Compensation Tuning Again?.......... Sorry!

[DenisA]

David, the experience you have and the information that you pass on is amazing. You should write a book. It seems criminal that a post like that may be lost in a forum thread. I felt like I was reading a page from applied ballistics.

We're very lucky to have you involved in this forum.

Thank you for your time and wisdom, I really enjoy reading and I'm fascinated by your contributions

[DannyS]

Thanks David for re-posting your article. I was lucky enough to screen shot your original post, so I have a record of it.

Fantastic reading. Your knowledge and your preparedness to share it, is greatly appreciated.

Cheers
Danny

[williada]

Folks, you are in goods hands. DaveMc is right on the money. Me. I have already written a book, its in the blogs on this forum but thankyou for the kind words. I would rather share with people who contribute to the forum and help new shooters because that is the future of the sport. The forum is better than a book because there are so many people who contribute their experiences that the knowledge through feedback grows exponentially, not just what I might add. I just did what I was taught by some very good mentors who captured my imagination and added a few things along the way too. The cross fertilization allows people to connect the dots and for me, I am never too old to learn from anyone. There is no such thing as a dumb question but the answer has to be found in the data which through subjective thoughts (theory) becomes objective (fact). Its a process that through education you become better at because you learn from people who have done it before and build on it.

There is nothing wrong with friendly rivalry and the quips contributors make are very funny as are some of the stories.

Now to keep this post in line with the topic. A major part of controlling the recoil pattern is to relax and enjoy, then you can go about your business objectively and you will be rewarded with a higher score and enjoy it more and so it will be etched into the brain. Jim Sweet used to say, when in doubt don't if you want insurance. I have mentioned on an earlier posting that fullbore shooters could vary velocity by about 20-30 foot a second accidently with sling tension changes. This will effect the vertical and compromise muzzle lift. In the same way an unrelaxed shoulder behind the scope does it. You can take two approaches. Free recoil or lean into it with a relaxed shoulder. The latter is the only way to go with the big boomers.

Taoists might say, if you look back at the past you can become depressed. If you look forward you can become anxious but if you live for the here and now do it with reason you will be happy. Its very sad to see an unhappy Socrates or a person who dwells on what could have been. Accept it an move on. Don't repeat the same mistakes, but anyone who has not made a mistake has never learned a thing.

History does repeat itself. So I have a trivia question. Whose picture was on the flip side of a special addition of a Bryant and May match box if Pharlap was one of them? Maybe we should approach a similar company to raise our profile again with our best ambassadors?

Now AlanF, the structure you have put behind this forum has enabled this to happen and you are to be highly commended for it.

David

[AlanF]

David,

I fear that you're starting to wind up the conversation. We've only just "discovered" you! I hope you continue to contribute on topics that interest you, because as you can see, there is hunger for the sort of technical knowledge that you're imparting.

Thanks for your kind words about the forum, but the structure is nothing compared to the contents of the posts such as yours.

Alan

[DaveMc]

I must echo Alans comments here David - we are not going to let you off the hook that easily.

You and Peter may well have forgotten more about shooting than many of us will ever know. I crave interactions with the likes of you two and in nearly every conversation I learn something new. Keep it coming you have plenty of ears (or eyes in this case) soaking it up.

[DannyS]

Dave Mc, Willidia (David ), Peter Smith,

You guys need to get together, you can should be able to sell a world class book. The wealth of information you have between you, could put Bryan Litz in the shadows.

Cheers
Danny

[Tim L]

I did try to follow this, honest, but I figure I must only be 3" tall, cos for the most part it went waaaaayyyyyy over my head.

So here, - I have a plan on what I would do. It will be interesting to see if there is some sort of concurrence.

A bit of history. This is my 6.5x284. Barnard, trueflite sg, 32" 140 Berger VLD, Fed GM primers. Shot over 1500 rounds but all (bar a few testing) at less than 2850fps because it simply wouldn't group at anything over that on 2213sc or 2217. I had intended to re-chamber after NQRA Queens, but it was borescoped and still like new at the 1200 round mark. I stuffed up in my prep for QRA Queens and changed from a 0.010 jump to a 0.015 jam, but didn't load test. I paid for it.
So! It's nearing it's end, and I'll be re-chambering to 6.5 SLR soon, so I thought I'd ramp it up with 2209. Results are promising. I still have space for another gn to 1.5gn.

