Bullet Jump Research: Executive Summary & Load Development Tips

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This is the last post in a series of articles focused on bullet jump research that has been conducted more than two years by Mark Gordon of Short Action Customs (Who is Mark Gordon?). In this post, I’ll provide an executive summary of what we covered and provide a few tips for how to apply this new knowledge in our load development.

The first
article provided a comprehensive overview of what 10+ of the most respected
books and reloading manuals had to see about bullet jump and laid the
foundation of what bullet jump is, along with other concepts like freebore,
lands, seating depth, etc. Everyone from accomplished scientific researchers to
world-champion shooters suggested either seating bullets into the lands or minimizing
jump to within 0.020” of the lands or less for the best precision. Benchrest
World Champions and other experts explained that when seating bullets close to
the lands, changing bullet jump by 0.002-0.005 inches can potentially have a
dramatic affect precision.

Then we looked at How
Fast Does A Barrel Erode?, which focused on how quickly the lands of a
rifle barrel usually erode for popular mid-sized cartridges used in precision
rifle matches, like the 6mm Creedmoor, 6 Dasher, or 6.5×47 Lapua. There we saw
it is common for that lands of a barrel to erode by 0.004-0.007” every 100
rounds.

Barrel Wear Erosion of the Lands

That means if we’re in a major PRS/NRL match where you fire
200 rounds over two days, by the last stage our bullet jump will be
0.008-0.014” more than it was on the first stage!
So, if the experts are
saying that changing bullet jump by just 0.002-0.005” can have a “dramatic”
impact on precision, what will 2-7 times that much do?

It seems we usually apply best practices that were
established in other shooting disciplines, but if we’ll be in precision rifle matches
that require 100-200 rounds, maybe our priorities should be different. In other
types of competitions, like Benchrest, shooters may literally load their ammo
at the range as they’re shooting. Extreme Long Range (ELR) has much
lower round count. F-Class and other competitions allow sighters, so if your
vertical shifted you just adjust a click or two to center your group before you
fire your shots for record. However, in PRS/NRL matches first round hits matter,
round counts are high, and we don’t get to fire sighters or recheck our zero.

What if instead of looking for the one exact bullet jump
that provides 100% optimal precision and having to constantly adjust the
seating depth as the lands of the barrel erodes, we instead looked for the
bullet jump that is very forgiving AND still provided good precision over a
wider range of jumps?

Now let’s think about the guys who aren’t reloading: If a
shooter plans to simply shoot match-grade factory ammo, could we optimize the
freebore of the chamber to be a bullet jump that would continue to provide good
precision over a longer period of time as the barrel wore? I recently measured
400 rounds of various match-grade factory ammo (for an upcoming test), and it’s
not uncommon for the length from the base of the case to the ogive of the bullet
to vary by 0.008” or more even in within the same box of “match-grade” ammo. So,
it seems like those guys using factory ammo might have similar priorities.

What if absolute peak precision might not be the only
priority we are trying to balance?
I totally understand that in some
shooting disciplines, like Benchrest, optimal precision is the absolute highest
priority and nothing else is even a close second. But what if we came at this
from a different angle and tried to see if there was a way to balance
priorities of both precision and a forgiving bullet jump?

Bullet Jump Load Development Goal For Precision Rifles
Mark Gordon - Short Action Customs

That line of thinking is what led Mark Gordon to start testing bullet jump. Mark builds custom precision rifles at Short Action Customs and he brings an obsessive approach to optimizing every facet of the rifle system. His methodical and analytical approach eventually led to research on the ammo his rifles were being fed. It is important to understand Mark didn’t start this research with a theory to prove. He simply wanted to know if there were any small improvements he could make to the chambers on his rifles to improve their performance over his competition. Was there something that seemed to work well across a wide range rifles? Mark started experimenting bullet jumps and collecting data over two years ago, and some of his results seem to challenge conventional wisdom.

Mark used an approach similar to the Audette Ladder Test and OCW method, but the goal was to not find the most forgiving powder charge weight, but the most forgiving bullet jump. He wasn’t looking for the specific bullet jump that grouped the best, but the largest window of bullet jumps that provided a similar point of impact. That means the rifle would be more consistent from the start of the match to the end of it or could shoot a particular kind of match-grade factory ammo really well for a longer period of time.

