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Posted: 8/11/2020 1:53:11 PM EDT
[Last Edit: 8/11/2020 2:02:32 PM EDT by doktarZues]
I've been loading a little over 2 years now but have not messed with any chronos. Pretty blown away with how easy to use it is and seems like it's going to be very useful. As good as this rifle was shooting doesn't look like I need it much for load work but will be helpful for ballistic/performance calculations. The pictured group was the last 6 shots at 65 maybe 70 yards (as far as I can get in my woods hidey hole), so even though the charge varied .4 (27.0 27.0 27.2 27.2 27.4 27.4) it still produced a good group.

On the "10-shot ladder" (or I suppose more accurately, just a ladder of sorts since it was no where close to 10) I actually did 2 shots for each load vs 1, then "averaged" the two shots. I started at whatever book was 24.2 I believe. Didn't include that here as it was just a steady walk up. What I found fascinating was with a simple excel line chart it clearly showed the plateau you're looking for to find the "accuracy node" at around 2300fps which was the 26.4, 26.6, 26.8 loads (I should have included that on the chart axis oh well). So going to experiment more around the plateau and also a little higher since even though it was above the "plateau" charge, that's a pretty good group that should easily be sub MOA when I can get it out to >100 yards.

Magnetospeed gets a big A+ on its first trip out, super informative for me, feels like I've opened a whole new chapter in my reloading. I got the V3 because I have suppressors in bound, it's 9 months today on the first one in queue. Just got done compiling everything and thought I'd share, no real point to the thread I guess :)

ETA - not the slightest hint of pressure signs, could definitely take this higher but Sierra has 27.4 as the max charge.


Link Posted: 8/11/2020 2:30:44 PM EDT
Great group and great data.  I need to get where I’m doing that.  I just grab a couple boxes and run out the range and see which one looks best.  

You’ve got a knack for the precision.  I need to up my game.
Link Posted: 8/11/2020 5:18:47 PM EDT
[Last Edit: 8/11/2020 5:21:06 PM EDT by SuperDutyMikeMc]
Not trying to be a debbie downer...but

http://forum.accurateshooter.com/threads/i-dont-shoot-ladders.4009071/

Second, I wouldn't make a habit of building loads based off chronographs, especially chronographs that attach to the muzzle.

I shoot ~15k rounds a year out of precision bolt guns, and chronograph everything that's not shot in matches via labradar. Velocity flat spots sometimes align with the node, but a lot of times they don't.

Looks like you got a good barrel though.  

Edit: This isn't a 'you should feel bad' type post. I've just been in your shoes, and trying to save ya some time & money.
Link Posted: 8/11/2020 7:56:39 PM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By GlockPride:
Great group and great data.  I need to get where I’m doing that.  I just grab a couple boxes and run out the range and see which one looks best.  

You’ve got a knack for the precision.  I need to up my game.
View Quote

Thx man. Still have lots to learn.
Link Posted: 8/11/2020 8:03:58 PM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By SuperDutyMikeMc:
Not trying to be a debbie downer...but

http://forum.accurateshooter.com/threads/i-dont-shoot-ladders.4009071/

Second, I wouldn't make a habit of building loads based off chronographs, especially chronographs that attach to the muzzle.

I shoot ~15k rounds a year out of precision bolt guns, and chronograph everything that's not shot in matches via labradar. Velocity flat spots sometimes align with the node, but a lot of times they don't.

Looks like you got a good barrel though.  

Edit: This isn't a 'you should feel bad' type post. I've just been in your shoes, and trying to save ya some time & money.
View Quote

No debbie downer vibes received. If there was one way or even a right way, these forums wouldn't be as active as they are. Like all things, especially this hobby, personal experience is paramount. Just broadening that a bit with this thing. I appreciate the feedback. As for the barrel, seems the TLDR on the Ruger American is they're great /if/ you get a good barrel. Seems I got one! Couldn't be more pleased with it's (completely stock) performance.
Link Posted: 8/12/2020 1:25:46 AM EDT
[Last Edit: 8/12/2020 2:01:43 AM EDT by Trollslayer]
I do not see any relationship between your data table and your plot.  

What are the units on the X axis?  


What was the point of impact for each of those shots (relative to your point of aim)?

You plotted the average values, eh.

Why did you average the two shots?  What you are thinking is a "flat spot" actually has the largest shot-to-shot variation in your data.  The averaging masks this fact.

Where is the accuracy/group size data for these shots?

In the group of six shots, which shots were which powder charge?

What cartridge is that?

Suggestions -

Try do - get rid of the averaging (see below); replot all of the data using a scatterplot rather than a sequential plot; fit a "trendline" (linear regression, fitted curve); how well does the trendline fit the data (what is the R-squared value?).

Repeat this for your point of impact data.  The POI data is what matters for your accuracy.

