Load development process

[alwie]

Im fairly new to reloading and would like to understand the different approaches reloaders used to develop their loads. Please share your load development process?

[grayfox]

You'll find several methods and strong advocates/critics for each method.
I use an OBT based approach I developed for myself.
Some will use a method that works for them in larger calibers (308, 30-06, mags) and port them over to the smaller-case rounds like 6Arc... well anyway you get the picture.

I had to first of all evaluate myself as a shooter.  In order for non-chrony, shoot-for-best-group on-paper styles, you have to be a consistent sub-moa shooter no matter what, type of guy.  I'm not that good.  So I adopted a style based more on the physics and engineering concepts rather than just eyeballing groups on paper -- more often that I would like, I may have a flyer or twitch in my shooting position that would ruin a group and I wouldn't objectively be able to tell the difference. So, use mechanical engineering and physics, then add in the shooter as the last piece.

1. For any ladder of rounds you shoot, keep the delta at 1% or less of case/powder capacity.  Lots of guys will use loads 0.5 grs apart, but like I said that is really for larger case calibers, not a 6Arc or grendel.  So load deltas of 0.3 or 0.2 grs over your range.
2. Keep in mind that too-small of a delta will give you readings that are not significant since MVs they yield will no doubt be within your SD of MVs for the previous load: "noise", "in the weeds".  If you're a competition shooter you already have a method, so for the rest of us, where MV std deviations will be anywhere from 8-ish to 20+, load deltas of 0.1 grains will use powder but not give you anything significant.

I will do a ladder of shots first.  This step is to discover how the bullet, primer, case, powder and barrel react -- use mfr or published data first.  Shoot over a chrony, I use a magnetospeed but the radar types will work fine also.  Never have used the older styles since I shoot on public ranges and a magnetospeed doesn't require the range to go cold for setup... plus accuracy % is much better.  The radars came after I had already bought, so no real gain for me there.
But you have to have a chronometer, no question.
Shoot 1 round at the 0.3 gr interval over a range of at least 1.5-2.0 grains, starting somewhere low in the powder range -- don't start up close to max for your start.  Load and shoot one at a time.  Write everything down.  Now take that data home and log it and graph it in Excel, vs the mfr data, to see how your setup compares to the mfr data.
I might pause at this point to say, why do this? First of all, for a given powder and caliber combo, inside of "normal" limits, the response to an increase in powder should be a linear increase in MV (in real world there will be some fuzziness but that's ok). If not, then compression, bullet jams, too much void inside the case, etc, some abnormality is happening.  So with Excel I can see what that linear response "ought" to be (I use a linear curve fit, it's an excel function in the graph so you don't have to draw it yourself).

Now you know what the real-world MV response for your barrel and your combination should be.  From this you can look for a range that is close to a node (as defined in "optimal barrel time" - see Chris Long). 

For a particular obt node (this is based primarily on barrel length and MV, not powder or even the bullet!), pick a range surrounding it and shoot 4- or 5-shot groups at 0.2 intervals.  Again chrony and look for the best SD and tightest MV average.  Not worried about actual group size (remember I'm less than a perfect shooter anyway!). That's your target load/MV for that combo.

Now for that target load, shoot again 4- or 5-shot groups varying only the OAL, I use 0.010" intervals.  By the way, unless it's a vld I try to have my OAL end up somewhere close to 0.060-090" off the lands.  But sometimes, esp in the Arc, you don't have that capability, in that case use OALs that you can reasonably get.  Example, the Hdy 6mm 105 gr BTHP usually touches my lands at ~2.270-ish so I use 2.220. Likewise the 95 Nosler ballistic touches at 2.222, I use about 2.200.  With an AR especially I don't do any jams into lands.
This varying of OAL changes the "timing" of the bullet's exit and 1 group should have significantly better group at 100 yds than the others.  That would be the OAL you load for, at that charge, for that bullet, primer, case, powder-lot#, barrel setup.

One final note:  If you change anything, ANYTHING, in that combo, start again lower and work up.  Just like grandma's biscuit recipe, any change of ingredients can mean flat, yucky biscuits!

[Diesel Pro]

Very sound advice above. I started reloading almost 20yrs ago. I bought nice equipment and had a sky screen chrono, but limited understanding of what I was doing so I relied on grouping. I have now revisited reloading and stepped up my game a lot.

Do yourself a favor and start with a Garmin Xero chronograph. You can probably find a used Labradar cheap now since the Garmin came out, but if you have both I'd about guarantee you will only use the Garmin. I put a lot of $$$ into my Labradar and it sits as a backup I guess.

If you are not annealing DO IT! Find a friend that can do it for you or build a DIY wand type for around $200

Quickload or other ballistic software can save time and wasted shots, BUT the learning curve is a bit steep.

[alwie]

Now you know what the real-world MV response for your barrel and your combination should be.  From this you can look for a range that is close to a node (as defined in "optimal barrel time" - see Chris Long). 

For a particular obt node (this is based primarily on barrel length and MV, not powder or even the bullet!), pick a range surrounding it and shoot 4- or 5-shot groups at 0.2 intervals.  Again chrony and look for the best SD and tightest MV average.  Not worried about actual group size (remember I'm less than a perfect shooter anyway!). That's your target load/MV for that combo.

So, to estimate node time  => (barrel_len(ft) x 2) / mv ??    so, barrel = 1.5’ mv = 2560 => 

1.1718 ms   ☹️  that is beyond 7th node.

