Weighing Brass/less than half case capacity fast burning charges

[1Shirt]

I have long been a proponent of weighing loaded ctgs with charges of less than half the case capacity. I have found this to be particularly expediant for charges of Unique, Red Dot, and other flake type powders due to incistancy in drop. I just 20 rounds of 7x57 with Frontier brass (that I assumed prior to loading were of the same lot---yah, know better than to assume) and found appreciable difference. Of the 20 cases, three were very lite, 8 were in the middle weight, and 9 were heavy. The lite brass was over 20 grains on average less than the heavy ones, and the 8 were in the middle. Weighing the finished loads showed me the variances, and I pulled all the blts, weighed the charges (all were the weight I wanted within a tenth of a grain, so there was no overload problem). However I needed to satisfy myself on the charge weights.

I then went back and weighed 40 more Frontier brass cases and found 21 that were within 3 gr of each other on the high side, 8 within 5 gr. on the low side, and the balance in the middle. Of the 40 there was over 25 grains difference between the heavy group and the lite weights. Now this might not be a problem with jacketed loads providing that they are not near the max level, and that accuracy would probably be minimal. However, with cast charges of fast burning powders that fill less than half of the case it could be very problematic if one did not weigh the finished load.

I have always segrated brass by manufacturer and head stamp due to lot variance. However in cases of 7x57 size cases or larger, after the segration, I have never found much more than 3-5 grain variance. That includes cases up to and including 375H&H, and military brass of the same lot. It is obvious that of the 60 cases, I probably had three different lots of brass. Just found it interesting, and will now be particularly particular about Frontier brass. Regardless, weighing finished loads of less than half case capacity charges allowed me to find the variances, and is a process I highly recommend.
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[dverna]

That procedure may not be too much of a PITA with rifle loads but it is not reasonable for pistol ammo - at least not if one does any degree of practice. Even with rifle loads, the variation in brass is more significant than the variation in powder drops. It may show a double or squib load but such an event can be prevented by seating the bullet on a rifle load immediately after the powder is dropped and NEVER letting go of the case until the bullet is in place. I cringe when someone uses a loading block to hold cases charged with powder before the bullets are seated - an accident waiting to happen.

Inconsistency of powder drops may be addressed in more efficient ways. One option is to use a powder that works better wrt powder drop consistency, or to use a powder check die on those reloading machines that can do so. I have these dies on a Dillon 650 and 1050 and they work well.

[uscra112]

I've done some brass-weighing too. More out of curiosity than anything. I'm retired from a process-control engineering profession, and I just can't give it up. A large lot of .223/5.56 range brass was the latest victim of my obsession. I did not find more than 6-8 grains variance within a brand, but between brands of .223/5.56 I've found as much as 15 grains. There is a measurable difference in internal volume when the weight difference is 5 grains. Another thing I'm finding is that the old time belief that military brass is heavier is not true, at least not when comparing US arsenal brass with US-made commercial. Recently I had a nagging feeling that I had an undercharged case after loading 200 5.56 in support of my S.i.L.'s AR-15 habit. (Found spilled powder in the loading block.) Sure enough I found it by weighing, which with a good digital scale doesn't take that long. Final check of loaded-cartridge weight is now routine. I wonder if high volume commercial loaders do this? It wouldn't be hard to automate.

[HARRYMPOPE]

I did a bunch of shooting with 9g of Unique and plainbase bullets three years ago in a P-17 30-06(6000 shots over spring and summer).I used one case and loaded on the bench with hand tools for most of the shooting.I used the chronograph for about all of the shooting expect for matches.With one case over using 10 mixed cases that varied 10-15g(if memory serve me) i saw no SD or ES changes.it my have been that the charge was so light the different volumes didn't mean as much.I hadn't expected it to be that was but it was.

[HARRYMPOPE]

"I cringe when someone uses a loading block to hold cases charged with powder before the bullets are seated - an accident waiting to happen"

I have been doing this for years with no mishaps yet.The "charge one seat a bullet" system is the one i cringe at personally.If you are careful it doesn't matter how it is done as long as you are good at your own system.

[uscra112]

I realize I'm hijacking the thread for adding this, but I'm shameless. [smilie=1:

I'm sure the benchresters have trod this ground so thoroughly that there's not a blade of grass to be seen, but I must be reading the wrong books. Brass weight variance means internal volume variance. Dropping charges vs. weighing charges has to add variance. Quickload calculations say that these variances produce pressure variance and velocity variance; as much as 5% for peak loads. How then is it the experience of so many that these variances do not add up to larger groups? What am I missing?

[HARRYMPOPE]

I realize I'm hijacking the thread for adding this, but I'm shameless. [smilie=1:

I'm sure the benchresters have trod this ground so thoroughly that there's not a blade of grass to be seen, but I must be reading the wrong books. Brass weight variance means internal volume variance. Dropping charges vs. weighing charges has to add variance. Quickload calculations say that these variances produce pressure variance and velocity variance; as much as 5% for peak loads. How then is it the experience of so many that these variances do not add up to larger groups? What am I missing?

My 30 BR(from Lapua 6BR) cases are weight sorted and i used a NECO tool to find the thick side of the case as well and it is marked.Now when the barrel was new and I was doing well it was a 1/2 MOA gun @ 100 yards.But when using plain old unsorted 7mm BR Remington cases i just could barely see a difference.I never used them to shoot matches because i was happy knowing i had the best i could use.That .5 MOA accuracy is nice fora 12# cast bullet benchrest gun but for a 6PPC is horrible and a good PPC (or 6BR)shoots in the 1's or 0's and i am sure needs all the "tricks" to get one hole groups.My buddy throws a case aside when he gets "flyer" and marks it When he shots again he can see if it was related to that particular case.My feeling is the average sporter cast bullet gun hovering around an inch to and inch and a half at 100 yards probably cant tell the difference.If i had the answer why that 4 shot 1/4" groups has one out that makes it 3/4" i would win every match i shot.

George

[1Shirt]

Devrna, agree it would be a PIA to weigh finished handgun ctgs. I am ONLY refering to rifle ctgs with loads that fill less than 1/2 the case with fast powder to eliminate the potential of double charges when loading cast boolits. Regardless of all other factors, I like the old saying: "It hurts to get hurt", and I believe that it is far better to be safe than sorry.
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