Long range load development at 100 yards.

[Jet]

I'm new to all this. It makes zero sense that you would want a string of shots that "line up vertically," since that means that they are likely traveling at different velocities (that makes sense to me). Having a load that repeatedly gives good groups would be a more reliable measure. As for seating depth, since I'm shooting an ar I'm just getting it as close to max COAL as possible. This has worked for heavier bullets, but now that Im loading lighter bullets (and the tested load data that I'm following use shorter COAL) and I'm trying to get my velocity standard deviation down and nothing really seems to work reliably. Any suggestions?

How are you measuring powder amount? Need a scale that can weigh down to .02-.04 of a grain to keep the velocity consistent.

 

[Jim R]

New to the forum and my first post. Fascinated by Erik's Load Development method. Being an old trial-and-error guy, thought I would give it a try. Attached is my initial target for review and comment on load to use for the seating depth test. Rifle is a Savage Model 12 LRP in 6.5 Creedmoor. Load particulars are Varget, 34.6 to 38.6 grains (next higher (39.1 grains) resulted in heavy bolt lift) with CCIBR4, Sierra 130TMK @ Jam-.020, Lapua Brass with 9 firings trimmed to 1.911", body sized with the shoulder pushed back just enough to allow easy bolt close (with .0005" less shoulder pushback, bolt will close with moderate resistance), neck sized w/.002" of tension (based on loaded round measurement technique) and then expanded with a Sinclair expander. Temps were in the mid 80s, humidity in the mid 60%, pressure stable at 30.14 By target 7 had significant mirage. I am thinking between 37.1 and 37.6 for next round of testing. Any input deeply appreciated.

 

[AR Shooter]

My vote is for #7.

 

[Brians356]

Split the charge difference between #6 and #7, and tune bullet jump from there.
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[David Christian]

I would reshoot this test in smaller increments (.1 to .2) between 36.5 and 38. Target 8’s speed might be chasing the higher node with that barrel length, target 4 is probably below the mid-node.

I typically try to load coarse powder tests in ~0.5% increments and fine powder tests in ~0.25% increments of total charge. Too wide and I could fly over a potential node, too narrow and I waste barrel life.

 

[Jim R]

I would reshoot this test in smaller increments (.1 to .2) between 36.5 and 38. Target 8’s speed might be chasing the higher node with that barrel length, target 4 is probably below the mid-node.

I typically try to load coarse powder tests in ~0.5% increments and fine powder tests in ~0.25% increments of total charge. Too wide and I could fly over a potential node, too narrow and I waste barrel life.

Dave,
Thanks for the input. Will perform in .2 increment and repost before moving to the seating depth test. I am considering shifting to a .25 MOA aiming point instead of the .75 used in the first test. Additionally, gonna go earlier in the morning to try to minimize mirage. My thinking is to optimize shooting conditions during the testing phases. Can't avoid heat/humidity/mirage totally on the east coast of Virginia this time of year. Thanks again.

 

[Jim R]

Split the charge difference between #6 and #7, and tune bullet jump from there.
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brians356,

Thanks for the reply. Following Erik's process to the letter, you have confirmed my analysis of the target. The one thing that concerned me was the amount of mirage I was experiencing at the end of the session. Additionally, I did not consider the size of the aiming point when choosing my target. Getting all nine charges on one target was the first concern. Once I was at the range and started shooting, I realized I should have used a smaller 'dot'. (Aim small, miss small.) On my next round of testing I will shift from a .75" dot to a .25" dot. That will fit well with my scope's center dot diameter. Thanks, again.

 

[Brians356]

brians356,

Thanks for the reply. Following Erik's process to the letter, you have confirmed my analysis of the target. The one thing that concerned me was the amount of mirage I was experiencing at the end of the session. Additionally, I did not consider the size of the aiming point when choosing my target. Getting all nine charges on one target was the first concern. Once I was at the range and started shooting, I realized I should have used a smaller 'dot'. (Aim small, miss small.) On my next round of testing I will shift from a .75" dot to a .25" dot. That will fit well with my scope's center dot diameter. Thanks, again.

Using 0.5-grain increments you may be losing some useful information. There's not much in the way of telltale vertical excursions of group centers suggesting barrel vibration nodes.
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[Jim R]

Using 0.5-grain increments you may be losing some useful information. There's not much in the way of telltale vertical excursions of group centers suggesting barrel vibration nodes.
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brians356,
Thanks for the followup reply. I agree. When using the Scott Satterlee (modified Creighton Audette) method, I use .2 to .3 grain increments for that very reason. I favor the .2 as it allows me to split evenly between two charges during the narrowing in process. When I came across the Erik Cortina (EC) method, I liked the target analysis being combined with speed data. "Examine target and find the place where consecutive groups line up vertically and ES is the lowest and speed increases the least from one group to the next." I believed my targets 6 & 7 met that requirement and you and David Christian confirmed I can read the EC Method targets correctly. I also see the benefit of David's (and now your) suggestion of repeating the test with smaller charge variances before proceeding with the seating depth testing which is what I will do. Thanks again for the replay. I invite you, David, and others to continue to follow my progress and provide input along the way. The next set of targets should be available in the next day or two.

