Long range load development at 100 yards.

[dottor_jeckill]

Hi to all,

i shoot, on my new remington 700 308 win, using the N140 powder and Lapua scenar-l 175 this targets, to find the right node. The load start from 39.3 up to 42, FM210G as primer, using 2.937 as COAL, just -0.020 from the jump.

I think that the shots from 7 to 10 could be the node, all are at the same height, the shots are done with 41.1 to 42 grn of N140.

I think to start from the 8 (41.4/41.5) fine adjusting the seating depth from -0.010 to -0.040 like Erik Cortina says.

Do you think, like me, that the groups from the 7 to 10 are consistent or i'm wrong and the node is another?

Thanks.

Cris.

 

[lukester]

If anyone still happens on to this long-running thread, I would appreciate feedback on my first venture into load-testing for my "new-to-me" f-open rifle. .284 Win, 700Rem trued, McMillan, Brux 32" shooting various charges of H4350 behind 180 hybrids all .020 off the lands.
Shot these into a 13mph wind coming from about my 11o'clock, although the range is surrounded by berms, walls, etc... (realized after the fact that my zero was about 1/4" low)

This was my first-ever time to: (a) shoot an F-class rifle of any kind (b) shoot off such a nice rest system - Grizzly triangle w/ Shadetree co-ax and SEB Bigfoot rear bag, and (c) use a Labradar. There were a few times early on when I didn't get the stock bumped forward against the stop. And there were two series (8 & 9) when I forgot to re-arm the Lbrdr for the first shot. Those two series had great ES potential, too, but they were way up there at the top of the test weights anyway. One other note... Beyond about 2825 or so (series 7 and beyond) the bolt was getting stiffer and stiffer. All targets have 3-shot groups, unless noted.

Do you think I have enough valid info here to pick a charge and test seating depths? Or should I run the whole thing or a range of the whole thing over again for any reason? I'm a blank slate for sure.
Thanks.

 

[DHuffman]

50.6 or 51.3 look nice to me

 

[Brians356]

[Edited] I like 51.4, ignoring the horizontal spread. Your rig seems very good.
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[SGK]

I'll chime in with one observation. Three shot groups can only tell you what definitely doesn't work. It's tempting to look at the velocity information and even the group sizes, and try to draw comparisons. BUT, key your shot data into this calculator and consider just how wide the velocity averages and SD ranges actually are at decent confidence intervals. http://172.104.26.4:4321 You can also put in two groups of shot data and see if statistically you can be confident they represent different underlying behavior. You could use the same calculator to compare group sizes as well if you had a method of calculating the center for each group and recording the lengths away from such center for each shot (an 'error' from center) and keying them into the calculator. You're sampling the performance of your rig while varying one component (powder charge). You need to understand how much confidence you can place in these (small) sample sizes.

 

[6bra1k]

I'll chime in with one observation. Three shot groups can only tell you what definitely doesn't work. It's tempting to look at the velocity information and even the group sizes, and try to draw comparisons. BUT, key your shot data into this calculator and consider just how wide the velocity averages and SD ranges actually are at decent confidence intervals. http://172.104.26.4:4321 You can also put in two groups of shot data and see if statistically you can be confident they represent different underlying behavior. You could use the same calculator to compare group sizes as well if you had a method of calculating the center for each group and recording the lengths away from such center for each shot (an 'error' from center) and keying them into the calculator. You're sampling the performance of your rig while varying one component (powder charge). You need to understand how much confidence you can place in these (small) sample sizes.

i like actual target data over anyone's math. yep i use math. but my decisions are based on the real world not a formula.
perfect example..shot group counts are way to small to be statistically significant, an indicator yes, nice to have yes. target is the real world answer.

 

[SGK]

Add more shots for each powder load and see what happens to that real world paper target. The point is you can't have great confidence in 3 shots on paper (nor 3 shot velocity data) except to dismiss something that is already bad (it's not going to get better with more shots). You don't have enough 'real world' target data to have any confidence in the small sample you have.

(You can easily have a little fun with this. Shoot, for example, 10 3-shot groups all with the same powder/setup; no variable changes. Post it only labelling each group 1 thru 10 (don't tell people there's no change in charge or other setup). I will guarantee people will start suggesting one group over another. Lastly then overlay all the shots, after all they're all the same setup, so the aim points align, building a picture of how the broader group formed when adding more shots.)

 

[jdj71]

I'm in for 51.3. 1 fps speed different between #8 and#9 smells like sweet spot to me.
Good luck JD

 

[RegionRat]

The test seems to show some horizontal shift with the charge steps. Beyond that, it is hard to say much.

