The Myth of the Special Barrel and Ammo Match

[grauhanen]

Note: This will be about ten posts in length. It's a more abridged version of the model.

The Myth of the Special Barrel and Ammo Match: Why Your Rifle doesn't have a Soulmate​

The myth is taught to shooters and they believe it

When newer shooters look for advice about how improve results, they are given the same advice that they heard, advice that’s given at ranges, repeated on rimfire forums, and seems solid and reliable.

The advice says every rifle is different, unique. The shooter has to find the match ammo lot his rifle “likes” best. What shoots well in one rifle may not in another. It’s the match that counts. Every rifle has a soulmate. Find the right lot for the specific rifle and the honeymoon can begin. (In turn, it means every lot has a soulmate too.)

This sounds like special, high-level knowledge, perhaps even a little romantic. But from a very basic engineering and math perspective, it is incorrect. It’s a myth.

To understand why, let’s stop looking at different target results for a moment and look at how .22LR ammo and barrels are made and what manufacturers are aiming for.

 

[grauhanen]

The Ammo

Ammo Quality is Intrinsic, Built-in. It’s not a Match Made at the Range.

When match ammo manufacturing engineers make their products, they are not aiming to make ammo that matches any rifle model or particular rifle. That would be a haphazard, unplanned, unintentional. The only thing they can do is to make .22LR match ammo that is as uniform as possible. The goal is ammo uniformity. Uniformity helps give more similar trajectories.

The match ammo factory’s key goal is the elimination of differences between rounds in a lot. The engineers and technicians want every round to be a flawless duplicate. The problem, of course, is that this isn’t possible. Every lot is imperfect and flawed by variation between rounds. Some lots have less, others more.

 

[grauhanen]

Variation in ammo components

The ammo engineers and technicians are in a constant battle with constantly changing variables such as the exact amount and distribution of priming compound in the rim, the way the gunpowder burns, the thickness of the brass casing. The bullets alone can vary in areas including weight, diameter, shape, balance, heel symmetry.

A .22LR round can vary in multiple places at once. Less variation means smaller groups, more means larger ones.

Some of these areas of potential variation are, of course, more important than others, but the point is that all match ammo has variation, even the top tier flavors like X-Act, Midas, Tenex, and R50. Shooters expect top tier ammo to have less variation and they usually do. That's why they are top tier.

 

[grauhanen]

Variation in lot/round assembly

An additional problem facing the engineers is that the loading machines producing the lots are themselves changing during a production run. A production run typically produces many lots of various grades at a time. Despite attention from technicians, tooling wears down and change microscopically over time. As a result, the assembly of the components is not equally uniform through a production run.

The best lots are produced when the machinery is “dialed in” as much as possible and the components have little round to round variation. Poorer lots result when tooling is less perfect or nearing the end of it’s replacement cycle and the components have more round-to-round variation.

 

[grauhanen]

In match ammo making, the key point is uniformity. Uniformity is quality.

The less variation between rounds in a lot, the better the quality. The more variation between rounds in a lot, the poorer the quality. The match ammo makers goal is to produce the best ammo, the lots with less variation, not more. Less variation is always better. It’s better for all rifles.

It may help to think of ammo like fuel. High-quality, clean, premium fuel is objectively good. It will make a sports car run perfectly, and it will make a lawnmower run perfectly. Cheap gas with contaminants in it is objectively bad. It will make both engines sputter. The lawnmower can't "prefer" the dirtier gas and suddenly run better on it.

In the end, because factory machines wear by the hour and components vary, some lots come off the production line much closer to that perfect “clone” ideal than others. A good lot has fewer round-to-round differences; a poor lot has wide differences.

A consistent box of ammo is always better, no matter the rifle. A less inconsistent box of ammo is always poorer and will never perform like a more perfect box, no matter how much your barrel supposedly "likes" it.

 

[grauhanen]

The Barrel

Barrel quality is built-in. It’s not looking for a special match at the range.

Just like ammunition, rifle barrels operate on a straightforward scale of manufacturing quality. A good barrel is a good barrel. It doesn’t become a poor one because of the ammo. It doesn’t have a personality that searches for its soulmate ammo lot. It is a steel tube that can be ranked from excellent to poor based on how perfectly it was manufactured.