Here is how Mark performed what he calls the 20-shot jump test:

  1. Carefully measure the bullet seating depth required for the bullet to very lightly contact the lands (i.e. 0.000” jump, but not jammed into the lands). Watch my video showing Mark Gordon’s method on how to do this.
  2. Load up 20 identical rounds, except vary the bullet seating depth in 0.005” increments. #1 = 0.000” jump, #2 = 0.005” jump, #3 = 0.010” jump, … , #20 = 0.095” jump.
  3. Fire the rounds at 600 yards, recording the point of impact coordinates for each shot with an electronic targeting system and muzzle velocities with a LabRadar.

We then analyzed the vertical dispersion of the data he
collected. The goal was to find a range of bullet jumps that all had similar
vertical points of impact (POI) at distance. I explained how we took the target
data and turned it into the charts in detail in the Bullet
Jump: Is Less Always Better? post, and I’d encourage you to go read that if
you haven’t already. I won’t be repeating all that here.

The Results For Berger
105 Hybrid

Mark has repeated the same 20 shot bullet jump test using
the Berger 105gr Hybrid over 10 different rifle/load configurations. That
included 5 different 6mm cartridges: 6×47 Lapua, 6mm Creedmoor, 6 Dasher, and 6
BRA. Those rifles also had a variety of actions, stocks, chassis, brands of
barrels, contours, and twist rates. (Read
more about the rifles tested here.) While there was a lot of variation in
the rifles tested, there seemed to be some similarities in terms of performance
based on bullet jump.

The chart below graphs the results for all 10 rifle
configurations, meaning it represents data points for 200 shots fired with the
Berger 105 Hybrid bullet. The gray area is widest on the left side of the chart
and it narrows as you move to the right, with the tightest area around 0.070 to
0.080” of bullet jump. That means over all 10 rifle/load configurations, the
vertical extreme spreads appear to be the tightest at 0.070 to 0.080” of bullet
jump.

Bullet Jump for Berger 105gr Hybrid with Trend Lines

Another interesting thing about the chart above is it appears to be saying that when you have minimal bullet jump (0.000-0.010), that is where it appears to be least forgiving in terms of changes in bullet jump. You can tell that by the widest area of gray on the left of the chart. That means if you start off with 0.000” of bullet jump, after you’ve fired 100 rounds and the throat eroded by 0.005”, and therefore you’re jumping 0.005”, you may very likely experience some vertical stringing, and in some cases it looks significant (over 1 MOA).

We also looked at what the average vertical extreme spread
was over two ranges of bullet jumps:

  • 0.010” wide range of bullet jumps: What
    you might expect the lands to erode over 150-250 rounds with popular
    precision rifle cartridges
  • 0.020” wide range of bullet jumps: What
    you might expect the lands to erode over 300-500

We looked at the results for
the Berger 105 Hybrid Bullets in detail (view here),
but we also published research data Mark collected across 9 different
rifles/load configurations using Hornady’s 6.5mm 147 gr. ELD-M bullet, and data
over 6 rifles using David Tubb’s 115 gr. DTAC RBT bullet (view detailed results for those 2 bullets).

Below are summaries of the
average vertical extreme spread over all 3 bullets for both a 0.010” wide
window of jumps, as well as the 0.020” wide window of jumps. These two charts
basically summarize all the research data presented over the last two posts,
and allow you to see the trends of the bullets side-by-side. In this visual,
the lower the line the better, because that indicates a smaller extreme spread.

Vertical Extreme Spread Over 0.010 Bullet Jumps
Vertical Extreme Spread Over 0.020 Bullet Jumps

While there are slightly different patterns between each of the bullets, it does appear none of the bullets have the most forgiving bullet jump under 0.030”. The most consistent vertical POI over a wide range of bullet jumps appears to be at 0.040” or more bullet jump. Jumps that have traditionally been considered absurdly long, like 0.080” or more, actually seem to produce less vertical shift in POI as the barrel wears than when the bullet is seated near the lands.

So What Does All This
Mean?

Remember, Mark wasn’t looking for the specific
bullet jump
that grouped the best, but the largest window
of bullet jumps
that provided a similar point of impact.

