Sorting 308 brass for accuracy?

[chas442]

I am fortunate enough to have friends that work at a LGS with an indoor range. On top of that I have been collecting brass for weapons I may some day own. Now I'm working on 308. I have been able to get my hands on a variety of 308 brass in quantities of 300+ of each. This includes military and commercial.
I have read here and in other forums to sort by head stamp. That is already done. The brass is sized/deprimed using the same die for all brass. All brass are trimmed to 2.005" with an RCBS 3-way cutter. All the brass has been weighed and grouped in 1 grain increments. Example 174.0-174.9 .
The Lake City brass ranges from the 1990s on up to 2015. I have been led to believe that military brass like Lake city should be grouped by year. Rather than doing it by year I have been grouping by weight. I plan on checking the volume of samples from all weight group cases using a fine pistol powder like H110. Basically fill to the top and transfer to another in the group and again and again. This will be done on Mil and commercial brass. I also plan on comparing volume capacity between brass groupings where the different head stamp cases have the same weight grouping.
What spread is acceptable to you in case weight when sorting. Is 1or 2 grain difference in case weight critical?
Is this something that may have been tried by one of you reloading gurus?
Is what I am doing a waste of time?
I understand that the ideal scenario is to buy bulk new brand name brass and work with that. I have the time and I have the brass to do it this way rather than spend the money I like doing things that may buck the general consensus.


Thanks for any and all input.

 

[Sunray]

"...a waste of time..." Pretty much.
"...trimmed to 2.005"..." Don't forget to chamfer and deburr.
Commercial brass has all the same external dimensions. The internal dimensions really make no difference to accuracy.
Milsurp brass is currently made for use primarily in MG's. It's a bit thicker than commercial brass. Definitely separate it from commercial, but LC years don't make much difference either. Just remove the primer crimp and reduce the load by 10% and work up.
Do not use any powder for checking the volume of samples. You have no frame of reference. Plain water is used to determine capacity.
H110 isn't pistol powder. It exists because of the .30 Carbine. It just happens to work well in magnum handgun rounds too. Absolutely no need for magnum primers when using it either. Magnum primers are about the powder, not the cartridge name.

 

[Archie]

For maximum accuracy, uniformity is a viable theory. When all components are as uniform as possible, accuracy should be enhanced.

This is talking about the ammunition only, of course. A poorly bedded rifle or rifle with loose sights (scope mounts or internal reticle) will not group well with any ammunition.

However, most weights in ammunition should be evaluated by percentage of difference and not absolute weight. Consider, a .22 Hornet case (the one I just checked) weighs 49.6 grains, dirty; one fired and not cleaned. A typical .308 Winchester case (the pile of Federal once fired in my possession) goes around 175 grains. One grain difference in the Hornet is about 2% of change. One grain difference in the .308 Win cases is just over half a percent. I took an arbitrary standard of 1 grain for the .308 cases. (Which means I have to hold the .22 Hornet cases to .25 grains.)

Sunray states "...internal dimensions really make no difference to accuracy". I do not agree. Since the external dimensions are the same - especially if fired in the same chamber - the weight of the case indicates a great amount of brass. That extra brass can only be on the inside, which alters the internal capacity of the case. Changing the internal volume of the case alters the pressure attained by the powder charge, which alters the harmonics of the barrel.

This is typically ignored in a 'standard' rifle, either a military or commercial hunting rifle. Neither are routinely bedded, free floated, or triggers tuned. So the minor variances in ammunition is trampled in the major variations in the rifle.

In line with the above, cases should be cleaned as best as possible. No point in adding in the weight of the remainders of the last firing. Also, cases should be trimmed, chamfered, primer pockets cleaned and flash holes uniformed and flash holes deburred prior to weighing.

Bullets used for maximum accuracy need to be uniform as well. Weight is crucial. The good news is most manufacturers seem to hold bullets to closer tolerance than cases. Primers are pretty much take it or leave it, but can be weighed and kept more or less uniform by manufacturer and total weight by choosing the ones conforming to the standard of the loader/shooter.

One must also decide how the loads are to be used. Hunting ammo for moderate sized targets at less than 150 yards demand much less accuracy than 100 (or 1000) yard bench rest competition. I load a number of types of ammunition for WWI infantry rifles. Frankly, hitting a human torso sized target at 300 yards or so is not a terribly demanding target. So I use the cases, primers and bullets I can get and keep the powder charge as uniform as my powder measures can do. (I doubt many lots of issue ammunition is individually weighed regarding powder charge.)

So Chas442, I think you are on the right track. Of course, the rifle makes a big difference. One can waste much time and effort on reloading and still have a mediocre rifle.

 

[dh1633pm]

I shoot a lot of 308. I have two loads. My plinking loads using mixed LC brass, 150 grain FMJ's. I keep one 50 cal can filled at all times. I have a standard power charge and primer that is used. I used this on all my non target rifles. Like the Ruger GSR and so forth. And not for hunting.

I also keep a 30 cal can filled with Match ammo. This is taken a little more seriously, but not overly so. It is more accurate than me. If I was more competition orientated I would work this better, but I do ensure its non mixed LC brass, with 168 SMK's and IMR4895.

So a lot depends on your use. Those seeking the ultimate in accuracy would separate quite a bit, while others might do something else. One thing that you can do is sell the type you don't want and use the money to buy more of the kind you really do want. I did that with 45-70 brass.

 

[redbullitt]

I sort by headstamp if i am looking for consistency. Many of the brands vary significantly on their internal dimensions, which will change pressure, which will change the loads velocity and pressure AND likely POI. I always chamfer, trim, debur etc. Annealing seems to help the most out of anything a lot of times. Uniform neck tension and avoiding work hardened necks has really improved a few of my loadings.