Every barrel maker is working off the same basic blueprint. The goal is essentially to produce barrels with as near perfect characteristics as possible. At the basic level these include a perfectly round, perfectly straight steel tunnel with consistent diameter that may taper uniformly to the muzzle, uniform rifling and surface finish, with a symmetrical, concentric crown.

But since no barrel material is perfect and no barrel-making machinery and work is perfect, bores are not equal. They vary in quality. Some are better (more perfect) than others. These barrels have fewer variations in the characteristics that matter. This means that they are more consistent. Other barrels have much less perfect bores which have more variation and are less consistent.

All imperfect barrels contribute variation (noise) to the results. Better barrels contribute less variation to results. They are more steady, more repeatable. Others introduce more variation to results.

The barrel doesn't take variation away. It can only add it. Whether it adds more or less isnthe result of bore quality. A good barrel adds less variation or noise, a poorer one adds more.

The bottom line about barrels: The barrel isn’t looking for a certain match, for a lot with the right mix of characteristics. It’s not like a guy looking for someone with the right mix of curves, the right hair color, the right clothes, the right legs. The barrel will shoot lots with good quality well – those with less round-to-round variation rather than more. If it could talk, it would say, “Just give me good quality ammo. Don’t think you should try to set me up with a special match.”

 

[grauhanen]

Heavy vs. Light Barrels (Stiffness and Vibration)

If ammo quality is built-in and barrel quality is built-in, why do different barrels look so different on the range? The answer is pure physics, specifically, barrel stiffness.

When a round is fired, it sends a wave down the steel, causing the barrel to vibrate like a tuning fork. How the barrel handles this depends entirely on its thickness:

• Heavier Barrels (High Stiffness): Thick profiles are rigid and heavy. They are hard to excite. They respond to ammo variation more calmly, more evenly. They are less sensitive to minor round-to-round variation. To use an analogy, they are like mature people who’ve seen it all before and don’t easily get excited by the little bumps in life.

• Lighter Barrels (Low Stiffness): Thin profiles are flexible and light. They are highly excitable and more sensitive. They react more strongly to round-to-round variation, magnifying even the smallest differences in the ammunition's speed. To return to the analogy, they are like young people who get easily upset by small bumps in life such as a “mean” social media comment.

When you run different lots of ammo through these two barrels, the results downrange are entirely predictable:

• With a Great Lot (Low Variation): The heavy barrel absorbs the minor differences calmly, producing tight, identical groups. The light barrel is so sensitive that it amplifies the tiny changes, producing groups that show noticeably more variation in size from group to group.

• With a Poor Lot (High Variation): The heavy barrel's mass still acts as a dampener, but the ammunition's internal inconsistencies force the groups to open up. The light barrel more completely gives in to the chaos, reacting more strongly to every fluctuation in pressure, resulting in more erratic, unpredictable groups.

The thin barrel doesn't "hate" the ammo, and the heavy barrel isn't "magical." The thin barrel is simply a highly sensitive instrument that more clearly reveals – magnifies – ammunition variation, while the heavy barrel has the physical mass to allow it to keep its composure when the ammo gets rough.

The bottom line: barrel diameter does not change which lot is better. Good ammo is good ammo.

When a lighter barrel gives many consecutive very small groups, it’s because the rounds it fired were very consistent, showing little variation from one round to the next. With those same rounds, a heavier barrel would have done even better.

 

[grauhanen]

The Sample Size Trap – A problem for every shooter

This is important and deserves attention.

Everyone hears this: “I shot the same match ammo in two good rifles and the results were different. One rifle did well and the other did not – with the same ammo. This means it’s true that rifles don’t like the same lots of ammo.”

That difference happens all the time. Two rifles, same ammo, different results.

The math shows that shooters are routinely fooled by sample sizes (the number of shots fired during a test).
Most serious shooters know that a single 5-shot group doesn't prove anything. They know a single “wallet” group means nothing.

To do a better test, these same shooters will take a box or two of a specific lot (50 to 100 rounds) and, in outdoor conditions, shoot ten separate 5-shot groups, average the sizes together, and then declare a winner.

They believe they have done a more rigorous test. But from a mathematical standpoint, this data is completely unreliable. The sample size is simply too small.

