Armory Sponsor
Posted: 12/8/2008 4:27:22 AM EDT
|
I was tallying up my brass last night and I've got a large mix. Half is LC of mixed years, and a lot of Winchester (marked both WCC and Winchester) and PMP. Some RP, PMC, FC.
How picky do I need to be when switching between manufactures and lots of the same manufacture? I'd hate to have to work up half a dozen or more different loads. Some of the LC is as old as the 70's and some is 2000. Most ammo will be for plinking and I'd only expect to stay w/in 2moa and stay a little south of max loads, probably 25.5gr of w748 w/ 55gr fmjs. (ifrc) I'd probably separate out one particular type for precession loading. |
|
I conducted an experiment to determine just what affect mixed brass had on accuracy. I conducted the experiment with 308 cartridges, so take that into consideration.
I worked up a load that was acceptably accurate in my StG 58. The load was: 168 gr Hornady Hollow Point Boat Tail Match bullet 45 gr WCC 846 surplus powder L C 64 brass (once fired trimmed to 2.00) Remington 9 1/2 Magnum primer. I used the L C 64 brass as a control group because I had 100 rds of factory loaded ammo that I had shot through my M1A and had saved the brass so I knew it's history. I had 20 cases of L C 66 MATCH brass, but I had no idea how many times it had been loaded before I aquired it. I had/have other U S milsurp brass and I used it it this experiment. I loaded up 20 rds with the LC 64 brass and the afore mentioned data. The 4 groups of 5 rounds each averaged 1.8 inches @ 100 yrds. The next batch was the LC 66 MATCH brass with the same data. The 4 groups of 5 rds averaged 1.8 inches, but the point of impact had shifted to the right 2.3 inches. (center to center) The next batch was LC 75 brass. 4 groups of 5 rds averaged 2 inches with a point of impact 1.4 inches high and .75 inches right. The next batch was a mix of LC, WRA, TW, and RA brass. The years were a mix with the oldest being 64 and the newest being 04. The 4 groups of 5 rds averaged 2.5 inches with a POI center 1.2 inches right and 1 inch high. Iron sights. Benched and bagged. Weather was fair and wind was negligible. |
|
I'm assuming you're talking about .223/5.56mm brass-you didn't actually say what caliber you're talking about in your post. Considering the relatively small size of these cases, you could simply start out by sizing and trimming everything, and then sorting them by weight. Interestingly, you'll find some wide variations in the same lot of brass, depending on the manufacturer. GI LC brass in 5.56mm can vary as much as 3+ grains in my observations, and these are all from the same lot and package.
Also, you should consider the kind of loading you'll be doing. If you're after "precision" loads that all go through the same hole in the paper at 300 yards, you should be more attentive to uniformity in every component. If you're after <1MOA ammunition that is reliable and consistent, you may be able to be a little more relaxed in component selection and measurement. I try to keep my brass separated by headstamp, but that can be pretty flexible too. For example, how much difference will there be between 5.56mm LC brass headstamped 2004 and 2006? How different is a bunch of cases with three of those fancy machinery dimples in the head versus five dimples? For my current interests, I randomly choose something like 5-10% of cases with a given manufacturer's stamp and weigh them. If they're pretty close to each other, that's great. If not, I re-sort by some condition other than headstamp, like weight, but this doesn't happen often with .223 brass. I just sort stuff like 9mm brass by headstamp for convenience in batch assembly. I have yet to find any significant difference in performance between nickled Hornady 9mm brass and 20 year old WWC GI 9mm brass, so I don't bother with separating them beyond what I do. |
|
I sort by headstamp. The reason is to achieve proper neck tension. Different brasses have different neck thicknesses which require different size collets to achieve the same neck tension.
I know some will disagree but I have not found accuracy differences if the brass is sized and trimmed properly. I qualify that statement because I only use Lapua, Hornady and some Black Hills brass. I have found dramatic accuracy differences with different brand bullets of the same weight. |
Armory Sponsor