For example we might all agree 1, 2, 3, are all slightly right of center, and then by 4 they are shifted left.

From here it is a little muddy in that they seem to stay on the left or center. By 7, 9, and finally 10, it appears they want to shift back to center or slightly right, but 8 wanted to sit left. Hard to say if that shift is real. The shifts may have been wind or luck.

Because we are judging shifts that are about the same size as the group, and there are so few shots to the groups, and you had an 11 o' clock wind, we might be wrong.

If you had shot that whole test, but done so at say 600 to 1000 yards, the leverage of the distance would open up a better view into the potential nodes and give the vertical ones a chance to develop as well.

I would run the same charges with three shot groups at distance and then judge where to go back and investigate. Sometimes, the best velocity stats do not come at the same speed as the best vertical nodes.

If you wait for a day with better weather, you might even be able to judge the horizontal, but at least by going to distance you will be able to read the vertical nodes much easier. I would then identify the flattest vertical node center, and test for seating depth to shape the groups. Either way, good luck!

 

[Ned Ludd]

If anyone still happens on to this long-running thread, I would appreciate feedback on my first venture into load-testing for my "new-to-me" f-open rifle. .284 Win, 700Rem trued, McMillan, Brux 32" shooting various charges of H4350 behind 180 hybrids all .020 off the lands.
Shot these into a 13mph wind coming from about my 11o'clock, although the range is surrounded by berms, walls, etc... (realized after the fact that my zero was about 1/4" low)

This was my first-ever time to: (a) shoot an F-class rifle of any kind (b) shoot off such a nice rest system - Grizzly triangle w/ Shadetree co-ax and SEB Bigfoot rear bag, and (c) use a Labradar. There were a few times early on when I didn't get the stock bumped forward against the stop. And there were two series (8 & 9) when I forgot to re-arm the Lbrdr for the first shot. Those two series had great ES potential, too, but they were way up there at the top of the test weights anyway. One other note... Beyond about 2825 or so (series 7 and beyond) the bolt was getting stiffer and stiffer. All targets have 3-shot groups, unless noted.

Do you think I have enough valid info here to pick a charge and test seating depths? Or should I run the whole thing or a range of the whole thing over again for any reason? I'm a blank slate for sure.
Thanks.

View attachment 1316309

The main point of this approach is to look for successive charge weights where the point of impact remains the same; i.e. the center point of the group remains the same. It is not about the smallest groups.

Given that, I'd be looking at the region between 50.1 and 50.6 (#3 - #5). Arguably, the one shot out (R) on Group #3 is what makes the center point of the group slightly low and right of center, where the next two group centers are located basically straight low. You also have reasonable ES values across that range. If you decide to go back and re-test within that range using a smaller charge weight increment such as 0.2 gr for all the groups (i.e. instead of 0.3 gr increment at the 3 lower charge weights as was done in this test), you might want to include 50.8 at the upper end. It looks like 50.0 to 50.8 gr would completely cover your "window".

This conclusion fits reasonably well with loads/velocities commonly obtained by F-Open shooters using this same combination of barrel length, bullet, and powder; i.e. "tuned" loads typically have velocities in the 2790 to 2820-ish fps range. I wouldn't get bogged down worrying about "statistical significance" due to the use of 3-shot groups. This approach is proven to work, and pretty much everything we do from ground zero is aimed at putting all the shots in the same hole, meaning statistics as applied to completely random samples or distributions may not be as informative as we'd like them to be. The main points here are to shoot the minimum number of shots necessary to form a "group", meaning more than 2 shots, but not so many shots as to really be testing the shooter, rather than the load itself.

The bottom line is that you have a reasonable result here that matches up pretty well with what others have generated using .284 Win loads, and that also coincides with low ES values. I'm not sure there is ever such a thing as a "perfect" test, but your results provide a rational basis for repeating the charge weight test in 0.2 gr increments across a range of 50.0 to 50.8 gr. Alternatively, you might be OK just loading up 50.5 gr and carrying out a seating depth test if you don't want to expend the rounds for additional charge weight testing. I'd personally want to do the charge weight test once more as I described to ensure that you're observing the same behavior within the apparent window and assist in making a final charge weight selection before moving on to seating depth, but I tend to be pretty conservative in this regard.