Imagine trying to evaluate music by listening to a 30-second snippet from random points of different Beethoven symphonies or Pink Floyd albums. A 30-second clip of a quiet section in a masterpiece might sound boring, while a 30-second clip of a mediocre song's best hook might sound brilliant. Too small a sample tells you nothing about the quality of the whole thing. It can easily mislead.

Think of testing an ammo lot like judging a baseball batter: you can’t reliably tell who’s a better hitter from the performance in a single game. A great .350 hitter can still strike out or ground out four times. A poor .175 hitter can get a home run in his first at-bat of the game. A false impression can be produced that doesn’t translate to an entire season.

The problem of small sample sizes explains why the same ammo gives different results in different rifles. It also explains why shooters may get different results on different days with the same rifle and ammo. (Sometimes called the Same Ammo Different Day problem).

 

[grauhanen]

Shooting outdoors with a lighter barrel is often not easy to evaluate

Shooting outdoors with a lightweight sporter rifle across random rests can be a recipe for unreliable testing results. This is more problematic without effective use of wind flags. And a lighter barrel is more sensitive than a heavier one, giving a wider range of results with all ammos.

Even without potential human error, there is a real danger of layering multiple sources of potential chaos or random chance. Fifty or 100 rounds is simply too small a snippet to be trustworthy.

When you average those ten 5-shot groups outdoors with a light barrel, you aren't simply averaging the ammo's performance. You are averaging a gust of wind, a shifting rest, shooter fatigue. You are also averaging good or bad luck if your groups are better or worse by chance. Good groups and bad groups are often only random acts of accuracy.

Averages and conclusions based on too small a sample are illusions that don’t reflect the true quality of a lot. But that’s what often happens at the range. It’s an almost inevitable result when the cost of ammo understandably limits extensive testing.

 

[grauhanen]

The Takeaways

Stop looking for your rifle's long-lost soulmate lot. A special ammo-rifle match doesn't exist.

The search is for ammo lots that are better quality than others.

• Lot quality drives results. Better lots have less variation between rounds, poorer lots have more.
• Barrels do not change lot quality. Good ammo is good ammo across barrels.
• Heavy barrels are calmer, less sensitive, than lighter ones. Lighter barrels are more sensitive making them amplify differences between rounds
• Testing samples that are too small are unreliable and misleading. They can tell you something not true.

 

[*lawrence]

How would this be definitively proved? I suspect, there are too many factors (barrel ~ new or used & length, ammo brand & lot variation, shooter ~ skill & health ~ at that moment, weather wind, rain, temperature plus many other factors) for this to be more than a theory that is very challenging to prove? But common sense would suggest it's a good theory.

 

[iron cat]

How would this be definitively proved? I suspect, there are too many factors (barrel ~ new or used & length, ammo brand & lot variation, shooter ~ skill & health ~ at that moment, weather wind, rain, temperature plus many other factors) for this to be more than a theory that is very challenging to prove? But common sense would suggest it's a good theory.

There has been some extensive testing done over the years indoors with various barrels and ammo.
I remember many years ago, if you sent your rifle to Rudy Schultz , he would set it up in a machine rest in the basement of his store and select which lot of Eley worked best in your rifle - on the premise that you would buy several 5000 lot cases from him.
That was in the 60's and 70's.
Cat

 

[tacoman]

When International Imports was in business in Waterloo On, he was the dealer for RWS, Lapua , Eley and had a 50 meter indoor test range and a machine rest , and you take or send you rifle there and he would test different ammo through it. I personally saw him try 5 different lots of RWS R50 through my Anschutz 1911 and the difference between lots was amazing . And saw this on other peoples rifles , with all the different brands , each barrel liked a certain lot much better than an other, but was not the same in another rifle. And if you couldn’t find a match, he didn’t even charge for the ammo he used, Rudy would just have you try on the next shipment , which was in the 80’s / 90’s when I was there. His daughter was on the Canadian National team and he had shot international himself , so he knew is stuff. I shot enough NRA small bore prone (NRA Master ) to be able to say there is a difference .The US Army Marksmanship unit in Ft Benning GA had a 100 M indoor test range just for matching lots of ammo to specific rifles. So, no it is not a myth .

 

[gorby]

Is there testing specific to rimfires to say that a lighter barrel of the same quality and same chamber is less accurate than a heavy one in a 5 shot group?