Load Development

[choprzrul]

I did use the timer on my cell phone between shots.....2 minutes

I also use a chamber chiller fan between shots to pull some heat out of the barrel

[cbr9290318]

Since you have a chronograph you can load one round at each powder charge going up in 1% increments.

If your baseline starting load is 23 grains you would go up in 0.2 grain increments. If your starting load is 52 grains your incremental increase would be 0.5 grains



Now go to the reloading bench and load up one round using your incremental charge weight from book minimum to book maximum and maybe two to three rounds above book maximum.



You set up your chronograph and have your notebook and a pen handy and shoot your rounds evenly spaced for time without ever looking at your target. You can measure the base of the case to make sure you are not pushing the charge to hot. 0.001 casehead expansion is your limit.



Now you plot on a piece on paper your velocities in a vertical pattern going from low to high but you put the change in velocity next to the powder charge.



What you should see is a hourglass looking change in your velocities something like this.



2850 FPS

2874 FPS +24

2890 FPS +16

2905 FPS +15

2918 FPS +13

2940 FPS +22

2965 FPS +25

2983 FPS +18

3000 FPS +17

3012 FPS +12

3035 FPS +23

3078 FPS +43

3148 FPS +70



This would show you two nodes one at 2918 FPS and another at 3012 FPS plus pressure problems at 3078 and above.



An incremental powder increase would normally produce an incremental velocity increase with two exceptions.

Exception one is when your near a node the increase is less.

Exception two is when your near high pressure the increase is nonlinear.



If you never see a velocity change below 35 FPS it's a good bet your primer isn't the best choice for your combination and you need to try something else.



Let the target and the chronograph pick your load despite what you might read on the internet.

With the 6BR and 6 Dasher cartridges there are powder primer combinations that are amazingly accurate but they are range specific.

The best combination at a sea level range in California might be Varget and a CCI BR4 primer while in Montana at 6000 feet that same gun might prefer H4895 and a CCI 450 Magnum primer.

Both camps will post pictures and beat there chests telling you about all the fake wood trophies each combination has won them but you need to remember the conditions and the location may make a difference.



In my opinion accuracy trump's everything even in a hunting rifle but others will post that you go for maximum velocity and then adjust your seating depth and take whatever accuracy that produces.

Who is right is up to your own needs as plenty of deer are killed each year with factory ammo and less than stellar guns.

Would this method be in lieu of a ladder test?

Sent from my SM-N960U using Tapatalk

[LynnJr]

That method is basically a ladder or Audette test.

[choprzrul]

That method is basically a ladder or Audette test.

Your "....Audette test." remark set me on a journey. I ended up on the Dan Newberry Optimal Charge Weight page.

From my Reloader 10X test run, the velocities seemed really low to me.....so I decided to try the OCW method using Ramshot's X-Terminator powder. Still loading the Barnes 55gr TTSX to 2.300".

I intended to rather fps info for each of the 3 rounds at each charge weight, but intermittent showers disrupted my chrony, so I only made it just past the first round of each charge weight:

23.1gr 2886
23.3gr 2923 +37
23.5gr 2936 +13
23.7gr 2930 -6 node?
23.9gr 2962 +32
24.1gr 3003 +41
24.3gr 3037 +34
24.5gr 3072 +35
24.7gr 3093 +21
24.9gr 3122 +29
25.1gr 3100 -22 node?
25.3gr 3144 +44
25.5gr 3197 +53
25.7gr 3189 -8 node?

Given the above data, the Audette method seem to suggest accuracy nodes at 23.7, 25.1, and 25.7

The below pictures are of my 3 shot groups.....except 25.1 which has only 2 holes. My groups were hitting high and the first round at 25.1 was off the paper high, so I switch to the lower target....which also means my sharpie numbers don't necessarily match up the with group.

Here is an overview picture:

TargetMaster4.jpg

I'm looking for a series of groups that are reasonably small, but land on the same place relative to the bullseye.

You have to look at the very top right corner for the 25.3gr group, the bottom left for 25.5gr group, and the bottom right for the 25.7 group:

Snip33.jpg

While not super small groups, they are certainly serviceable for a hunting rifle I think.....probably most of the spread is my fault.

The thought process here is that my handloads are never going to be exactly perfect.....so I'm looking for an OCW that allows for fps/pressure variation while simultaneously having the point of impact not change. 25.5gr in the bottom left would seem to achieve that goal.

