Seating depth prs rifle
- Thread starter Markg308
- Start date
The overwhelming majority of PRS shooters do not use a computer to tune a rifle.
RegionRat
Gold $$ Contributor
We can criticize the sweep the OP ran all we want, but where will that take us next?
Telling the OP his data is weak or statistically insignificant is not helpful since he already knows this.
The goal of his test wasn't to declare he was done. He simply asked where to try next.
He knows there is risk because it is only three shots per step. He has also been advised to take a crack at distance, as well as to try and investigate how wide this depth (and velocity) node really is.
Sometimes, these nodes evaporate, but sometimes they don't. You have to risk some shots to find out. He is merely asking where to risk spending more shots.
What else are we trying to tell him? Certainly not that he should spend 15 to 30 shots per step at such an exploratory preliminary stage or to repeat this testing?
Telling the OP his data is weak or statistically insignificant is not helpful since he already knows this.
The goal of his test wasn't to declare he was done. He simply asked where to try next.
He knows there is risk because it is only three shots per step. He has also been advised to take a crack at distance, as well as to try and investigate how wide this depth (and velocity) node really is.
Sometimes, these nodes evaporate, but sometimes they don't. You have to risk some shots to find out. He is merely asking where to risk spending more shots.
What else are we trying to tell him? Certainly not that he should spend 15 to 30 shots per step at such an exploratory preliminary stage or to repeat this testing?
My primary recommendation would be to not waste time doing any further seating depth testing, pick a jump, and party on. The objective is PRS shooting, and the seating depth test proved his load isn't jump sensitive, nothing more, so he should be satisfied to know he has a solid load ready for matches.
The point in offering statistical evaluation of his data set was meant to reveal that speculation by others here is little better than throwing a dart in the dark, rather than ACTUALLY making valid inferences from the dataset.
The test didn't offer anything which gave any evidence that any next step was worth exploring, with the exception of repeating MORE replicates of the test, IF there was belief that doing so was worth doing.
What depth node? We have what appears to be non-differentiated results from 10 thou to 70 thou.
Pick a jump, load 'em up, and party on. It's a PRS rifle. Don't overthink it. (But also don't be distracted by coincidentally small groups or coincidentally large groups).
OR...
If he really wants to get statistically differentiable data, shoot more replicates of the same test.
ETA: I'm not picking on the OP, or the groups. It's great shooting any time someone holds 3 shot groups under 2/3moa 20 times in a row. I'm just pointing to the methodology we all accepted for a LONG, LONG, LONG time for what it is - we have all let ourselves get mislead into chasing smoke, because we all TRUSTED that one small group MUST be differentiated, even if a true evaluation suggests it isn't. Sometimes we flip a coin three times and it lands head up all 3 times. That's not differentiated favor for coins to land head up - it's just coincidence. We all got duped by bad methods for a long, long time.
That’s something I didn’t know, the few guys I’ve observed seemed to rely heavily on data and wouldn’t be without the chronograph.
The chronograph helps speed up the process, but almost all of us are FULLY versed in the exceptionally simple process of running out a KD range to true our velocity in our ballistic engines, and subsequently true our BC's. It's not magic to figure out a load without a chronograph, and most of us do the same long range POI tests I've seen from your posts for years (I started doing those tests over 20yrs ago myself). But the chronograph offers an easy short cut.
RegionRat
Gold $$ Contributor
We agree on one thing, but from opposite directions.
You are correct that a 2 sigma difference isn't solid, but it only requires more testing to find out.
When the difference at stake is a good 0.6 MOA result, versus an excellent 0.25 MOA result, it is worth the try.
He has some risk to trying more shots at this step 13 depth, and/but he may or may not discover an advantage here compared to any other random depth.
While I hate to sound like a hypocrite since I am often more on your side of the arguments on load development weaknesses... In the OP's case I think it may show a good place to risk more testing which he must do anyway, so why not try there... as well as test the theory by modulating up and down to see if there are in fact any differences?
Don't get me wrong, I more agree with you than not, but the difference is I know some rigs do show an advantage at certain depths and charges that are statistically significant and repeatable. I do not agree that none of them are worth investigating. The vast majority of the new breed of PRS rifles with high quality builds and components do very well with little extra response from tuning, but it is not all of them. YMMV
The point - in entirety of everything I've written in this thread - is that the "difference" between the 0.6 and 0.25 MOA result are not at stake.
The point is that all of these groups appear to be within the same volume of data, non-differentiated.
So another way of saying this - based on that simple analysis, based only on the data we have, it appears that if he had shot the same jump for ALL 21 of these groups, odds are he would get the same number of 0.1x groups and the same number of 0.6x groups. We all know rifles don't shoot their smallest group every time, and we all know rifles shoot a span of group sizes.
So we're not talking about a .6moa opportunity vs. a .25moa opportunity at stake. We're talking about normal distribution of group sizes fired by a .37moa average rifle.
What we know about other rifles and other statistically valid experiment sets aren't what's being analyzed here. We've all seen TRULY jump sensitive combinations. The data presented in THIS thread by THIS rifle doesn't appear to be one of them.
Well, it doesn't appear to be one of them unless we choose to find confidence in coincidence.
RegionRat
Gold $$ Contributor
At this point the only difference you and I have, is I think he should go try...
He only stands to loose the ammo and his efforts to find out. Nobody said there will be anything like confidence unless he shoots more shots, but neither you nor I can guarantee success or failure unless he shoots more shots.