 

[Jim R]

@JimR
If you haven’t already be sure to invest in wind flags

SPJ,
Thanks for the comment. Because of the testing being done at only 100yds (very short bullet flight time) and my home range has high side berms which usually mitigate cross range wind effect, I never really considered them necessary. But maybe the wind is not as stable as I am assuming. I will look into this. Again, thanks for the comment.

 

[Dgd6mm]

Jim R, if you were to put up a couple-3 flagging ribbons I think you will learn something, like there is slight winds even with berms in that 100 yards. Other than that, the information you've been given is solid. I like this for starters than I go to smaller increments. Once I settle on a load I will to some seating depth testing.

 

[Jim R]

Jim R, if you were to put up a couple-3 flagging ribbons I think you will learn something, like there is slight winds even with berms in that 100 yards. Other than that, the information you've been given is solid. I like this for starters than I go to smaller increments. Once I settle on a load I will to some seating depth testing.

Dgd6mm,
Thanks for the comment. I have been looking at various wind flag systems since receiving SPJ's comment but there are so many ... Any suggestions would be appreciated. I will start by getting some surveyor's tape and attaching it to our overhead baffles for starters. Was gonna shoot my .2 grain increments between 35 and 38 grains as suggested by David Christian but by the time I got to the range the mirage was very very bad so I decided to postpone until better pure testing conditions present themselves. Thanks again for the advice. Keep it coming.

 

[Kratos]

I tried this out on my 6 GT. One thing I’ve noticed is that StaBALL seems to give good groups (which isn’t the point here, I know) and very small vertical deviation, but terrible velocity spread. I wonder if I should try a different powder.

 

[Dgd6mm]

Jim Owens uses his wife's knitting yarn.

 

[comagutsa]

fine tuning the 6BRX at 200y, i did some load testing while FF my hydro formed brass and found what it like which was 35.5gr of 2209/H4350 and after a seating depth test (it likes 012 jam with the 108gr BT bergers) but after barrel finished speeding up (approx 180 rounds in this 5R Krieger and went up approx 30-40fps) i noticed i had a bit of vert at 500m and decided to run quick test the Eric way at 200y as i believe 100 is just to close, conditions weren't perfect with a approx 10mph head wind from 1-2 o'clock but i will now be using 35.3gr...


now i just need it to work at 500m and beat Rushty at our Fly state titles in a week hahaha

 

[Jim R]

Temps/humidity just won't cooperate for the rest of this week so I went back out to try to narrow things down. I think I need to explore targets 6 thru 9 in more detail. What I don't get is target 7. Is it possible that is generating a harmonic where the muzzle is on an up cycle where 6 and 8 are on a down cycle? What ya'll think?

 

[dthomas]

If you wont be overpressure i would try 38.1 38.3 and 38.5 to see if you are in a node right there at 38.1

 

[Jim R]

If you wont be overpressure i would try 38.1 38.3 and 38.5 to see if you are in a node right there at 38.1

dthomas, thanks for the comment. I will consider a .1gr incremental approach up to 38.6. In my first round of testing, that load showed no signs of pressure while @ 39.1 I had a pretty hard bolt lift. So, the threshold for pressure is somewhere between 38.6 and 39.1. A safety margin was one reason I stopped at 38.1 even tho the SD (2.2) and spread (6) were pretty good at 38.6. Another reason I stopped at 38.1 was the vertical displacement at 38.6 was going in the down direction. But maybe that was due to a downward harmonics cycle? I don't know enough about this stuff to know. I am have a blast learning, tho. Thanks again for the comment.

 

[GooseNZ]

@Erik Cortina

This thread is a great resource (well done...and thank you for sharing your knowledge)...but I have a question.

If you are developing a load for the FIRST time, in a NEW rifle, and you don't have previous data for that chambering other than what's in the load data manual, how far below the max load do YOU start?

5%, 10%, or somewhere else...

Thanks.

 

[David Christian]

@Erik Cortina

This thread is a great resource (well done...and thank you for sharing your knowledge)...but I have a question.

If you are developing a load for the FIRST time, in a NEW rifle, and you don't have previous data for that chambering other than what's in the load data manual, how far below the max load do YOU start?

5%, 10%, or somewhere else...

Thanks.

3% under the manual, as they are typically very conservative.

Or, share what combination of components and chambering you are using and just ask this forum for what others have found to be successful.