I've resisted commenting on many other threads where the infamous "velocity SD" is invoked in it's raw & ignorantly bromidic form as a means of measurement in & of itself.
I think you can count on that number RegionRat stated. However, my data shows I get about 5x, often around 4X the SD for an ES. Keep in mind when talking about ES's, we're only talking about the measurement between just two data data points in a set.
I'm reading elsewhere that 1.920" is the max allowable length for 6.5 CM brass. So basically as long as I'm under that, I don't need to worry about trimming, right? Would consistency be affected much if mixing brass of different lengths?
As long as you're checking every case for length & not taking sample measurements as 6-5 Creed has only about .005" between chamber & case dimension &, cases can & do grow at different rates.
45/90, don’t make me say “ sounds like you are hyping Hybrid cases”. Lmao.
OP wondered about reducing SD/ES, without overspending. I elucidated a simple process on the cheap which should work for any cartridge that “likes” h4350. Compatibility with Fed 210, weighing to the kernel, paying attention to sound and feel, chronoing 5 of the load that sounds/feels “right”. Blind hog finds acorn. Will it repeat ? Likely. 270 just happens to fall within that cluster. As for hyping it, bullshit. More like you are hyping your hybrid case. Not that it isn’t interesting, but hardly applies to the basic question. You are a very helpful innovative guy, so I’ll cut you some slack.
So here is some load notes on 6.5 CM in an AR 10 24" barrel, no hybrid cases which are reserved for the bolt guns.
My thoughts are . . . you shouldn't focus on distance to the lands. Focus on seating depths.
It's hellaofa lot of fun! Rather than tell you anything about the data and analysis you posted, instead I will suggest that you take a step back and test the way you hope to shoot. That means, get to the distance you strive for and see how these perform. This will teach you the value of short to medium range flat fire performance versus the speed stats and short range groups.
BBBBut. . . some people like to see what can be done with a Yugo.
If I'm interpreting your comment correctly, you're really saying not to chase the lands, correct? I get that - I don't intend to go crazy constantly adjusting seating depth once I find a good ballpark unless it's necessary to maintain accuracy with my load as my barrel wears. I know some people that pick a seating depth an toss the barrel (prematurely IMO) once their lands erode enough to make that load inaccurate rather than chasing lands. I like the idea Cortina shared in a video about finding a 6-thou sweet spot and adjusting a couple thou in once accuracy starts to degrade.
I like this idea. Next time I'll run my test at ~550 yards (as my range allows for) and evaluate. It'll definitely help "magnify" my groups so it's easier to see which ones are better. And that's really more realistic to the purpose, which is to group well during a match, so that'll build some level of confidence that the ammo is good enough for a match.
Im pretty anal with my 6.5 loads as you seem to be ,I count out every grain in my precision loads ,but I also get an,ES and SD of 5 and 2..
For those around here that don't read or are not aware of the precision Rifle Blog, there's a lot of great information published there. More than one, the subject of SD's and ES's has come up and some good information has been published there. Like recently this:
When I started "precision loading" I was curious as to what's the best I could expect to do, particularly with a somewhat limited budget where I won't have things like a high end custom gun(s) or the best reloading equipment. Looking at what the professional's do, as shown in the PRB website gives me a some idea what I might be able to achieve within the scope of my limited resources. Unfortunately it's a rabbit hole very often leading to spending more than one should.
For me, in trying to figure out just how low an SD for velocity I might reasonably expect from my reloading, it was interesting to find out that different cartridges have a different ability to produce low SD's. If I had known this early on, I probably would have chosen a different cartridge than my .308. . . as much as I love my .308.
View attachment 8533631
Initially, I was just trying to get into single digit SD's. Once I did that, wanted to see how far down in the single digits I might be able to go. It's been a challenge to get my SD's in line with what I saw the pro's doing. Surprisingly to me, it doesn't take ALL the best equipment to get there, just a few pieces of good equipment and a lot of attention to details. Like with my .308, I get between 5 - 7 SD's, probably averaging in the high 5's to low 6's. For example, a recent 80 round string of 80 had SD of 6.2 with an ES of 29. I'm happy that I'm producing better than "average hand-loads". This sport challenges me in shooting small groups as possible, AND. . . getting the lowest SD's possible.
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Essentially. . . yes, don't chase the land. I will likewise make a seating depth adjustment when I see my "precision" waning. When the throat erodes enough, I might even have to change to a different/longer bullet in order to extend barrel usage. Though that will take some load development all over again.
Hmmm??? That seems pretty cynical about reports from professionals.
My process. YMMV:
Many of the claimed "all day" performance both in terms of velocity variance and group size would allow people to turn up to short range benchrest events with 6.5cm, 260, 7-08, 308 or even magnum boltface cartridges and place in regional events. That's not actually happening anywhere.
What’s really gonna change is how well you’re able to shoot as the circular error probable (CEP) will be huge when you have significant changes in feet per second of the bullet as it travels down range.
Circular error probable - Wikipedia
en.wikipedia.org
For example, I just did some testing of some hornady 6 mm Creedmoor… And the outlier was well over 100 ft./s different from the average velocity.
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I’ve had a barrel speed up on me before after a few hundred rounds. That difference was only 75 ft./s, and at 700 yard my dope was so off that I was shooting over the target.
If my bullets were 75 ft./s off from one round to the next in either direction I would be missing the target and shooting the berm below the target or the bottom of an 800 yard target, because things were so wacky.
Typically, the two major things that affect that are charge weight being consistent, and the internal volume of your brass. This is why people go out and buy auto trickelers, and go out and buy Alpha, Peterson, Lapua, Norma, or other high-end brass.
(To be fair, you can go out and buy brass, such as Winchester, Remington, PMC, Federal, Hornady, S&B, Speer, Starline, etc., and sort the hell out of that brass by weight… thus lowering the overall SD.)
Also, part of the reason people clean the living hell out of their brass is so that they get all of the excess stuff off the brass so that when they sort it, they actually get accurate weight numbers…
If you have an SD somewhere in the 10 range, then you can shoot all day long and be pretty damn consistent hitting targets with the same point of impact through your scope. (Provided you’ve worked out your dope all the way out to your intended target)
I’ll add some pictures to this to make it more obvious.
If the number of shots in the test data isn’t reported, the data is almost meaningless.
It’s a lot easier to believe “professionals” who we see standing next to trophies with their names on them. There are some incredibly precise shooters here, but far fewer than the internet chatter suggests. Unreasonable expectations lead newer reloaders and shooters astray. Often they spend a great deal of effort trying to duplicate performance that is not actually reliably reported.