If he shoots and finds his rifle shooting much better at this depth, I won't take the credit or the blame.
If we tell him not to try, how will we ever know?
Go try... what?
I've said multiple times in the thread - either repeat the test to determine whether what APPEARS different is ACTUALLY different, or acknowledge there will be no difference in points on a PRS scorecard whether it's a 0.6moa rifle or a 0.1moa rifle or anything in between, pick a jump, and party on. So he can choose to try to shoot more rounds to make the test meaningful, or he can try to just go shoot matches. Will his score improve more if he shoots 60 more rounds from the bench in load dev - seeing those targets - or would shooting those 60 rounds from a tank trap in 10-15mph winds be more fruitful?
It's a PRS rifle - we're overthinking it by chasing smoke with the results we see here... We can do a seating depth test to prove we're not jump sensitive, and then know that we'll have 4-6thou longer jump every weekend and we can be happy that our load doesn't care, or we can wring our hands about deciding if a difference is a difference or not... It really should be as simple as that. If he starts chasing aggregates, sure, there's value in trying to knock a 0.3x rifle down to 0.0x. But it's PRS, pass/fail...
If the answer is "try again in a certain part of the first test," then we're chasing smoke, not science.
Myself being a guy that can’t leave well enough alone, I would have to increase the distance to the target and re shoot a depth that I felt I could read and again hopefully repeated with the mind set that if I could squeeze out more accuracy I could pass a couple more times than fail.
A shortcoming to my character I suppose.
A shortcoming to my character I suppose.
RegionRat
Gold $$ Contributor
At least 600y or more.
Suggesting he tries that depth, but goes to at least 600 yards and modulates not just the seating depth but the charge too.
He might find the charge isn't happy at distance, or it may be good. He may find the depth is insensitive, or it may matter.
Nobody is suggesting he chase smoke.... just that he takes the 100 yard stuff he has now and goes out to 600 yards and takes a look since the 100 yard results may or may not mean anything at 600.
After all, if there are equal odds that any one of his previous test data points is the same, why run any more testing at 100? But by that token, why not take a smaller part of all that, and go see if the results hold at 600?
It would mean dropping the ends of the sweep, to spend more shots at that testing in a narrower investigation.
Let’s be realistic about the thread here - we have LOTS of suggestions to chase one seating depth or another, or retest again just part of the seating depth test…
Including your last post here…
Sometimes my inside voice disagrees with my outside voice. That’s when I go pour a drank.
I guess I’m misrepresenting myself, despite over and over here saying, “don’t overthink it.”
Were it for myself, I wouldn’t do any of the analysis I did in this thread after seeing the groups on the page. I said in post #5 - “don’t overthink it,” and then when I noted some overthinking happening, I made some NON-COMPUTER DERIVED, NON-CALCULATED in #13 estimates with my Mark I Mod 0 Eyeball that there’s likely an average around .35” (calculated later to be wrong by 0.02”) and an SD around .1” (calculated later to be wrong by 0.03”), which I know would be well within a Normal Distribution for NON-differentiated groups. Doing the actual math and plotting in post #28 took less time than googling Cal’s article for the WEZ photo from the next post where I reiterated - “we’re overthinking this.”
We’ve all been guilty of picking loads based on Observation Bias when we see smaller groups on the page. Most of us have also watched a “load fall apart” for whatever reason we can’t understand… I’m convinced that happens so commonly ONLY because folks end up trusting coincidental distinctions which aren’t actually differences. Somebody told us a long time ago to do seating depth ladders like this and pick front runners from it, and not many folks question whether it actually works or not.
Were it for myself, I wouldn’t do any of the analysis I did in this thread after seeing the groups on the page. I said in post #5 - “don’t overthink it,” and then when I noted some overthinking happening, I made some NON-COMPUTER DERIVED, NON-CALCULATED in #13 estimates with my Mark I Mod 0 Eyeball that there’s likely an average around .35” (calculated later to be wrong by 0.02”) and an SD around .1” (calculated later to be wrong by 0.03”), which I know would be well within a Normal Distribution for NON-differentiated groups. Doing the actual math and plotting in post #28 took less time than googling Cal’s article for the WEZ photo from the next post where I reiterated - “we’re overthinking this.”
We’ve all been guilty of picking loads based on Observation Bias when we see smaller groups on the page. Most of us have also watched a “load fall apart” for whatever reason we can’t understand… I’m convinced that happens so commonly ONLY because folks end up trusting coincidental distinctions which aren’t actually differences. Somebody told us a long time ago to do seating depth ladders like this and pick front runners from it, and not many folks question whether it actually works or not.
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Damn it Jim, the voices generally start around 3pmSometimes my inside voice disagrees with my outside voice. That’s when I go pour a drank.
Hell Jimmy, even I'm smart enough to load a batch at touch and take a press and seater to the range and nail down the depth before pursuing charge.
But hey why overthink it right?
It is just a High$$$$ PRS rig that shoots bigger than my worst hunting rifle.
jimmymac
Jim McGregor
Most times, I take a pile of primed cases, glass vials with various powder charges, arbor press and seater die with me and just have at it.
I run an abbreviated Boyer test and if I like what I see its easy to dig deeper like right now when it is the most meaningful versus next time I come back where I will have to deal with completely different conditions.
We already had this conversation VT, RR just missed it.. your posts are well thought out factual and detailed. You’re a good shooter a great source of information and a good guy that’s willing to share
Much appreciated
Jim
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