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Accurate Reloading by Chronograph Pt. 3

In Blog by Rich12 Comments

Welcome back! We’re onto Part 3 of our Accurate Reloading By Chronograph series of articles here. In part one we discussed briefly the idea behind our reloading method. In part two we took our first trip to the range and reviewed the results. Now, in part three, we’re going to refine those results further! The idea is to really close in on what charge weight gets you the results you want with the bullet you chose. You want to get as close to your velocity goal as possible without running into pressure. In the end, accuracy is more important. If you have to drop a little velocity to avoid pressure or get a tighter result on the chronograph…do it! Now let’s get back into it!

Step Three: On our next trip to the range we loaded five rounds at three different charge weights. Five rounds at the charge weight producing 2996, five rounds 0.1gr lower, and five rounds 0.1gr higher. The idea was to take the results from step two and refine them. The target muzzle velocity was 3000fps so the x8.4gr load was a good place to look. It had an SD of 5fps but only across three rounds. We want to fire slightly longer strings to confirm that result. We also want to check a touch higher and a touch lower to see if the slight change does even better. Remember we’re jumping in .3gr increments here so we haven’t tested x8.3gr or x8.5gr. Those strings were fired through the same rifle using the Magnetospeed V2 chronograph with the following results:

  • x8.3gr H4350 – 2988fps SD 11fps
  • x8.4gr H4350 – 2995fps SD 3fps ES 9fps
  • x8.5gr H4350 – 2994fps SD 4fps

When we analyze the second days data we see a few interesting things. The purpose of the second day or second trip to the range is to refine the data from the first trip. The first thing we were looking for, on the first trip, was velocity and pressure data. Once we had that, it becomes time to look into refining the data into a consistent load. We picked the x8.4gr charge weight because it gave us the highest muzzle velocity, and the most consistent velocity, without signs of pressure. The numbers actually got even better with a longer string. The SD (Standard Deviation – How far off the average speed is each shot likely to be) reported by the Magnetospeed was 3fps and the ES (Extreme Spread – Maximum deviation between fastest and slowest rounds) was only 9fps! Keep in mind that single digit SD is what most guys are gunning for and we didn’t even have an ES jumping into double digits here!

Don’t Go Crazy

We shoot tactical rifle matches, not benchrest, so we tend not to obsess over the difference between 5fps and 3fps for standard deviation. Lower is always better, but if we land on a charge that yields 9fps instead of 5fps SD there won’t be any tears shed over that result. For our accurate reloading method we do load development until we produce a cartridge that gets us a single digit standard deviation and we call it a day. If you wish to further refine things on your own, that is not discouraged and we wish you well. Play with the seating depths and you can probably produce even better results. The DTACs are supposed to be pretty seating depth insensitive so we didn’t bother with a test. The beauty of this method is that it can be scaled. If you have higher accuracy requirements, you can do more testing. If you’re happy with 1/2 MOA and single digit SD…this method will get you there efficiently.

accurate reloading target

Dialed a correction after the first shot on the bottom target and all was well, top target was checking offset for another load

For the sake of this article we called it good when we saw 5fps and that decision was only reinforced when the follow up yielded 3fps. If you’re using VLDs which are known to be fussy about seating depth and jump distance, then further testing is likely a good idea.  Keep in mind the age of your barrel.  I suggest putting a minimum of 100-150 rounds through a new barrel prior to beginning load development and your accurate reloading process. The reason is because a new barrel, at least in calibers like 6.5 Creedmoor and 6×47 Lapua, will tend to pick up speed as it breaks in. It may pick up as much as 200fps, so it’s worth noting. You don’t want to do all your load development at a round count of 10 rounds only to have to redo it again at 150+ rounds because the projectiles are moving down your bore faster and thus your load is no longer properly tuned to your barrel!

Wrapping Up

So in summary: load three rounds at a time in 0.3gr increments from WELL below maximum published charge weight up to the max. Pick the fastest rounds, that are showing low standard deviation and extreme spread numbers on the chronograph. If you need to reference powder manufacturers data read our article on that subject here. If you need more information on what standard deviation and other terms mean, we recommend this article. Once you’ve picked a charge weight that gets you the velocity you want, start testing in depth. Load up 5 round strings at the charge weight you picked, as well as 0.1gr and even 0.2gr higher and lower than that charge. It just depends on how quickly the numbers tighten up and run slack again. Run the longer strings over the chronograph and pick the best one! In the next part of this series we’ll talk about how to measure the performance of your new load and see if it’s good to go, or needs further refinement! We’ll be doing a little more group shooting and some distance shooting to check performance! If you have anything to add or a question, please do so below in the comments!