This research is NOT claiming you can’t get extremely
precise groups seated close to the lands or even into them. Of course, you can!
However, what the data does appear to indicate is that if you are seating
bullets 0.030” or less from the lands, you could experience a vertical shift in
point of impact if you don’t tightly manage your seating depth and adjust it
regularly (e.g. every 100-200 rounds). While minimal jump may produce smaller
groups than if you were jumping 0.060” or more, that isn’t necessarily a hard
and fast rule either.

Here is the question we were original hoping to answer: What if instead of looking for the one exact bullet jump that provides 100% optimal precision and having to constantly adjust the seating depth as the lands of the barrel erodes, we instead looked for the bullet jump that is very forgiving AND still provided good precision over a wider range of jumps? This research seems to make a strong case that the answer to that is found at longer bullet jumps. However, the specific “sweet spot” seems to vary based on the specific type of bullet you are using.

I created the illustration below to try to help people
understand this concept. I admit this is likely grossly over-simplified, but it
seems helpful. The green dots are intended to represent a group at some point
in time, and the red dots are another group fired after the lands eroded 0.010”
over 150-250 rounds fired.

Vertical Shift in Groups

The example above literally came from the test results for 115
DTAC. The 0.8 MOA Extreme Spread shown on the left is what was measured on
average over 6 different rifles when the bullet jump was changed from 0.025” to
0.035”. The 0.3 MOA shift on the right is what the ES was for bullet jumps from
0.075” to 0.085”. Now, that does not mean the size of the groups reflects what
happened, because we didn’t test group size at each specific jump.

The truth is, we could easily miss large patterns like this
which occur over round counts of 100 or more. While we may fire a couple of
groups in a row, we don’t do that over 100-200 rounds in a row. If you are
shooting precision rifle matches where there aren’t sighters, round count is
high, you can’t recheck your zero, and you’re trying to make first round hits on
small targets at long range … this seems like relevant and actionable insight!

Support From A
Statistician, Top-Rank Shooters & Industry Pros

As Mark began sharing this with friends in the shooting
industry, he quickly met some skepticism on whether the data he collected was
reliable or simply random patterns. Mark also wanted to know how much
confidence he should have in the results, so he enlisted professional help in
reviewing, analyzing, and processing the data. Earlier this year, a
statistician named Walter Meyer analyzed all of the raw data, and he concluded
that the findings showed a “strong statistical improvement in the bullets
ability to hold tight vertical at distance” and “statistically significant
conclusions are appropriate.”
He calculated p-values less than 0.05 with
two different approaches, meaning there is strong evidence that the patterns
aren’t random. Walter was careful to add, “Extrapolations to other tests,
bullet type and environmental conditions must be made with caution by the
subject matter expert.” That means we shouldn’t assume the results for a
particular bullet represent how other bullets might behave, which is an important
point.

Scott Satterlee

As I shared in the first post with results, after Mark started sharing his finding with a couple of the top-ranked PRS/NRL shooters, they tried this for themselves and are now believers. One of those is Scott Satterlee, who has placed in the top 10 in both the PRS and NRL in the overall national standings in recent years and is clearly one of the best shooters in the country. Over the past two years, Scott has experimented with freebore and bullet jumps all the way out to 0.250 inches! He is now on his 5th barrel since he’s been experimenting with longer bullet jumps and said, “This isn’t something that I’m still wondering if it’s true or not. After 5 barrels, I know it’s real. There is a real improvement and benefit here.

Accuracy International

Even more recently, a friend in the industry reached out to me after reading my articles on this research to let me know it aligned with some extremely in-depth research they’ve conducted. Scott Seigmund is Vice President of Accuracy International of North America, and here is what he shared with me:

“A few years ago, we did extensive data analysis on 338 rifle test groups involving two significantly different freebore lengths. The test involved 25 different rifles (50 in total). One group of 25 rifles had a standard CIP 338 Lapua chamber while the second group of rifles had chambers with a large increase in freebore. The data was analyzed by David O’Reilly, our operations manager and statistical expert. The results even surprised me with an increase in accuracy of 19% with the 300 grain bullets jumping about 0.100″. The test was done using the same lot of 338 Lapua 300 grain Scenar ammunition and over 2500 shots collected. While I would love to claim credit for this “discovery” it was basically gifted to us by Wade Stuteville. Wade was on to this bullet jump thing a long time ago and has done a lot of testing in this area. He’s one of the most intelligent people I know and has no ego about what he knows. Just a great, caring, and giving person.” – Scott Seigmund

Wow! The test involved 50 rifles and over 2500 shots! That sounds like some serious research, and I’d think those results are conclusive. Thank you, Scott, for your willingness to share that with the rest of us!

