Maybe the endless hold of charts and graphs, I guess we’ll find out.
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How to chart load development results
- Thread starter slowbalt
- Start date
Long range load development at 100 yards.
I found this target, and I think it's a perfect example of how some people might choose the wrong load because they fell in love with a group without reading the groups properly. This target was shot with my 6.5x47 Lapua and 139 gr. Lapua Scenars with VV N550 powder. At plain sight, 38.5 gr...
forum.accurateshooter.com
wkndwarrior
Silver $$ Contributor
To sort of combine the advice of all others mentioned above, I'll usually do a load ladder with 3 shots on a fresh bullseye for each load. Once I move along to a more focused charge range I'll step to 5 shot groups. For the OP, something that I've found beneficial is writing out the load and range data on the target and saving a picture of it in my spreadsheet. It really helps me recall where I was headed since I have reloaders ADHD and almost never finish one work up at a time. It also helps remember when your accuracy node and sd maybe don't align perfectly. I made some address labels to make recording data less time consuming. Sometimes I'll also save pictures of the fired cases or anything else that might be relevant in the spreadsheet.
Attachments
What brand chronograph are you using ?
Some have apps to help foremat data .
Very interesting!!! I've read grafts and charts most of my life!!! Where the 3 shot velocity spread is small (almost making a single dot on the graft), they occur where the slope of the average line approaches Zero and lay in the valley of the 2 adjacent powder charges!!! Looks like the node is between 26.3 and 26.5 since the average line segment there is the flatest!!! I would run 5 shot strings at 26.0, 26.2, 26.4, 26.6 and 26.8. Record velocities and check target grouping!!! The secret to precision reloading is consistency in powder charge vs velocity spread which is proportional to the consistent pressures!!!
BILL
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First time out with my Garmin Xero.
This may help you.
Garmin ShotView™ App
The free ShotView smartphone app is designed to work with your Xero® C1 Pro chronograph.
www.garmin.com
I don't have a clue what these graphs show that is usefull.
Neither do I.
To politely coin a phrase from @Varminterror , chasing that rabbit won’t get you fed. The guys that shoot some of the smallest groups in the world just use a paper target to accomplish load development and only consult a chronograph as a side note.
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Jeff Porter
Gold $$ Contributor
Small sample size statistics can mislead you. The range of expected values for each powder charge in a 1-5 shot test at each charge will cover enough velocity that all of this will become a straight line over time. Most statistics require a sample size of 30 per data point to get a full picture of the possible distribution of the values. The pure physics of adding more propellant to the same case volume and not seeing a linear increase in velocity goes against intuition.
I used to look for flat spots or nodes but have gone to looking for minimum velocity needed for the bullet to perform at the distances required ( expansion for hunting loads, supersonic at 1k for target shooting etc. ) and the maximum load when pressure occurs. If a powder and bullet give me velocity in that range and are about 1.0 grain under pressure sign, I will look for group size and shape and then tweak with a jump test if one shows some promise. I am quicker now to try another powder or another bullet rather than hunting up and down for a charge weight and bullet seating depth and getting a good result one day and not so good the next with the same load.
The reality has shown that where I used to see flat spots are generally 80-90% max loads and these are the case fills that tend to work if a powder/ bullet combination will produce good results in your barrel.
All I am saying is what others have said .. let the target tell you what works. If it says it isn’t working, don’t waste components and barrel life making a silk purse out of a sows ear.
If it is … get a barrels life number of those components and enjoy shooting an accurate rifle.
I used to look for flat spots or nodes but have gone to looking for minimum velocity needed for the bullet to perform at the distances required ( expansion for hunting loads, supersonic at 1k for target shooting etc. ) and the maximum load when pressure occurs. If a powder and bullet give me velocity in that range and are about 1.0 grain under pressure sign, I will look for group size and shape and then tweak with a jump test if one shows some promise. I am quicker now to try another powder or another bullet rather than hunting up and down for a charge weight and bullet seating depth and getting a good result one day and not so good the next with the same load.
The reality has shown that where I used to see flat spots are generally 80-90% max loads and these are the case fills that tend to work if a powder/ bullet combination will produce good results in your barrel.
All I am saying is what others have said .. let the target tell you what works. If it says it isn’t working, don’t waste components and barrel life making a silk purse out of a sows ear.