Link Posted: 8/12/2020 1:50:40 AM EDT
[Last Edit: 8/12/2020 1:52:41 AM EDT by Corporal_Chaos]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Trollslayer:
I do not see any relationship between your data table and your plot.  

What are the units on the X axis?  

What was the point of impact for each of those shots (relative to your point of aim)?

Why did you average the two shots?  

Where is the accuracy/group size data for these shots?

In the group of six shots, which shots were which powder charge?

What cartridge is that?

Suggestions -

Try do - get rid of the averaging; replot all of the data using a scatterplot rather than a sequential plot; fit a "trendline" (linear regression, fitted curve); how well does the trendline fit the data (what is the R-squared value?).

Repeat this for your point of impact data.  The POI data is what matters for your accuracy.

View Quote


The cartridge is in the title, 6.5 Grendel.

I think the point was to find a charge range where the muzzle velocity is consistent despite small variations in charge weight.  

The range to focus in on and continue development being where the graph flattens.

In theory that should cause a consistent POI in that range.

Of course it neglects harmonics specific to the setup.

Rather than shoot 10 groups of 5 rounds each one could shoot 10 rounds (OP did more) of say 0.2 gr. variation to find a narrower band of charge weights from which to continue load development.
Link Posted: 8/12/2020 2:00:34 AM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Corporal_Chaos:  I think the point was to find a charge range where the muzzle velocity is consistent despite small variations in charge weight. (snip)  The range to focus in on and continue development being where the graph flattens.  
View Quote


See my updated version of that post.

His "flat spot" is actually the least flat spot in his data.  The averaging masked that fact.

I suggested he focus on POI variations and find a flat spot in that data.  Once you get there, find the load with the lowest SD of muzzle velocity.
Link Posted: 8/12/2020 8:27:36 AM EDT
[Last Edit: 8/12/2020 8:27:56 AM EDT by doktarZues]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Trollslayer:


See my updated version of that post.

His "flat spot" is actually the least flat spot in his data.  The averaging masked that fact.

I suggested he focus on POI variations and find a flat spot in that data.  Once you get there, find the load with the lowest SD of muzzle velocity.
View Quote

I've seen your posts and know your experience, understand I'm not saying you're wrong, but simultaneously I don't think you're familiar with this method/what I'm trying to do. I wouldn't call it common and certainly not majority but seems there's plenty of folks that use and praise this method. It isn't the best article but what I could find quickly: https://www.carbonprecision.com/blog/10-shot-load-development-ladder

Corporal_Chaos seemed to explain it better than I could.

I wasn't sure about the averaging, but even on a scatter chart it's obvious that around the 26.4 - 26.8 range velocity flattened out, which is exactly what you're looking for. I can now work on 5-shot groups around that range, VALIDATE with POI (vs using it for initial workup), fiddle with seating depth, etc. And try and find that white wale of (consistent) .5ish moa I've been searching for since I started. Theoretically I'm saving myself some time/money/barrel etc.
Link Posted: 8/12/2020 8:31:29 AM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Trollslayer:


His "flat spot" is actually the least flat spot in his data.  The averaging masked that fact.

View Quote

Wanted to hit this part specifically. The dataset isn't the greatest because of the variation, but respective to 26.2 and 27.0, this is in fact a flat spot of velocity, averaged or not. Increasing charges does not result in corresponding increases in velocity as compared to the rest of the ladder.
Link Posted: 8/12/2020 7:27:06 PM EDT
[Last Edit: 8/12/2020 7:30:44 PM EDT by Trollslayer]
Please remember, I'm just trying to help you.  Also, let me say, that was good shooting.

I'm giving you some push back on some the statements you are making because, it appears to me, you are making a mistake in your thinking.

Whether you use the averaged or raw data, over the 26.2 to 27.0 gr range, the slope is 66/fps per grain.  That is not a small slope and certainly does not qualify as "flat".  That is what we all typically get for rifle cartridges.

I'm not trying to give you a hard time, so maybe I will just back out of this discussion.
Link Posted: 8/13/2020 5:49:05 AM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Trollslayer:
Please remember, I'm just trying to help you.  Also, let me say, that was good shooting.

I'm giving you some push back on some the statements you are making because, it appears to me, you are making a mistake in your thinking.

Whether you use the averaged or raw data, over the 26.2 to 27.0 gr range, the slope is 66/fps per grain.  That is not a small slope and certainly does not qualify as "flat".  That is what we all typically get for rifle cartridges.

I'm not trying to give you a hard time, so maybe I will just back out of this discussion.
View Quote

No man I genuinely appreciate the feedback. This is my first attempt at working a load this way. I suppose time will tell how effective it is. If I came across as defensive that was a miscommunication of sorts, I just wanted to clarify the method and goal etc.