In further conversations, Scott said as they’ve also done considerable research on the 300 Norma Mag as they were prepared to submit their rifle for the SOCOM Advanced Sniper Rifle contract, and they found longer bullet jumps improved performance on that cartridge also.

Wade Stuteville

Over the past few months, I’ve had a ton of conversations with industry pros about bullet jump, and multiple people have brought up Wade Stuteville as someone who had originally told them about the performance you can potentially get at longer jumps. Wade is a veteran shooter who was the PRS Overall Champion several years ago, and he is also one of the most respected gunsmiths in the country (read more about Wade). I’ve known Wade for several years, so after hearing his name come up so many times, I gave him a call to get his perspective.

“From what I’ve seen the big, magnum cartridges all like to have longer jumps. But, even our match cartridges (like the Creedmoors, x47 Lapuas, BR’s, Dashers) have that spot around 0.010-0.020” bullet jump where they shoot good, but usually there is another spot way back that is much wider and more forgiving. A lot of bullets don’t seem to shoot as good in that 0.020-0.050” range, but then come back into a place around 0.050+ inches where you might be able to move the jump from 0.050 to 0.100” and it shoots good everywhere.” – Wade Stuteville

Wade went on to say that when the Berger 105 Hybrid bullets first came out, he started shooting them from a 6×47 Lapua and was getting great performance seating them close to the rifling, and he’d consistently keep them tuned with very minimal jump. After a match he’d clean his gun, remeasure the distance to the lands, and then take any ammo he had left over from the match and bump his bullet out to the new seating depth to keep them close to the rifling. Wade went on to say that he first discovered the longer bullet jumps on accident. He had two 6×47 rifles that were basically identical except one had more rounds on it than the other. One day he shot the ammo that had been tuned for the chamber with less rounds on it in the other rifle, which meant it was jumping much longer – and it performed as well as anything he had shot! Wade said that is what triggered him starting to experiment with jump. He discovered on his 6×47 rifles he could start off jumping the 105 Hybrid’s around 0.080” and never have to change the seating depth over the entire life of the barrel and it’d perform great the whole time. Wade explained, “Over the life of the barrel, my jump might change from 0.080” to 0.130” or something, but it never really comes out of tune. And I’ve had a lot of cartridges that have been that way in the past.”

While much of this seems to be counter to “conventional
wisdom” (which I outlined in the
first post), there sure seems to be some pretty compelling evidence from
this research and the experience of other respected sources in the industry.

Load Development Tips

I originally planned to make a recommendation for how to integrate bullet jump into your load development. However, I’m still experimenting with the best way to do that myself. So instead of prescribing how to go about it I will simply offer a few tips based on this research data and share suggestions from others in the industry. Armed with that information, you can make an informed decision on how you might try this out for yourself in your load development. Also, if you have a good way you test jump during load development, please share that with the rest of us in the comments!

Important: Adjusting seating depth to match your rifle’s throat/freebore and maximize accuracy “is fine, but bear in mind that deeper seating reduces the capacity of the case, which in turn raises pressures. Going the other way, seating a bullet out to the point that it actually jams into the rifling will also raise pressures.” – Sierra Reloading Manual

Measure Your Distance to The Lands With A Precise Method

Until a few months ago, I was measuring the distance to the lands like most people do. I thought it was accurate, but I was off by almost 0.100” in some cases! No joke. It turns out you can seat a bullet well into the lands without it leaving marks on the bullet or getting stuck in the rifling. Measuring the distance to the lands in a way that is accurate and repeatable is harder than it seems. There are only two methods I know of that allow you to measure the distance in a way that is repeatable within +/- 0.002”; Mark Gordon came up with one and Alex Wheeler teaches another. You can learn more about both on this page: How To Measure The Distance To The Lands On Your Rifle Barrel.

If you take just one piece of advice from all this, I might
suggest it be to try this measurement method. I bet the results surprise you.
Honestly, if you are not measuring the distance to the lands with one of these
methods, I bet you aren’t testing what you think you are.