The caveat here is that I stopped at 25.7gr as I anticipated seeing signs of pressure at, or before, that charge weight. I'm guessing that seating at 2.300" is making this a bit forgiving. So.....I'm thinking I should load 3 more each at 25.3gr, 25.5gr, 25.7gr, 25.9gr, and 26.1gr......if it will fit in the case.....and then retest to confirm as I wonder what will happen to group sizes and placement going further up in charge weights.

Again, my main goal of this effort is to develop a standardized load development protocol. This Dan Newberry method seems to be quite logical. LynnJr's method above is affirmed with the -8 number at 25.7gr and the group that it printed.

This process seems to be getting very close to what I was seeking.

As always, thoughts and suggestions are welcome.

.

[Whiterabbit]

Tip: you are listing the difference in each velocity step. Thats fine, but pull up excel and plot it. WAY easier to see what is going on. Look for flat spots.

When i do this, i like to shoot 3 of each charge weight. Uses more bullets and trigger time, but it gets more data. Shoot random (not round robin). Take the average velocity and plot THAT as a line chart. Much easier to see the flat spots. Then, plot all data as dots on the same chart. This gives you an idea which loads are likely to yield tight SD as well.

If you are lucky, one of your nodes will have a wide flat and also the 3 datapoint tightly clustered. If you are really lucky, its the top node. If you are triple lucky, groups are tight and you don’t have to fix it by changing OAL.

If you have a CW range that has poor SD, then you are subject to huge velocity swings. This can lead to a false positive or false negative in your analysis posted above. 3 round screening helps protect against that. But means load dev can take 50 rounds or more. Not good if you are shooting a barrel burner...

[Whiterabbit]

A pic is worth 1000 words. Check this out. (I love this pic). Let's say I have NO idea where to go with loading. So I'm going to "overdo" the development. I take 45 rounds, a spread of 15 charges, 3 rounds each. This is beyond overkill, but it will demonstrate with certainty where the nodes are.

This is for a 105 grain 6mm bullet in 243 using an RPR (which incidentally, is for sale cheap now, shameless plug, go see my FS thread). The result when plotted as I suggested in the previous post looks like this:



Now it's more easy to visualize. You can see the flat spots. You can also use the trendline to get a sense for what velocity you can get with charge weight if you wanted to push the limits even farther. But you get something even more important than the flat lines.

Notice ES is sometimes wide across 3 rounds (this is screening only, so 3 rounds is enough. we're not doing statistics here). If I hit the slowest velocity of one CW, then the next rung up I hit the top velocity, I might come to the wrong conclusions about the node! But by using a 3 round average, my data is MUCH cleaner.

OK, so we can kinda see notes every 1-2 grains. cool. But we cna get more out of this. Note the node at 41/41.5 grains. ES is terrible. This also happens to be a common loading level for LR 243 (copper creek ammo anyone?). But for my rifle, it's a no-go, even though there is a clear node there. The uniformity is not good enough to yield good results downrange. And that's exactly what happens. So ditch it.

So which to pick? We can visualize more. Let's take the data Lynn wants you to collect and plot THAT. Just the average this time.



Clear as day now. Nodes basically every grain, but it's a low valley, high valley. Obviously, the lower the number, the better. The clear nodes are at 37.5, 39, 41, and 43. BUT, because we have minor nodes, we shouldn't ignore them, just be aware of potential for future testing. Note the node at 40 grains has a great ES. Maybe I just got lucky. Would need to test further. But it's something to keep in mind.

So, ES can also be made clearer by plotting in the same way:



Check out 41 grains. Now I know why copper creek cartridges shoot like crap in this rifle!

Put them on top of each other and you get the best data:



From this data, the conclusion is to load up some at 39 grains, and at 43 grains, for further testing. Even lucky, that 43 is coming out at warp speed!

However, in this case, (long story short) the 39 grain load had a WAY better group size at 100 yards downrange. This is actually an advantage, as 43 grains would turn my rifle into a barrel burner. But loading at 39 means I can get many thousands of rounds out of the barrel before it's done. Not to mention better recoil for spotting hits, etc. So in this case, "the load" for shooting 105 grain ELD's was 39 grains.





The story here is that good "data visualization" makes it MUCH easier to see where your nodes are. Excel is cheap, use it!

