appreciated!
The 243win Winchester brass I have has a capacity of 54.5 gr of H20 and weight from 156 to 160 gr if I remember correctly.
It's not only the capacity and weight of the brass that affect velocity but the plasticity of the alloy also matters.
To add to Zero333's comment, squeaky clean vs fouled bores, differing bullets from jacket material to core material. Case neck tension, seating depths. There are so many variables that could be affecting velocities the list of combinations is almost endless.
The only real value added to weighing cases is so that they can be separated within that lot to have groups of cases together that are as consistent as possible. Reject the high/low or just put them together by weight for consistency.
"They couldn't hit an elephant at this distance." Last words of Gen. Sedgwik
10-4 on clean vs fouled bore! The first 3 shots had velocities all over the place. Subsequent groups settled down acceptably. The Sierra leave a lot of copper behind. Not so the Hornadys. I did read an article that reported even though there is a wide variation in case weight between brands, the author reported less than 1 1/2 grain difference in internal capacity( IIRC).
A 140 fps faster velocity with a 5 grain heavier bullet seems like a bit much.
Accurate load though <(:
You are shooting two different make bullets that vary in weight in two different brand cases. And these cases may even have different neck thickness that can effect bullet grip.
And the total difference in velocity is 140 fps and case weight does not correspond to the case internal capacity.
And if you had tested both type bullets in the in the same make case you would have found the difference the bullets made in velocity.
Right now you are mixing apples and oranges and getting fruity results.
Perhaps someone can explain to me why case weight matters. Case volume I can understand but case weight?
not to derail but I have found no correlation between case weight and cases capacity
I once took 30 .223 LC cases, weighed them dry, then weighed how many grains of water it would hold. End of the day there was no correlation between the year stamp, dry weight and volume. I still have that data if someone want to discuss it on a different thread
Heavier cases should have less internal volume assuming similar external dimensions. This is one reason reloading manuals instruct to reduce max loads when using milsurp brass. Milsurp is generally heavier than civilian due to its use in automatic weapons.
I ran out of SST's before I tried the Nosler cases so I get the apples/ oranges. It just seems odd that I got the results I did. Soon as I get more, I'll be interested to see how fast they are. I'll load up some Sierras in Winchester cases as well. Tried a 40 grain charge with the Sierras and winchester cases figuring on a velocity of 2700 fps ( Sierra data) and got an average of 2850 fps. Apparently I have a quick barrel with Sierras. Spot on with the Hornadys though. Ballistics is anything but boring!
Muddly
I buy bulk once fired Lake City 5.56 and 7.62 brass and weigh the cases just because the cases are made on different machines and will have the same headstamp date.
I weigh and sort the cases hoping they will have closer case capacity, but the only way to check case capacity is to fill each case with water and this is very time consuming.
If you go to Benchrest Central and Accurate Shooter you will find posts showing there is no correlation between case weight and volume.
Example with Lake City 7.62 cases, the old thumb rule was decrease the powder by 2.0 grains. But newer tests tell you to reduce by only 1/2 a grain and this is because the cases are made of harder brass and have more volume.
Example the first and second cases below, the Winchester WCC99 case weighs 3.5 grains more than the Lake City case. "But" there is only 0.1 grains difference in case capacity.
Below Lapua is known for quality and uniformity and the weight variations for 100 cases is only 1.2 grains. But the Winchester cases varied 6.5 grains and are not as uniform as Lapua.
Bottom line, smaller cases like the .223/5.56 are more sensitive to case capacity than larger cases like a 30-06.
Example a Lake City 5.56 case at 30.6 capacity and the Lapua case at 28.0 will cause a 6,000 psi difference in chamber pressure with the same powder charge.
So again you need to shoot the same bullet with the same powder charge in your two different type cases you have to get a better answer.
I think id start with all the same brass, then pick the ones that weight within a certain margin, then separate out the ones that shoot high or low.Originally Posted by Stumpkiller
Provided i was a good enough shooter, and had a good enough gun to start with, which requires a certain degree of honesty. lol
I personaly wouldn't be putting much faith in a chronagraph to be telling me much of anything other than ball park information.
I don't weigh mine, but I do keep them separated by manufacturer and lot number.
"They couldn't hit an elephant at this distance." Last words of Gen. Sedgwik
Considering that the average electronic scale can be off .1 grain in either direction I don't know if my measuring is all that. I used a RCBS electronic and it has a lot of creep and has to re zeroed a lot if the shop is cold. Even giving it an hour warmup time and it still creeps. I would trust my old beam scale but can't weigh cases on it
I still run an old Ohaus/RCBS 5-10 that will weigh up to 500.9 grains.
Every so often I pull out a pair of "standard" Sierra MatchKings in different calibers I keep as test/benchmark weights.
"They couldn't hit an elephant at this distance." Last words of Gen. Sedgwik
getting off topic here but as I said in a earlier post , I have see no correlation whatsoever in case weight to capacity but I was referring to the case with H20 volume. Keep in mind that was only looking at 30 LC 223 brass . I saw no correlation to year of manufacture or that any one year is more consistent than the other. That being said if the only way I would state that as a fact is if I had access to a high end lab grade scale capable of reading in milligrams such as a Sartorius that used. I would not trust ant load cell based scale no matter it's resolution, the only way to get true accuracy is using a EMFR scale
As an aside as long a beam scale that is level and with the ways and the knives clean and with the knives centered in the ways they can detect and show movement to .002 grams (a stick of Varget). I have never tried weighing a case filled with water on one, the resolution is too low. However I throw low and trickle to weight on a modified RCBS 502 when I am load testing so that I know that I am getting exactly 24.3 grains and not 24.4 or 24.2
here is a link to a page that has a lot of beam scale mods for those who would like a more more accuracy than a electronic and can't justify $1000 + on a powder scale
https://www.youtube.com/user/thetargetmaster/videos
Well i assumed the topic was accuracy, and how a case can affect that.
Obviously it does, otherwise benchresters wouldn't spend time separating them, and using the same few over and over.
For most of us, using all the same brass makes sence, and i guess everything matters when you measure group size with calipers.
But ive been to quite a few benchrest matches where some of the shooters load at the match, and watched as the powder goes from the powder measure directly into the case without weighing. Granted, the powder measures weren't part of a $200 reloading kit.
But it does raise the issue of what is and is not, high on the list of priorities as for accuracy.
Bryan Litz in his latest book observed that handloaders will do near anything that might help. I still anneal after every firing even though Litz's initial findings show it did not help or hurt. If he comes back in his next book with extended testing with the same conclusion I will probably stop
If a load is properly developed it should produce very close to the same velocity over a span of at least .3 grains and possibly more. I have a .260 Rem load that runs almost a half a grain with no more than 15FPS difference between the low and high charge. The workup was done using each test load measured to a kernel of powder using a enhanced beam scale and shot over a chronograph but once I settled on a load I now throw that charge on my RCBS Chargemaster and be confident of the rounds even if they are off by .1 or even .2 grains.
Erik Cortina was one of the first ones using this method for long range and discusses it over at Accurate Shooter http://forum.accurateshooter.com/thr...yards.3814361/
6.5 guys also discussed this method recently http://www.65guys.com/load-development-part-1-of-2/
BTW a 200+ dollar throw such as a Harrel will not throw stick powder any more accurately that a 30 dollar Lee , but it will be prettier. In fact you will get fewer kernels cut with the plastic Lee
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