Measuring CBTO vs COAL

If you are concerned with bullet jump, you need to measure from the base of the cartridge to the bearing surface of the bullet (i.e. CBTO or Cartridge Base To Ogive), not from the base to the tip of the bullet (i.e. COAL or Cartridge Overall Length). Even if bullet tips were completely uniform (and they never are), remember that bullet jump is the distance a bullet travels before it’s bearing surface touches the rifling in the barrel – so measuring CBTO (Cartridge Base To Ogive) is a much better way to ensure that jump is uniform. (Read more: Article from Bryan Litz on CBTO vs. COAL)

COAL vs CBTO (Cartridge Length To Bullet Tip or Ogive)

To measure this, you need a caliber-specific bullet comparator.
I use one from Hornady, and you can get it in a kit with 14 caliber inserts that covers all major
calibers on Amazon.

Establish Seating Depth, Then Powder Charge

Mark tested 3 different loads for the 6.5mm Hornady 147 gr.
ELD-M from the same rifle, and all of them resulted in a very similar “sweet
spot.” Regardless of the shooter, order the shots were fired in, or amount of
powder used, the data showed a sweet spot around 0.060” of bullet jump each
time the test was run (read
more here).

Alex Wheeler, owner of Wheeler Accuracy and a
respected gunsmith who has built some of the best shooting 1000 yard Benchrest and
F-Class rifles, seems to agree with this idea:

“From my experience powder charge will not drastically affect the correct seating depth. Meaning if you change your powder charge the gun will not go from preferring a .010 jump to a .060 jump. It may move a few thousandths, but I think you can use any powder charge you want to rough in on seating depth.” – Alex Wheeler

After doing more than 2 years of research on bullet jump, Mark Gordon believes bullet jump is a more course adjustment to a load than powder charge, meaning a small tweak to bullet jump can often has a larger impact on performance than a small tweak to powder weight. I remember where I was when I first heard Mark propose that, because it was so foreign to my way of thinking. I’d been approaching it from the other direction completely. However, I can’t say that doesn’t fit my experience, and if that is the case then it makes sense to start with the most course adjustment before we move to further steps to refine a load.

Scott Satterlee explains that when he does load development,
he starts with the same powder charge weight that worked best in his last
barrel or if he’s working up a load from scratch he’ll simply start with a powder
charge he knows is safe. Then here is his two-step load development process.

  1. Bullet Jump for Group Size/Shape: Scott
    tests various bullet jumps to find the one that produces the smallest vertical
    extreme spread at long range. He prefers to tune a load at either 800 or 1000
    yards. In this step, he is 100% focused on group size and shape. He is not just
    looking for a small group, but the shape is important too. Scott believes a
    group in the shape of a triangle is great, and one that looks like the 5 on
    dice is outstanding. He does not like to see a group that is short and wide,
    even if the spread is tiny. Scott said from his experiencing, following a group
    like that leads to the road of destruction, because it is deceptive and won’t
    be a consistent performer long-term like a group in those other shapes. Scott explains
    that what you’re looking for is not just a small group, but an even
    distribution in the shots within the group. From a statistical perspective, I
    think Scott is saying that you want a very small Average Distance To Center
    (ATC), which is also sometimes called mean radius. That doesn’t mean you can
    ignore the extreme spread, but he doesn’t simply pick the group with the
    smallest extreme spread. (I’ll touch more on the specific jumps Scott tests
    in the next section below.)
  2. Powder Charge for Lowest Velocity Extreme
    Spread:
    Once Scott has found the optimal bullet jump, he starts varying the
    powder charge with the goal of finding the lowest extreme spread (ES) in muzzle
    velocity. In this step, Scott isn’t looking at group size and even said he
    might just fire the bullets into a berm, because he is 100% focused on finding
    consistent muzzle velocities. While many shooters reference the muzzle velocity
    standard deviation (SD), Scott prefers to use ES as his guiding metric. He says
    occasionally you’ll have one shot out of a long string be very different, and
    SD glosses over that anomaly more than ES does, but that kind of thing could result
    in a miss in a match.

For more details on Scott’s approach to load development, I HIGHLY recommend listening to a recent podcast where he shares all the details. It is VERY interesting! Modern Day Sniper Podcast: Scott Satterlee & Handloading. The podcast is hosted by Phil Velayo and Caylen Wojcik, who are top-ranked precision rifle shooters and they know what they’re talking about. At SHOT Show earlier this year, Scott Satterlee, Mark Gordon and I had a long conversation, and this podcast is very similar to listening in on our conversation at SHOT. Scott has an unorthodox/pragmatic approach to load development, which I won’t attempt to repeat here. I promise it will challenge how you think about this stuff and I bet you walk away with at least one or two good ideas for how you could improve your own approach.