If it is … get a barrels life number of those components and enjoy shooting an accurate rifle.
i've had my garmin for a while now and keep forgetting there is an app, thanks for the reminder i'm going to download it now before i forget againThis may help you.
Garmin ShotView™ App
The free ShotView smartphone app is designed to work with your Xero® C1 Pro chronograph.
Good point and I totally agree about the importance of "consistency in powder charge vs velocity spread", which the target tends to represent. Rather than graphs telling me about velocity consistency, it's velocity SD's that tell me which loads are the most consistent. Though the lowest SD's seldom coincide with the best groupings on paper, it is indeed ALL about consistency for every aspect.
If the slope of the average line is repeatable, then I'd say that approach to determining a "node" would certainly be valid. Once in a while one will find a couple that repeat, but always, the more one does the more one finds no consistency for that zero slope.
I always try to record velocities when target shooting, as the velocity data I collect only tells me how well I'm doing with my reloading. It's only the target that tells me which load is working and which isn't. Velocity data does help me with getting to the right barrel timing, especially when I have a good idea where I need to be with a particular barrel configuration, powder and projectile. Also, having plenty of velocity data helps with getting on target when long range shooting.
RegionRat
Gold $$ Contributor
See post #5 and #13 in this string.
After pointing out that the idea of using a chronograph to plot "velocity flat spots" was misguided advice...
The OP was shown that his chrono data could still be turned into useable data and the graph he requested.
Once several forum members inform a poster that they should check into the issues, it is time to move on.
The utility of a charge versus velocity plot is not for finding the optimum load, it is to cross check the load against expectations and predictions and then for adjusting internal ballistics models. As such, it is recommended that folks don't spend too many shots on wide velocity sweeps since it would waste a considerable amount of their resources on charge steps they would never use and then still require more.
It isn't possible to explain internal or external ballistics in a thread, nor can we teach one method of load development that can be used for everything, but we can say that dumping rounds over a chronograph to look for velocity flat spots is misguided. Then to be helpful, we try to explain how to process the data into the graph as requested. Carry on.
I'm sorry!!! I did get off of the subject of plotting and grafting of the chrony data!!! The plotting of that graft showed factors of load development that just stood out like a soar thumb!!! But, I said it looks like a node, didn't say it was the node!!! And yes, in my study of Statistics, a 3 shot string is not a good population!!! That is why I was suggesting a 5 shot string using the even numbered tenths of a grain!!! This could still lead to replication of the 1st test data!!! And I total agree that target groups are the final say!! I'm saying this an Engineer, we can use other tools to achieve that goal!!!
By the way, I do have 105 credit hours of pure applied science!!! Mostly in physics and mathematics next!!! Using calculus, I could find the min/max points, point of inflection, and critical point of the plotted graft!!! My study in Thermodynamics (the study of heat energy) is the closest study to understanding internal ballistics!!! Heat is the result of the combustion (explosion) of the powder!!
A firearm has about the same characteristics of a 4 cycle (non mechanically linked piston) engine that drives that bullet out of the barrel!!! Not the 2 cycle, diesel, or rotary engine of which I have studied in thermo!!!! I could set down and calculate the peak temperature at a given peak pressure!!! You would be amazed by the temp of that plasmatic gas!!!
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RR posted;
Once several forum members inform a poster that they should check into the issues, it is time to move on…
Yet the thread continued in repetition, I suppose one of the good things about living in America is being able to reply on an open forum as did at least eleven members on this thread.
As long as the truth even lightheartedly is presented without being rude or insulting there shouldn’t be a problem presenting one’s view.
Once several forum members inform a poster that they should check into the issues, it is time to move on…
Yet the thread continued in repetition, I suppose one of the good things about living in America is being able to reply on an open forum as did at least eleven members on this thread.
As long as the truth even lightheartedly is presented without being rude or insulting there shouldn’t be a problem presenting one’s view.
The spread between a few similar loads is extreme. Doesn't make sense.
RegionRat
Gold $$ Contributor
I support that last line and hope you didn't think I was implying a problem with anyone else.
I am somewhat dyslexic and a horrible writer, so apologies if that sounded like it was directed outward. What I meant to say is I should move on, so it was meant to mean me not you or anyone else. Carry on.
Who's digging the hole?
6.5 forever
Silver $$ Contributor
One thing is certain. Charting nodes will show there is no such thing as nodes.
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