[grayfox]

Not quite that easy, which is why I use a spreadsheet for each rifle/barrel. My calcs use a corrected length for a 1-way travel down the barrel. 2560 fps is actually very close to node for 18" barrel (#6.5 in my calc), within "0.79%" - I use a range bounded by +/-1% delta from "0.0" (mathematically equal to a node MV) to find an estimated range of MVs, since this is all a working estimation. A minor factor I use is cartridge length (in this case 2.260 but it can vary slightly depending on which bullet you're using), since the bullet starts its journey a bit forward of the back end of the barrel.

[alwie]

Not quite that easy, which is why I use a spreadsheet for each rifle/barrel.  My calcs use a corrected length for a 1-way travel down the barrel.  2560 fps is actually very close to node for 18" barrel (#6.5 in my calc), within "0.79%" - I use a range bounded by +/-1% delta from "0.0" (mathematically equal to a node MV) to find an estimated range of MVs, since this is all a working estimation.  A minor factor I use is cartridge length (in this case 2.260 but it can vary slightly depending on which bullet you're using), since the bullet starts its journey a bit forward of the back end of the barrel.

For Windows haters …. apparently there is a phone app called “Barrel Time” I just downloaded. Will try using that.

[grayfox]

Here is a paper that I wrote describing my adaptation of OBT and its use for a - what I call - practical reloader.  ie, a regular guy with a decent but not necessarily premium barrel, nor an ocd competitor (who already has his/her own approach to reloading). A couple of disclaimers, lots of people (probably who are good shooters themselves) like on snipershide disbelieve or otherwise think this is bunk or whooey... whose comments I read from time to time to see if any insights can add to my understanding... but in general I look to my approach and the results I get, not to someone's opinion on an admittedly complex topic.  #2. GRT (and probably QL) predicts nodes also, which don't always coincide with what I get from my spreadsheet calcs.  Grt models the powder burn rate, and thus can develop its own acceleration profile of the bullet (that model may be more or less accurate, and the actual response you get from your bottle and lot# probably differs from the Grt); I use a simplified one instead.  #3. I have a belief that for most barrels (to some degree), powder choice and pressure curve results are not as dominant as the physical characteristics of a nominal 18-26" barrel.  Ideally, maybe yes, but practically, I haven't seen that much of an issue.
Standard disclaimers like no guarantees of safe nor useable results, use at own risk, etc.

[grayfox]

I want to add a couple of observations to the phD and such discussions who maintain basically "we don't totally understand what's going on, and you guys are using too small of 'sample sets' for any of this to be real, or accurate, or perfect, or whatever..."
We do things and take advantage of things many times in life that we do not totally understand. Not having a total comprehension of something is not a prerequisite for successfully making use of it. Example: electricity (something I have some familiarity with) -- users of this commodity typically have no clue how it's generated, how transmitted to their house, etc etc but they can use it to power their oven and make (or their wife/gf/whatever) outstanding recipes for dinner.

A more technical and "magical" example is the one that some investors use known as "technical investors" who watch various rises and falls of the stock market and make money based on "technical factors" rather than supply/demand or a company's financial performance. Those guys are wizards; I have to look at a company's financials, market performance, macro economics (or bidenomics nowadays lol!) and a product's quality/innovations to decide where to invest. I can't make heads nor tails of "1000 day hi-low averages moving curve" or such mumbo jumbo. But those guys seem to do ok.

So yes, one can make a workable theory/approach without totally understanding it as a phD might want to understand. Let those guys keep on "researching" -- I am not in favor of paralysis by analysis. A good, sound plan today is better than a perfect one... well, someday.
Give me something useful to help me in my quest today, and if research finds something better tomorrow, I'll read up on that after I have returned from my day of shooting, so to speak!!

[BD1]

Im fairly new to reloading and would like to understand the different approaches reloaders used to develop their loads. Please share your load development process?

I suppose I'm the dinosaur in the group. I start by looking for a powder that will provide 100% case fill, (or as close as I can get), without going over max pressure for the projectile I want to use. Then I look at the bullet to lands using a comparator and try for .010 off the lands, or as close as I can get with the rifle/magazine involved. I'll shoot a pressure ladder starting at the bottom and going up .5 grains until a grain below max, (knowing I can stop if velocities show I'm nearing max). This provides baseline data to compare to load manual values and what QuickLoads says.  If velocities are close to what I expect, I'll finish the pressure ladder up to the max load, or until the velocity that the max load should produce.  Then I look at the SDs and the groups to see if anything stands out as better. If I find a node, I'll repeat that load, drop down 1 grain and do a ladder up past that node in .1 grain increments. I pick the best results from that and then do a COAL ladder working down .005 in OAL at a time. This method has worked for me for many years, in a dozen rifles ranging for .223 to 28 Nosler. It does use components and I'm interested in the OBT method as a way to save components, and barrel life, finding a load. Particularly in the 6ARC as this barrel and both the 105 Scenars and the 109 Bergers are not giving me a decisive node with the pressure ladder method so far.  I have 65 rounds down the tube and so far most of it shoots consistently well. If I overlay the targets, all of the impacts for for all of the loads with both bullets used over Varget stay within 2" at 200 yards, with the last 6 groups shot all being 1-1/2 with four shots under 3/4" and one flyer. Thats both the Lapua 105at 2.240 COAL, (everything shot since I started using the Wilson seating die), and all of the Berger 109 seated at 2.3. Right now my concern is why that consistent 1 flyer out of every group of 5 shots?