What Jumps to Test

Let’s first look at the data from Mark’s bullet jump research. Below is a little different view into the same data we’ve looked at over the last two posts, which helps visualize where the “sweet spots” are for the three bullets Mark has compiled considerable data for:

Vertical Extreme Spread By Bullet Jump Range

You can see all of the bullet jumps that produced consistent vertical POI at long range were at least 0.040” from the lands or more. Most of the time it was actually 0.050″, which is also what Wade Stuteville said his experience was. Remember, this isn’t saying you can’t get tiny groups at shorter bullet jumps, but the data is simply showing that shorter jumps are less tolerant of changes in bullet jump. At least for these three bullets, jumps under about 0.040-0.050” are not as forgiving and consistent as the distance to the lands changes.

So if finding a forgiving bullet jump is a priority for you, the data seems to be suggesting you start testing around 0.040” and go out from there. While Mark’s testing was limited to bullet jumps out to 0.095”, Scott Satterlee has experimented with bullet jumps out to 0.250” on his 6mm Creedmoor – and Wade Stuteville said he’d also tested cartridges out 1/4 of an inch and even some closer to 3/8 of an inch (0.375″)! However, while this may change slightly barrel to barrel, most recently Scott has been jumping around 0.120”.

While you might find good precision beyond 0.120”, longer jumps may require additional chamber freebore, meaning a gunsmith needs to modify your chamber to be able to jump that far. With traditional chambers, jumping 0.120” or more may require you to seat the bullet too far in the case. Scott says that he never wants the bearing surface of the bullet to be below the neck/shoulder junction on the case. That helps you stay away from the base of the neck where the “dreaded donut” could lead to shot-to-shot inconsistencies (more on the donut). Also, seating bullets further out allows more volume in the case which can actually allow you to achieve faster muzzle velocities without increasing pressure. (Read Bryan Litz explaining more about this.)

Keeping Bullet Bearing Surface Above Neck Shoulder Junction In Case

Scott Satterlee says when he is testing jump, he doesn’t do anything too drastically different than what the Berger Bullets Reloading Manual recommends (read that here), except he usually tests with jumps at 0.030”, 0.050”, 0.080”, 0.100” and 0.120”, rather than the intervals Berger suggests. Scott said sometimes he may just start at 0.050″. After he figured out which one groups best (as explained in the prior section), he then tests jumps a little below that and maybe 0.010-0.020” above it to make sure it continues to group well. That is how he makes sure that is a “durable” jump.

By the way, I do want to point out that Berger Bullets is the only reloading manual or published book I’ve found that actually recommends testing bullet jumps out to 0.100” off the lands or more. As we saw in the first article in this series, virtually everyone recommends jumping 0.020” or less for the best precision. Berger is the one outlier I’ve come across, but this research seems to confirm that they have been giving us good advice. Thanks, Berger!

I’ll try to side-step the debate of how many rounds you need to fire at each bullet jump for your results to be “conclusive” from a statistical perspective. There has been a lot of debate on that topic in the comments of this series of posts. There seems to be a purist/mathematical view which leads to very large sample sizes, and a practical/pragmatic view that says you can do it with one 5 shot group. I’ll leave it up to you guys to decide where you fall. Simply put, the larger the sample size the more confidence you can have in the results.

Alternatively, you could do load development in a similar
fashion to Mark’s 20-shot jump test, testing from touching the lands out to
0.095” or even 0.120”. However, the statistician Mark had analyze the data did
say that testing in 0.005” increments didn’t seem necessary from a statistical
perspective, although having data in 0.005” increments helped as he did calculations
for p-tests to ensure
these results were statistically significant. His professional opinion was that
tests in 0.010” increments would have reached the same conclusions.

If you do want to use something more like Mark’s 20-shot jump test, you might consider running through it at least 3 times to confirm the patterns you are seeing persist. To conserve barrel life, you might consider starting at 0.040” or 0.050″ from the lands and test in 0.010” increments, as the statistician suggested. If you did those things you could test the following 9 jumps with 3 to 5 shots each, and then graph the vertical POI of your results and look for the flat spots: 0.040, 0.050, 0.060, 0.070, 0.080, 0.090, 0.100, 0.110, 0.120. For more details on Mark’s approach and what I mean by “flat spots,” read this post.