There was no difficulty in extraction and is no measurable case expansion.

I only did 3 round groups because,,,,, well because it's a 6.5x284. PoA was centre at all times, I adjusted the scope down betreen 47.5 and 28gn. Mirage was a bitch and I had a 5-10 blowing from rear left to front right at about 45 deg

What's the next step?

[macguru]

Well I will have a go .....

superficially, of course there seems to be nodes at 44.5 and 46 of 2209.........
with my 260 ai and 43.5gr i am getting good results and low 2900s.
So I am tempted to say chrono the 46gr load and see if you are in the same place
but pick a calm day and fire 10 shots at 300m...... I suppose the 44.5 gr load is a bit too slow
given the size of the case ..... from experience 2900s is enough velocity for that 140gr pill to give good results
out to 1000yds at least. My elevation is about 21min over my 300m zero at 1000yds,

so 300m 0
600m 8.5min
800m 16.5min
1000yd 21min

[Tim L]

Ah yes, the chrono results. I forgot to add them.

Oddly enough, the tightest group has the biggest spread. What fun

[macguru]

Nonetheless, 46gr puts you about where i am velocity wise and it seems to be a nice place.....
and your barrel lasts a bit longer than if you hot rod it

[Tim L]

I'm hearing you Mac, and I'll be doing 5 rounds at 45.8, 46 and 46.2. Here is the issue though

46 is a nice group, conveniently centre target, but its sat there on it's own. I'm pretty sure I can load to within half a grain, but what does it mean with regards to changes in environmental conditions? Cooler day, more humid, overcast. Am I likely to drop off the node?

My quandary is what's happening at 48,,,
From 46, the 46.5 group has moved up and drifting right
47 has, lets say completed the transition to the new poi
we then have
47.5, 48, 48.5. After accounting for my scope adjustment these all print groups at the same point, despite nearly 100fps difference, with 49 seeing another change in poi.

Is 48 actually the 'more stable node'? Am I walking into a negative compensation trap? Am I reading too much into this?

The other thing to consider, given minimal pressure signs and more capacity, do I chase the node that should be sitting at 50gn?
Let's not worry, at all, about barrel life, this barrel will shoot Pennants in Townsville then it's off to the shop. Is there any real advantage to driving a 140 VLD at 3100, as opposed to the 2930 or the 3020-3030 mark if I go with 48gn.

[williada]

Tim L,
Hope you don’t mind but I re-jigged your groups to examine the trends. Its a pitty you wound your scope down so I’ve anticipated where your groups would have formed. This is important to show the macro trend of the barrel. It appears your macro trend is a positive compensator and can be adapted for the long range and is also showing a great node on string 5 for the short and mid ranges.
Had your macro trend be sloping downward your barrel would have been a negative compensator.
I think string 8 is a good peak to explore for long range and I would think that high shot was the slow pill and it is a tad to the left which is good. Had it slipped a tad to the right it would be indicating your group was starting to fall off the peak node and was heading in minor negative territory. I like to tune just before the peak because as the day warms up the velocity increases so you won’t be on that slippery slope with your barrel as you seem to fall off the positive peaks quickly.
You will also notice on your lower nodes the pattern is repetitive and if you slightly increase powder you are also introducing some lateral.
May I suggest you play a little with free flight about nodes 5 or 8 to fine tune. Your barrel looks a little sensitive and perhaps movements of .003” will do it. Similarly any powder increments could be in .2’s. David.

[Brad Y]

Definitely around the 47.5gr area has potential. Seating depth and possibly a tuner/dampener could help bring it in/widen the node a little more? Any idea what the ES/SD is around that area?

[Tim L]

Tim L,
Hope you don’t mind but I re-jigged your groups to examine the trends. Its a pitty you wound your scope down so I’ve anticipated where your groups would have formed. This is important to show the macro trend of the barrel. It appears your macro trend is a positive compensator and can be adapted for the long range and is also showing a great node on string 5 for the short and mid ranges.
Had your macro trend be sloping downward your barrel would have been a negative compensator.
I think string 8 is a good peak to explore for long range and I would think that high shot was the slow pill and it is a tad to the left which is good. Had it slipped a tad to the right it would be indicating your group was starting to fall off the peak node and was heading in minor negative territory. I like to tune just before the peak because as the day warms up the velocity increases so you won’t be on that slippery slope with your barrel as you seem to fall off the positive peaks quickly.
You will also notice on your lower nodes the pattern is repetitive and if you slightly increase powder you are also introducing some lateral.
May I suggest you play a little with free flight about nodes 5 or 8 to fine tune. Your barrel looks a little sensitive and perhaps movements of .003” will do it. Similarly any powder increments could be in .2’s. David.