Owner and Proprietor of AccuracyTech, LLC. Rich is a Firearms Enthusiast, Precision Rifle Competitor, and Writer. He is committed to bringing readers quality reviews and articles related to the Precision Shooting Sports. If you have any questions for him, please use the contact form on the site.

Comments

  1. Another good article and I’m glad I found this site!
    But (always a but right!) I have 2 questions for you.
    1) Why did you use the G1 profile vs. the G7? Doesn’t the G7 profile match the boat tail bullet profile better than the G1?
    2) I’m in the process of trying to decide which chronograph to purchase… did you find the magnetospeed affect the point of impact on your rounds or are you just using it for muzzle velocity only and then look at velocity vs POI after you decide on which charge weight is better? I’m leaning toward the Caldwell G2 or the CED M2 chronographs (mainly due to price since I can’t justify anything more expensive)

    1. Author

      I used a G1 because there isn’t a G7 or custom curve available yet. It’s a new bullet and hasn’t been tested by the Applied Ballistics crew but I’m told it’s on the list.

      The magnetospeed will move the point of impact similiar to a suppressor in my experience. It produces a repeatable POI shift and hasn’t had an effect on group size that I’ve seen.

      However, as you say, I’m already done with the chronograph when I check for accuracy so if there was an issue, it would show itself at that point.

      1. Well that explains it then! I didn’t double check my assumptions in the AP book before responding. Lesson learned.

        1. Author

          It was a good question. I will switch to G7 or CC when they make it available. The new Nosler RDF bullets should also be in the next library update along with the Hornady ELD-M offerings.

          1. I’ve picked up some 30 cal Nosler Accubond LR 210 gr and some Berger 190 gr VLD hunting rounds. Currently shoot 180 gr Accubonds out of my Wthby 30-378 and am interested in load development for it.

            But also load development in the future for my 7mm rem mag. Problem is I keep thinking of trading in several rifles and picking up the Ruger Precision Rifle… think it would be cheaper (than the 30-378 at least) to shoot and a good hunting round as well

  2. I tried your method and am getting mixed results. I am trying out that new Reloder 16 powder in the 6.5 Creedmoor in a stock Ruger Precision. Bullets are seated .019 off the lands. There is little to no data online, so I used something I found on one forum for my max and started a couple grains below that. I have been doing 4 shot groups and run 8 loads between 42.4 and 44.0g behind the 140gr ELD-M. I am using a Magnetospeed (love it). My best group size came from my highest S.D. (22) load. I know your method ignores the group size which is why I am using it. The only S.D.’s I am getting in the single digits are at 43.7 and 44.0 gr (7 & 8 respectively). But those are cruising at a full 130 fps faster than the factory Hornady rounds with the same bullet. The primers flatten out a bit, but still have a little bit of a radius around the edge. This is no worse than the lowest loads I did. But when seating the bullet, I am crunching powder for the last third of the press stroke. Is this anything to be worried about.
    BTW, I am at about 4500ft altitude at a 100 yard indoor range that is 68 degrees and the baro is about 25.79. Another question: Have you found that altitude affects burn rate and therefore speed at all? And finally, the most relevant question: Would it be wiser to settle at a 14 S.D. that is 1.5gr below my highest load, or just rock the load 0.3gr off highest with a 7 S.D. since it didn’t seem to show any worse signs than the low load? Or is there any additional steps I should take other than seating depth to try and make it better? I have heard the RPR likes .020 off the lands, and I really can’t go much longer anyway and fit in the mag. I am a little disappointed trying this method on this Ruger because I am having a hard time getting any single digit S.D.’s with this RL16 and also IMR 4451, but with my Savage LRP, almost all the loads were single digit. But it needs a new barrel (unrelated story).

    1. Author

      The extra speed isn’t worrisome because factory ammo will always be tamer than handloads. Altitude, really air density, has an effect but temperature swings are a bigger concern.

      Honestly it sounds like the burn rate of the powder is a touch slow. The crunch means it’s a compressed load. I had some of that with Reloader 17 and it jacked up my seating depth consistency. That affects your OAL and can move the bullet out and potentially raise pressure but I doubt it if you’re seating 20 off the lands.

      The SD should loosen up then tighten again so if you work your way farther down in powder charges you’re likely to see good numbers again at some point. Albeit at a lower muzzle velocity.

      I’m not there and it’s not my rifle so you have to decide what to do. I don’t think compressed loads are worth the effort. I’d look for tighter SDs at a lower charge weight or consider switching powders.

    1. Author

      Pretty soon! I have the majority of it already written but want to hold off till I do a little load development on one of my rifles. That way I can use some recent chronograph data in the article to illustrate how I go about it.

  3. Rich
    Did you ever do the follow up article (part 4) to the Accuracy Reloading by Chronograph that you mention at the end of part 3? This is where I am in the process so I would be interested to see how you moved forward.
    Gary

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