Variation in case weight
- Thread starter Grizzlypeg
- Start date
Past time....
Generally you sort brass into batches with a 1% wt variation, for your brass you would be looking at 2gn increments. When I use Win brass I usually wind up with 6 -8 different batches sorted by wt.
When I use Lapua I usually get 3 batches using the same criteria.
I'm trying to sort out a minor source of inaccuracy. I'm getting decent groups, under 1/2" at 100 yards, but I'm getting some inexplicable shots (1/5 approx) that move it out to 3/4". I just noticed the case weight variance of up to 13 grains. The vast majority of my Winchester brass are 168 grains, but the odd one is way (159) under or 5 grains over (173).
Looks like I overlooked a major detail in reloading. Hard to believe when it was my own brass once fired. I'll weigh and sort from now on, and am looking into ordering some Lapua brass. I would sure like to see all five shots remaining together. Sometimes I start thinking its some voodoo.
Im shooting .300win mag, when i first got into it i would have great groups at 100y, then farther out id have some decent, some good and some horrible even when i felt i had made a clean shot. It was very frustrating.
It took me a while till i came around to weighing my brass and measuring internal volume with titegroup, at which time i found a large variation. I sorted them into +/- 1gr lots and pitched the real odballs. I kept the other lots in thier own marked containers and have been using the largest lot approx 65pcs of 247.5gr +/-1gr. What a difference.
Also note, all of these were formed to my chamber and theres even a few different brands. All internal case volumes measured were directly related to the weight of the case with exception to norma brass which weighs much less yet has a much shallower extractor
Groove. Very thin walls i assume. I know i should measure each and every formed cases volume but it seems as long as i keep normas out i can mix winchester, federal together so long as the weight matches.
It took me a while till i came around to weighing my brass and measuring internal volume with titegroup, at which time i found a large variation. I sorted them into +/- 1gr lots and pitched the real odballs. I kept the other lots in thier own marked containers and have been using the largest lot approx 65pcs of 247.5gr +/-1gr. What a difference.
Also note, all of these were formed to my chamber and theres even a few different brands. All internal case volumes measured were directly related to the weight of the case with exception to norma brass which weighs much less yet has a much shallower extractor
Groove. Very thin walls i assume. I know i should measure each and every formed cases volume but it seems as long as i keep normas out i can mix winchester, federal together so long as the weight matches.
- Location
- Vancouver Island
Interesting reading.
For fun and/or time killing, I just did a quick check of the 100 or so mixed Winchester and Federal .223 brass that I had primed and waiting to be charged and projectile-ized - the Winchester (25 pieces) had about a 4 gn spread (95.x to 99.x), roughly evenly distributed low to high, while the Federal (70 pieces) almost all weighed in at 96.3, plus or minus .2 - only a couple of outliers (95.9 and 97.0), not bad for the sample size!
Way better quality control at Federal, it would seem.
I've grouped the brass into bundles based on headstamp and weight and will see if they group tighter by doing so... maybe shave another 1/8" off, maybe not - either way it's another excuse/reason to hit the range!
For fun and/or time killing, I just did a quick check of the 100 or so mixed Winchester and Federal .223 brass that I had primed and waiting to be charged and projectile-ized - the Winchester (25 pieces) had about a 4 gn spread (95.x to 99.x), roughly evenly distributed low to high, while the Federal (70 pieces) almost all weighed in at 96.3, plus or minus .2 - only a couple of outliers (95.9 and 97.0), not bad for the sample size!
Way better quality control at Federal, it would seem.
I've grouped the brass into bundles based on headstamp and weight and will see if they group tighter by doing so... maybe shave another 1/8" off, maybe not - either way it's another excuse/reason to hit the range!
- Location
- Vancouver Island
Followup
Finally hit the range on the weekend with the sorted and grouped brass with an eye to seeing what difference the sorting made. In addition to the grouped brass, I also had a few control groups where the individual pieces were well over or under the group average (i.e. Winchester).
Net result: the best group of the day was from one of the mixed weight groups (just under .5 MOA from 100 yards). However, the wind had dropped off quite a bit by the time I shot the mixed groups (I know, I know - poor test planning...), so this may not quite be an apples and apples comparison. The majority of the groups were .6 to .7 on the day, with a couple of larger groups due to flyers.
So for now, I'm not going to be spending too much time worrying about case weights (for the time being, anyway) - shooter error is still the biggest source of inaccuracy in my setup.
Interesting reading.
I've grouped the brass into bundles based on headstamp and weight and will see if they group tighter by doing so... maybe shave another 1/8" off, maybe not - either way it's another excuse/reason to hit the range!
Finally hit the range on the weekend with the sorted and grouped brass with an eye to seeing what difference the sorting made. In addition to the grouped brass, I also had a few control groups where the individual pieces were well over or under the group average (i.e. Winchester).
Net result: the best group of the day was from one of the mixed weight groups (just under .5 MOA from 100 yards). However, the wind had dropped off quite a bit by the time I shot the mixed groups (I know, I know - poor test planning...), so this may not quite be an apples and apples comparison. The majority of the groups were .6 to .7 on the day, with a couple of larger groups due to flyers.
So for now, I'm not going to be spending too much time worrying about case weights (for the time being, anyway) - shooter error is still the biggest source of inaccuracy in my setup.
Thanks for the follow up. I have a lot of ammo loaded and ready for the range. Everything from weight sorted Winchester brass to brand new lapua in different charges. My issue is eliminating that 1/5 that ruins the group.
Set yourself up so you cant see the group forming through the scope. Even if you have to have your aiming mark 2 ft over the POI. Too many good groups are spoiled by the big grin on your face changeing the cheek pressure on your gun.
ShootingNewbie, weight sorted brass may not make a difference at 100 yards, but it does at 1000 yards.
- Location
- Vancouver Island
Maynard: I'll have to take your word for the time being, as I don't have anywhere to shoot that distance currently (lower Vancouver Island), but I do have a fiancee that likely wouldn't see eye-to-eye with me on the cost/benefit analysis of a half-day trip to go somewhere where I could shoot that far, so until circumstances change, I'm going to stick with this particular shortcut...
Forget about 1/2 day trips, start planning longer shooting trips. I am off to Barbados tomorrow, without the wife, for 12 days to shoot the West Indies Fullbore Championships. If I only left home for 1/2 day to shoot my wife might think that I was up to no good