You can weigh if you want, but i say do it right... weigh the fired cases and then find how many grains of water they hold. If you want to be as close as possible, i would try sorting them this way, by actual internal capacity. Mind you this take a lot of time, and I dont find anything like that to be necessary for any of the shooting I or most people do. Brand sorted brass for me holds .5 moa to 610 yards (my longest shot at the moment).

 

[Laphroaig]

I think a better question is "If we assume any variation in case weight is reflected in internal volume, what tolerance of internal volume are we willing to accept?" Remember that the specific gravity of brass is 8.5, meaning that brass weighs 8.5 times more than water. The following example is from a prior post (30-06 case. .308 will be not be the same but should reflect similar values), and uses +/- 1% of internal case volume as the target tolerance.

Here's some numbers from a single 30-06 case that I weighed empty, then full:

Dry case with primer = 199.4 grs.
Filled with tap water = 268.9 grs.
Case volume = 69.5 grains

OK, lets assume that I want to separate my brass to keep the internal volume within 1%, or in this case 0.7 grs. Making the assumption that any variations to the internal volume will be reflected in the weight of the dry case, and considering the specific gravity of brass is about 8.5, then the case tolerance weight would be:

.7 * 8.5 = 5.95 gr.

I'd say if your brass has a 10 or 12 grain spread from max to min weight, buy better brass.

 

[243winxb]

Deburr and uniform the flash holes.
https://www.thehighroad.org/index.php?threads/lc-7-62x51-brass-variation-by-year.763540/

I understand that the ideal scenario is to buy bulk new brand name brass and work with that. I have the time and I have the brass to do it this way rather than spend the money. I like doing things that may buck the general consensus.

To each their own.

 

[Ironicaintit]

I went through a phase where I was sorting them all out by stamp, then by weight within those groups. But then after a while I was pulling my hair out. Like for example, you said, sorting 174.0 - 174.9. Well, wouldn't the 174.9 be a better fit with the 175.0? On and on. Too much gray area for me to worry about, especially since I'm not that great a shot anyhow. So, I sort by headstamp, make them as close to identical in every other aspect of prep, and call it good.

However, between military 7.62 and civilian 308 brass, there is most definitely a difference in capacity. Enough that they should be segregated, and different loads built for each. I run roughly .5 a grain less powder in my 7.62 brass, to achieve the same affect as my 308s. (There are noteable differences in brands of 308 as well, but not nearly as drastic) my $.02

Lastly, I'm not sure if others do this, but I cut my water with dish soap to break the surface tension.

 

[joneb]

I like everything to be the same as possible, so when I am working up a load I am not chasing my tail with even more inconsistencies.

 

[444]

I don't think you are wasting your time if you are trying to do everything you can to get maximum accuracy. As you say, you can save yourself a lot of time and effort by buying GOOD commerical brass. But I get the fact that you have the brass and are trying to achieve great results with it. And FWIW: what I consider GOOD commerical brass isn't typically something someone would leave on the ground at the range.

In threads like this, there are always people who say it (whatever is being discussed) doesn't make enough of a difference for you to see the difference. And that is possible. My take on this is that there are few things you might do that will make a huge obvious difference, but all the little things combine to make a difference. In other words, each one makes a little difference and the little things add up to noticeable differences. Trying to remove as many variables as possible seems like good practice to me and if nothing else it gives you the confidence to know you are producing the best ammo you can. I see reloading as a hobby in itself and I enjoy trying to do everything I can to make my reloads as good as I can make them. Trimming, uniforming primer pockets, uniforming your flash holes, weight sorting..........none of them will cut your group size in half or anything; but all combined IMO will make a difference.

When I have sorted brass, the vast majority of the time, as I weigh the brass and sort it; the groups kind of define themselves. Obvious groups emerge. In the end, I usually end up with like three groups of brass: the light ones, the heavy ones, and the ones in the middle. I don't get real, super critical about keeping only the ones that are within .3 of a grain together.

 

[joneb]

Another thing to check for is variations in case wall thickness at the neck.
https://www.amazon.com/Anytime-Tool...191&sr=1-1-catcorr&keywords=tubing+micrometer

 

[hdwhit]

chas442 wrote:
I have read here and in other forums to sort by head stamp.

Uniformity of the brass casing can have a small impact on accuracy.

The first question is what are you going to be shooting and at what distance. If you're loading to punch paper at 200 yards at a range and harvest a deer from 125 yards come hunting season, you will probably never experience any impact from sorting brass. If you're part of the "five shots, one hole" crowd, then everything matters (i.e. case capacity, case wall thickness, neck thickness, etc.) and you want to sort your brass at least by headstamp.

Where I shoot, the largest open area is 225 yards and most of the shooting is done at 100 yards or less and is done not from a bench but off-hand. The variability introduced by firing off-hand swamps any effect the differences in case uniformity are going to have. Even so, I do sort my brass by headstamp. The reason is that I load on a non-compound leverage single stage press and different headstamp brass "feels" different in the press when I am resizing it and when I am seating the bullet and I want a more consistent "feel" so that I can stop and investigate is something seems different.

 

[chas442]

Thanks for all your input. Will be shooting out of a 26" Varmet barrel on Rock River LAR8. I am currently working up loads. Have had reasonable success. Shooting at a bench front rested. Current "good" load shooting 1" groups at 100 yards using SMK 175.
A little more preliminary info. If any one is interestedThe following list appears to be in the same weight "family". All fully prepped using the same sizing die at the same setting.

PMC
FC no nato stamp
Perfecta
WCC no nato or date
KFE
S+B

 

[joneb]

I processed 100 F-C 308 win. cases about 40% of the cases had varying case wall thickness measured at the neck, this defect runs the through the length of the case. Loading cases with this defect adds to runout or non-concentric loads.