Thanks for that David,

If I'm reading it right, I think you made the scope adjustment compensation a string too early. Scope adjusted after 47.5. It looks like all that would do is reduce the macro slightly, but still leave it positive, just. I'll repeat the exercise and check the peak is at 47.5 or shifts to 48.

I'm running with a 0.015 jam atm, are you suggesting I put it to 0.018 and 0.012 for testing? That's going to mean trebling the number of rounds but doable.

Brad

ES And SD are on the chrono results. 47.5 was 20 and 10, but as David says, one could have simply be a dodgy pill (the pitfall of 3 round groups). After that, the next 3 strings were 7 and 4 respectively.

The good news is, the advice goes along with what I was thinking, although I wasn't looking at doing a short and long range load. That's an interesting proposition though so I'll run with that.

I take it the general consensus is not to push it to the next node? Flat primers I can deal with, holes aren't too desirable though. Unless there is a real benefit I'll bin that plan in preference to playing with seating depth.

I can always have a go after T'ville just to see how the 140 goes at that speed

[williada]

Tim, you posted while I was writing this so I made minor adjustments and added info for others.

Tim L, I am glad you posted these groups because they confirm a few things about the macro trend of the barrel if it’s a positive compensator.

If you are jamming, forget the free fight changes. That was for an off the land process. Run with what you have got. I often used the jam to induce barrel lift as I have said before. You may get a different compensation profile if you introduce free flight.

As Brad said use a tuner. A light variable one would suit your barrel.



On first observation your best groups have an extreme spread roughly 3 times greater compared to other groups extreme spreads, and in one case 4 times the extreme spread. For example, either side of string 2 (with an extreme spread of 24 fps), and is the tightest group in this section, strings 1 and 3 have extreme spreads of 6 fps. Either side of your tightest group overall, string 5 (with an extreme spread of 19) you have 12 and 13 fps extreme spread. Sort of contradicts the theory of loading for minimum extreme spread.

However either side of string 8, which is a peak node thereabouts (its between 7 and with an extreme spread of 20 you have 6 and & 7 fps extreme spread. But string 7 is not on a node and has vertical whereas string nine is on a trough node and it is tight.

It is easy to conclude that extreme spread is not a big a factor in determining group size. The group size depends on its relationship to the node.

I have also said in previous discussion, that the trough node can produce extremely tight groups and your groups indicate that and are pretty rhythmic in their application and demonstrate this too. When using this node you have to be convinced you can deliver within the parameters of this load by your reloading technique and hope your environmental window will not tip you out.

In your case the lower node (String 9), the left hand group happens to be closer to an upper node peak, and the right hand group wants to introduce lateral. Between a rock and a hard place?

The safer bet, while not as tight as the trough node, is the peak node between String 7 and String 8, because you will not have the lateral in your case and so you will not be mislead by a perceived wind change as the day warms up. You may think you will get some vertical as slow shots are tossed higher if you creep towards String 7. But in reality, because your group has a positive compensation aspect, the short range elevation you perceive in testing will be minimal at the long target distance. I think a load of 47.3 grains will be sufficient to put you on the left hand side of the node and still group well and put you on the node as the day warms up and be back far enough to prevent you slipping in the negative direction.

A further clue can be seen in your spreadsheet analysis where you graph velocity against string number. You have a flat section between strings 7 and 8 where velocities don’t change much. Now all you need to do is identify the nodal peak, which you can do by laying out your groups side by side as I have. Then draw the channel about the major peaks and troughs. The channel shows the macro picture or the compensation profile of the barrel. Next, draw the dashed line following the sine wave of peaks and troughs for the micro picture. This will show you the best area to load when you consider the node and group patterns either side.

If you look up the weather conditions on the BOM site, and you reckon they are stable, be a risk taker and use the lower node, you might be pleasantly surprised. David.