Unfortunately I won’t be able to get loaded up and back out again for another week or so.
Link Posted: 8/15/2020 5:36:15 PM EDT
So, give it a whirl.  Let us know how it worked out.  This stuff is always interesting to me.
Link Posted: 8/15/2020 11:15:57 PM EDT
I've done this method of load development on 6 or 7 different guns and it's produced very good results. I think it's solid so long as your reloading process is really dialed in.
Link Posted: 8/16/2020 5:17:24 PM EDT
[Last Edit: 8/16/2020 5:31:27 PM EDT by doktarZues]
Got out today for a follow up shooting @ 100yds.
To recap this is a
-Ruger American 6.5 Grendel, 16" barrel
-IMR 8208
-SMK 120 seated to target 2.240 COAL and 1.730 ogive
-Federal AR Match primer
-Hornady new brass trimmed to 1.510, mouth deburred, flash hole deburred
-Fired off front bipod and rear sandbag

So the really short version is the charge in the sweet spot "plateau" area (26.7) was clearly tighter than higher charged groups. I started at 26.7 because that's where the ladder wisdom said to, but in hindsight I would have liked to have started a little lower just to have the data. I shot a few more higher charge groups not listed below (27.4, 27.5) but none were better than 1.25" and velocity gains were minimal (like an extra 10fps average between 27.3 and 27.5).  

Still a lot of variables, need a few more iterations of this before I'm a believer, but at a GLANCE, using a ladder to find the "accuracy node" appears to have some merit.

The chrono data needs some mild deciphering due to the forum editor converting the copy/paste, but for the ft/s the first two numbers is the Series and Shot-in-series, respectively. (So ignore those and look at the last 4.)



TOP LEFT
Charge 26.7
5-shot group .93


SeriesShotSpeed  
112262 ft/s  
122257 ft/s  
132245 ft/s  
142271 ft/s  
152267 ft/s  
----------------
Series2 Shots:5
Min2253 Max2282
Avg2264S-D11.6
ES 29


TOP RIGHT
Charge 26.7
5-shot group .70


SeriesShotSpeed  
212255 ft/s  
222282 ft/s  
232253 ft/s  
242266 ft/s  
252268 ft/s  
----------------
Series3 Shots:5
Min2287 Max2309
Avg2297S-D10.1
ES 22

MIDDLE
Charge 26.9
5-shot group .85


SeriesShotSpeed  
312287 ft/s  
322289 ft/s  
332295 ft/s  
342307 ft/s  
352309 ft/s  
----------------
Series4 Shots:5
Min2274 Max2320
Avg2298S-D20.6
ES 46

BOTTOM LEFT
Charge 26.9
5-shot group 1.20


SeriesShotSpeed  
412320 ft/s  
422274 ft/s  
432319 ft/s  
442295 ft/s  
452284 ft/s  
----------------
Series5 Shots:5
Min2287 Max2337
Avg2308S-D18.4
ES 50

BOTTOM RIGHT
Charge 27.1
5-shot group 1.25


SeriesShotSpeed  
512304 ft/s  
522301 ft/s  
532287 ft/s  
542311 ft/s  
552337 ft/s  
----------------
Series6 Shots:5
Min2302 Max2328
Avg2315S-D9.2
ES 26

SPLATTER TOP
Charge 27.1
5-shot group 1.05


SeriesShotSpeed  
612302 ft/s  
622317 ft/s  
632328 ft/s  
642315 ft/s  
652313 ft/s  
----------------
Series7 Shots:5
Min2310 Max2353
Avg2338S-D17
ES 43

SPLATTER LEFT
Charge 27.3
5-shot group 1.65


SeriesShotSpeed  
712349 ft/s  
722353 ft/s  
732344 ft/s  
742310 ft/s  
752337 ft/s  
----------------
Series8 Shots:5
Min2311 Max2354
Avg2334S-D16.2
ES 43

Link Posted: 8/16/2020 7:14:36 PM EDT
If this were me and I didn't have any pressure signs, I'd want to push it up a little bit. I'm seeing 28 gr of IMR8208 is popular with the 120 smk. Also, keep in mind that this powder is known to not show any pressure signs right up until the point that when it shows, it shows pretty good. So be careful with whatever you decide, but that would be my next experiment if it was me.
Link Posted: 8/17/2020 11:08:25 AM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Demphna2:
If this were me and I didn't have any pressure signs, I'd want to push it up a little bit. I'm seeing 28 gr of IMR8208 is popular with the 120 smk. Also, keep in mind that this powder is known to not show any pressure signs right up until the point that when it shows, it shows pretty good. So be careful with whatever you decide, but that would be my next experiment if it was me.
View Quote

Yep I'm going to do some more testing around my supposed accuracy node (26.6 - 26.8) and also try higher. I agree reading around the forums most people are dialing in closer to 28.0 with these. I made it to 27.5 with no pressure signs so I will try move up as well.
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