(also note that inspecting a target didn't even enter into load development until after this velocity screening, and target data wasn't used to find the nodes)

[LynnJr]

Try a group at 25.7 and see what you get.
Nodes have width to them that are case volume dependant.
With a case that shoots 30 grains of powder the nodes width will only be a half grain wide.
On a case holding more powder like a 300 Weatherby or a 50 BMG the nodes are quite large.
What that means is it is harder to spot flat spots given you might only have one round inside the node on a plot.

[micro911]

I spent 1 1/2 years on Saturdays at a range working on my loads for 308 Winchester. I based my experiments on Sierra reloading data.

I used several powders, bullets, cases, primers, various powder weight, various seating depth. Now I have a starting load that works pretty good for most rifles. It was not an easy work.

I used an Ohler 35P chronograph. It was a big help.

[choprzrul]

I find all of this quite interesting and educational. Took the time to read this paper on Optimal Barrel Time.

I then used an OBT tool to find the times for my 22" barrel:

OBT.JPG

Then.....using my QuickLoad program to check barrel times, I find that 25.1gr has a barrel time of 0.938ms and 23.7gr has 1.018ms! My previously noted 'nodes' correlate very well with OBT times.

23.1gr 2886
23.3gr 2923 +37
23.5gr 2936 +13
23.7gr 2930 -6 node?
23.9gr 2962 +32
24.1gr 3003 +41
24.3gr 3037 +34
24.5gr 3072 +35
24.7gr 3093 +21
24.9gr 3122 +29
25.1gr 3100 -22 node?
25.3gr 3144 +44
25.5gr 3197 +53
25.7gr 3189 -8 node?

It doesn't show up well in my posted pictures, but 24.9, 25.1, and 25.3 are all 3 pretty verticle and in very close relationship in their POI to the point of aim.

I believe I will load 5 each at 24.9, 25.0, 25.1, and 25.2 and test again noting velocity spreads and groups.

This is all quite fascinating!

.

[Whiterabbit]

One other thing to consider

I noticed huge amounts of variability in my sun-screen-type chronographs, that changes in ambient conditions resulted in radical differences in readings. shifts of 25 or 50 or more fps between shots that were not real.

That became a non issue when I used a magnetospeed. I'd suggest if you are looking to be the best you can, to use a magnetospeed or a labradar

[choprzrul]

One other thing to consider

I noticed huge amounts of variability in my sun-screen-type chronographs, that changes in ambient conditions resulted in radical differences in readings. shifts of 25 or 50 or more fps between shots that were not real.

That became a non issue when I used a magnetospeed. I'd suggest if you are looking to be the best you can, to use a magnetospeed or a labradar

UPS dropped off one of these today.

It's not a $1k precision instrument, but I'm hoping that it gives me good and consistent data.

.

[choprzrul]

Broke in my wife's new Savage 11 Lightweight in 6.5 Creedmoor this morning.

I then proceeded to thoroughly clean it, shoot 6 cleaning/warm up/sighting rounds, and then ran through my load ladder.....3 shots at each powder weight shot round robin.

Here is a snip of my spreadsheet results (blanks are "error" from the chrony):

Snip.JPG

That node at 41.6 grains has a VERY nice associated group:

TargetSnip.JPG

So....when I got home I ran that average FPS for 41.6 grains through my Quick Load program to check barrel time:

QLsnip.JPG

Then, when I look at the optimal barrel time chart for a 20" barrel, it is VERY close to #5:

OBTSnip.JPG

When I ponder the concept of Optimal Charge Weight (OCW), the groups for 1% up/down (41.2 and 42.0) didn't show very good POI relationship to 41.6.

I'm going to load 5 each at 41.4, 41.6, and 41.8 and then compare those 5 shot groups.

From there, I will start sneaking towards my max OAL 0.010" at a time to see how groups respond......see if I can find a nice average that more closely aligns with OCW.

I'm liking this process so far....

.

[choprzrul]

Figured I'd post the 41.2 and 42.0gr targets for OCW reference:

41.2
41.2gr.JPG

42.0
42.0gr.JPG

[LynnJr]

I would change the seating depth in 0.005 increments so you don't miss a spot.

[choprzrul]

I would change the seating depth in 0.005 increments so you don't miss a spot.

Oh wow.....they are that sensitive?

Anyhow.....I'm thinking this factory Savage with a pencil weight 20" barrel is shooting reasonable well.....

.