 

[darkangel_r2]

If anyone still happens on to this long-running thread, I would appreciate feedback on my first venture into load-testing for my "new-to-me" f-open rifle. .284 Win, 700Rem trued, McMillan, Brux 32" shooting various charges of H4350 behind 180 hybrids all .020 off the lands.
Shot these into a 13mph wind coming from about my 11o'clock, although the range is surrounded by berms, walls, etc... (realized after the fact that my zero was about 1/4" low)

This was my first-ever time to: (a) shoot an F-class rifle of any kind (b) shoot off such a nice rest system - Grizzly triangle w/ Shadetree co-ax and SEB Bigfoot rear bag, and (c) use a Labradar. There were a few times early on when I didn't get the stock bumped forward against the stop. And there were two series (8 & 9) when I forgot to re-arm the Lbrdr for the first shot. Those two series had great ES potential, too, but they were way up there at the top of the test weights anyway. One other note... Beyond about 2825 or so (series 7 and beyond) the bolt was getting stiffer and stiffer. All targets have 3-shot groups, unless noted.

Do you think I have enough valid info here to pick a charge and test seating depths? Or should I run the whole thing or a range of the whole thing over again for any reason? I'm a blank slate for sure.
Thanks.

View attachment 1316309

I don't think its good practice to vary your powder splits. You start with .3 splits and go to .2. In my mind that makes interpolation of those early shots harder.

Also its a good thing if your point of impact is off your point of aim when doing load dev so are not destroying the fine aim point of your target.

Are you sure about all of those shots? Did you do your part on all of them?

If your Bolt is getting heavy after 7 don't even consider them.

If I were you I'd shoot another with more shots per charge and .2 splits focused between 49 and 51 grains. You have a stable poi for 50.4 and 50.6 with good velocity stats so thats the primary area. But that lowest charge one hole followed by a tall group is interesting to me also.

Remember loads with the least vertical at 600 or 1000 yards will have some vertical present in their groups at 100. The slow bullets will be on top. If you use a shot tracking software to you know which hole goes with which velocity or you color code your noses you can recreate that groups' performance at any range using any ballistic software.

 

[lukester]

Thanks so much - to everyone who took the time to reply to my question. I appreciate it very much! And not wanting to shut down new feedback... this was just my first chance back at the computer to take a look and read through what came in so far.

 

[Brians356]

The main point of this approach is to look for successive charge weights where the point of impact remains the same; i.e. the center point of the group remains the same. It is not about the smallest groups.

A good node's point of impact does not shift vertically, as I see it. Assuming a reasonably sound setup and technique, the barrel whip is nearly all up and down, so POI moves up and down between nodes. Horizontal shift and spread are more likely to be wind. At this initial testing stage I concentrate on holding consistent vertical point of aim, and ignore any breeze.
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[Brians356]

Several have referenced a "51.3" charge weight. Which group number is that? I only see group #9 at 51.4.
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[lukester]

You're correct in that there was no 51.3 test charge. I think any reference to that weight was an assumption that it might be a good one based on what 51.2 and 51.4 showed.
Again, though, started getting increasingly hard bolt lifts beyond about test #6 (50.8+)...

 

[Papa Charlie]

To me, there is no clear transition as in a node closing up then reopening. I would redo the set using 0.3gr increments or even 0.5. This way you will see the nodes open and close much easier. Then you can refine that to 0.3gr for a narrow spread. Also, you need at least three shots per load, five would be better. But you might be able to do that when you get to the 0.3gr narrower spread.

Something else that I do is to go out as early in the day as I can to ensure there is no wind. I take a break between each set to let the barrel temp normalize as well.

If it were me, I would do the first set from 49.5 to 5.1.5 at 0.5 increments. It will give you the best visible of your next range at 0.3gr increments.

 

[Triple BB]

Still following...

 

[Brians356]

Again, though, started getting increasingly hard bolt lifts beyond about test #6 (50.8+)...

I missed the bolt lift part. Then #9 is not so attractive after all. I just love to see all holes strung on the same horizontal line, even more so for three adjacent charge weights. Even with only three-shot groups, that strongly suggests a good node.
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[lukester]

Coincidentally... I have been wondering today about how to tell the difference between a hard/heavy bolt lift due to excess pressure vs. any other reason(s)... i.e., brass sizing, etc.

I think my heavier lifts coincided w/ powder charges beyond where I have to be to find an accurate load... (lots of promise down in the target #4 & 5 range around the 50.4-50.6 wts) but would still like to know the differences for which to watch/feel.
Thanks for all the ongoing comments & advice.

 

[Ironman308]

Coincidentally... I have been wondering today about how to tell the difference between a hard/heavy bolt lift due to excess pressure vs. any other reason(s)... i.e., brass sizing, etc.

I think my heavier lifts coincided w/ powder charges beyond where I have to be to find an accurate load... (lots of promise down in the target #4 & 5 range around the 50.4-50.6 wts) but would still like to know the differences for which to watch/feel.
Thanks for all the ongoing comments & advice.

Try it with a dummy round. If it has hard bolt lift look at your sizing.