I am wondering how much difference other people tollerate in their cases.

I first measure and set into different lots, select one that is closest to max or trimlength, trim to prefection then trim the others down to the same length.

After that I'll weigh them all and set them into groups once again. The largest and/or most consisatent will be my "best" lot the others above and below for plinking. anything that is over 1 grain different I will eliminate, that is for the 6PPC.

I am only this methodical with this caliber, the others stuff is pretty much for everyday close range hunting so I don't bother with too much scrutiny.

What is standard deviation that is generally tollerated here?

Hi.
So do I, if only to eliminate another factor if something goes wrong at the target end. You only have to do it once for each batch of cases anyway (bar the occasional trim to length). You can also uniform the primer pockets and ream out the flashholes as an extra measure. Whether or not you will see a difference will depend on your rifle and you. What ever cranks your handle is OK so long as its safe and gives you confidence. If your flush with cash but short on time buy Lapua or Norma brass which is pretty near perfect.

In hunting ammo I weigh and segregate to plus or minus .5g. However, I'm rethinking that. Recently I worked with some EXPENSIVE brass ($2 each!) and found a very wide disparity in weight. 20 cases were over 10g in spread. I therefore weighed their water capacity and was totally surprised. Even with that disparity the water capacity didn't vary by more than one grain! The capacity was right at 125g plus or minus .5g. I went ahead and used them and was able to shoot .3 MOA out to 300 yards. Maybe groups would be smaller with better brass, but for a heavy recoiler I was quite satisfied. I've therefore raised my tolerance a bit for hunting loads. For benchrest loads the gurus weigh to the tenth and accept NO deviation.

Bob,

That was clever checking the internal volume of the cases, as that is what's really important.

It gives one pause to think that if those cases had only about a .75 percent variation in capacity with the ten grain weight spread, might the reverse be true in some "cases."

Might some cases which weigh out very close on the scale have volume variations much greater than their similar weights would suggest?

Dan

Re:"Might some cases which weigh out very close on the scale have volume variations much greater than their similar weights would suggest?" I scraped one of those cases as there was great disparity in the water capacity but I didn't weigh the case, don't know which one it was, and the disparity was several grains, so to answer the question, yes, at least in this instance. Painful to dump a $2 piece of brass.

I don't typically check for water capacity but from that one experience it might be worth checking further and segregating based on that. My typical method of culling brass after segregating and uniforming is by shooting. I mark cases that seem to throw a flyer. Could be me, so if a marked case does it again, out it goes.

Express,
it takes 8 grain difference in brass weight to make a difference of 1 grain in powder space. If you are using loads that are over 98% of case volume it may mean that you will have to taylor your loads to the weight of the case. I usually segregate my cases into groups that are +/- 1 grain - that's .125 difference in powder space which is just slightly higher than variation from a digital scale. If you take the median case weight (the middle weight that makes up about 70 -80 % of the cases) and check the variations on those cases and segregate them into groups of +/- 1 grain. Keep the lots separate and load them accordingly.

PaulS

Bob338, I am using Sako brass, which should be pretty good, it costs me about $1.50 a shell. I am trying to find out if I can get Lapua sells too, which should be as good or better.

Do you think I can be more forgiving with these cases if only going by their wieght?

I am not throwing it out at the moment, just storing it in lots that are within .6 grain of each other. There are some real flyers that I throws away that are as much as 4 grains out but they are about 1 in 20. The rest goes into 3 categories.
Most are 119.6 to 120.3gn with smaller groups either side.

I am curious to hear what you use to plug the primer pockets with when testing for water volume capacity.
Thanks

"I am curious to hear what you use to plug the primer pockets with when testing for water volume capacity."

Express, you took the words right out of my mouth!

Bob?

Dan

Express~
Use primers to plug your brass, preferably spent ones, but live ones will do. They'll still function even though a bit damp if you don't let the water sit too long.

How I measured in the instance above is compatible with my method of preparing brass which maybe I should cover here. I fireform all my brass before final prepping and I do it using no projectile. Only thing I do with new brass is uniform the primer pockets. Then I prime, load an appropriate amount of a fast pistol powder and fill the case with corn meal, plugging the case with toilet paper. Shoot them and they are fireformed. In unbelted cases I put in a false shoulder at the neck to insure the case stays against the bolt face upon firing pin strike. At that point I trim, and in the instance above, checked water capacity with the dead primer still in place. Following that operation I deprime and finish the prepping by reaming the flash hole, and any other appropriate requirement such as neck turning, where essential. I don't turn necks normally except for tight neck chambers. Weight sorting comes in AFTER all of this.

Until the recent instance of checking water capacity on the wildcat on which I was working, I always sorted by brass weight, as mentioned above. I'm in the process of rethinking my approach. In this instance the water capacity was just an expedient way to utilize expensive brass I had to buy. I was sorting accuracy out on a customer's gun, not my own.

PaulS~
I'm curious as to your methodology for arriving at the 8g difference in brass equaling one grain of propellant. I've not done any in depth study. However, in the one instance I've studied it I came up with a different number. I've quite a few 338's. In Win Mag I was using domestic brass, most of which weigh 237g, plus or minus 3 or 4 grains usually. I discovered that by using 358 Norma Mag brass I could eliminate the initial case stretch common to belted cases which usually stretch from .015" to .024" at initial firing. The body of that brass is about .040" LONGER than the 338 Win Mag therefore allowing me to set the shoulder back at initial sizing only a thousandth or so thereby eliminating the initial stretch which leads to incipient case separation in belted cases. The Norma brass very consistently weighed 220g, even in disparate lots. That's 17g less than the domestic brass.

In firing the loads developed in the heavier domestic brass, in the lighter Norma brass it took exactly one grain of powder to attain the same velocity, everything else being identical. The load was 74g N160 behind a 225 Nosler Partition @ 2920 fps over a 35P Oehler chronograph. With the Norma brass that same velocity is achieved with 75g of N160.

I'm just wondering if the size of the cases used may have some effect which is the reason for my question to you. After all, cases can vary in head thickness and unless you can determine the capacity of the powder chamber I'm uncertain that weight difference of the case alone could be a guide as say between a 223 case and a 338 Win Mag.

Bottom line, for hunting ammo, in larger cases I agree that probably a 1g tolerance in brass weight is probably acceptable. I believe that in smaller capacity cases you might have to reduce that tolerance.