Adjust Your Parallax!

My last tip is when we’re doing these kinds of tests and making decisions based on relatively minor differences in group size or patterns in shot-to-shot POI, it is especially critical to ensure your parallax is adjusted properly. Even at 100 yards, you can have shot-to-shot variance from parallax, which just adds noise to your data and can result in false positives and bad decisions. Not sure how to adjust your parallax? Watch this video

Shortcuts To Loads & Components

While some people love to tinker with load development, there are others that simply want to find a load in the shortest number of steps possible. For the latter group, I want to mention a couple of resources that could be potential shortcuts for finding a good powder charge or combination of components to use.

  • What The Pros Use: Load Data. This series of articles shows what components and specific powder weights the top-ranked precision rifle competitors in the country are running in their match ammo.
  • My Complete Load Data: This is the page I use to keep track of all my load data, for cartridges like 6mm Creedmoor, 6XC, 6.5 Creedmoor, 7mm Rem Mag, 300 Norma Mag, 338 Lapua Mag, 375 CheyTac, and more. It is actually what I use to reference my own load data, so it’s always kept up-to-date.

The Point of Diminishing Returns: How Much Does It Matter?

Finally, there are a couple timely reminders we should keep in mind. If you enjoy tinkering, then I don’t want to pour cold water on you. But there is definitely a point of diminishing returns when it comes to load development. For example, reducing your group size from 0.5 MOA to 0.1 MOA may only increase your hit probability at long range by 1-2%. That isn’t just my opinion, but is based on hard data you can see on the chart below and read more about here: How Much Does Group Size Matter?

How Much Do Smaller Groups Matter

Shrinking your muzzle velocity’s standard deviation from 10 fps to 3 fps may only increase your hit probability at long range by 1-2%. You can see that in the chart below and read more about that here: How Much Does SD Matter?

Effect of Muzzle Velocity SD on Hit Probability

As always, it depends on the size of the target and other factors. However, if you aren’t shooting extremely tiny targets or Extreme Long Range (ELR), and you aren’t competing at the absolute highest levels (i.e. you aren’t one of the top 25 shooters in the country) – tuning your load to the Nth degree may not matter as much as you think. Hopefully, those stats help us put into context that point of diminishing returns.

I wrote an entire series of articles called “How
Much Does It Matter?
” that took an objective approach to those factors,
as well as many others. If you have not ever read that, I would highly
recommend it! I promise you’ll learn something, and probably find a few
surprises. I know I did!

Series Wrap-Up!

I hope you guys enjoyed this series of articles on bullet
jump as much as I did! I know it challenged a lot of things I had simply been
assuming were the unquestionable truth in the past. Even if you’re a still a skeptic,
I’d challenge you to go try it for themselves. That is exactly what I plan to do!

And to Mark Gordon – Thank you for being willing to share
your hard work with the rest of us! I know you could have kept all this data
private and thought of it as a competitive advantage for Short Action Customs,
but we appreciate your openness. We all got to learn something from it, and this
is a huge contribution to the shooting community! It also clearly shows the
methodical approach and extreme lengths you go to at SAC to ensure the rifles
and products you make are performing at the highest levels. Lots of people
think about doing stuff like this, but very, very few execute on that and see
it all the way through. Thank you for your passion and extreme internal drive
for excellence!

I’ll end with this quote, which seems fitting for this topic
and Mark’s research:

“It is easy to sit about the fireside or under the shade of the home trees, after a day’s work at competitive rifle practice, and talk over the causes of bad shots, and it’s good fellowship’s pleasures are not to be denied; but it’s not so easy to prove by repeated and, maybe, costly experiments that our fine theories are correct”. – Franklin Mann, The Bullet’s Flight From Powder To Target (Published 1909)

Here are links to all the articles in this series:

  1. Bullet Jump & Seating Depth: Best Practices & Conventional Wisdom
  2. How Fast Does A Barrel Erode?
  3. Bullet Jump: Is Less Always Better?
  4. More Bullet Jump Research!
  5. Mark’s 18-Shot Bullet Jump Challenge!
  6. Bullet Jump Research: Executive Summary & Load Development Tips
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