What is “Overbore”? That’s a question rifle shooters can debate to no end. This article from our archives proposes one way to identify “overbore cartridges”. We think the approach outlined here is quite useful, but we know that there are other ways to define cartridges with “overbore” properties. Whenever we run this article, it stimulates a healthy debate among our readers — and that is probably a good thing.
Forum Member John L. has been intrigued by the question of “overbore” cartridges. People generally agree that overbore designs can be “barrel burners”, but is there a way to predict barrel life based on how radically a case is “overbore”? John notes that there is no generally accepted definition of “overbore”. Based on analyses of a wide variety of cartridges, John hoped to create a comparative index to determine whether a cartridge is more or less “overbore”. This, in turn, might help us predict barrel life and maybe even predict the cartridge’s accuracy potential.
John tells us: “I have read countless discussions about overbore cartridges for years. There seemed to be some widely accepted, general rules of thumb as to what makes a case ‘overbore’. In the simplest terms, a very big case pushing a relatively small diameter bullet is acknowledged as the classic overbore design. But it’s not just large powder capacity that creates an overbore situation — it is the relationship between powder capacity and barrel bore diameter. Looking at those two factors, we can express the ‘Overbore Index’ as a mathematical formula — the case capacity in grains of water divided by the area (in square inches) of the bore cross-section. This gives us an Index which lets us compare various cartridge designs.”
OVERBORE INDEX Chart
So what do these numbers mean? John says: “My own conclusion from much reading and analysis is that cartridges with case volume to bore area ratio less than 900 are most likely easy on barrels and those greater than 1000 are hard on barrels.” John acknowledges, however, that these numbers are just for comparison purposes. One can’t simply use the Index number, by itself, to predict barrel life. For example, one cannot conclude that a 600 Index number cartridge will necessarily give twice the barrel life of a 1200 Index cartridge. However, John says, a lower index number “seems to be a good predictor of barrel life”.
John’s system, while not perfect, does give us a benchmark to compare various cartridge designs. If, for example, you’re trying to decide between a 6.5-284 and a 260 Remington, it makes sense to compare the “Overbore Index” number for both cartridges. Then, of course, you have to consider other factors such as powder type, pressure, velocity, bullet weight, and barrel hardness.
Overbore Cases and Accuracy
Barrel life may not be the only thing predicted by the ratio of powder capacity to bore cross-section area. John thinks that if we look at our most accurate cartridges, such as the 6 PPC, and 30 BR, there’s some indication that lower Index numbers are associated with greater inherent accuracy. This is only a theory. John notes: “While I do not have the facilities to validate the hypothesis that the case capacity to bore area ratio is a good predictor of accuracy — along with other well-known factors — it seems to be one important factor.”
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Nosler has introduced a new 6.5mm (.264 caliber) hunting cartridge, the 26 Nosler. Nosler will initially offer 26 Nosler cartridge brass, and then, eventually, 26 Nosler loaded ammunition.
This new cartridge is designed to be a speedy, flat-shooting hunting cartridge, with performance exceeding a 6.5-284. This is possible because the 26 Nosler is a big, long cartridge with plenty of “boiler room”. Length from base to neck/shoulder junction is 2.33″ for the 26 Nosler, compared to 1.91″ for the 6.5-284 (and 2.04″ for a 7mm Rem Magnum). The 26 Nosler has a 35° shoulder angle and a magnum-size 0.534″ outside rim diameter.
The 26 Nosler cartridge can drive the Nosler 129 grain, AccuBond® LR bullet at 3400 fps. Zeroed at 350 yards, the 26 Nosler has a Point Blank Range of 0-415 yards. Loaded with the 129gr Accubond, the 26 Nosler retains as much velocity at 400 yards as a .260 Rem produces at the muzzle. This makes the 26 Nosler a “quintessential deer, antelope and long-range” cartridge according to company CEO/President Bob Nosler.
Content of all kinds is going digital, and that includes Reloading manuals. Now Hornady is offering an eBook version of the Hornady Handbook of Cartridge Reloading (9th Edition). Priced at $18.99, the eBook version of the Hornady Reloading Manual is now available for iOS (Apple) devices, for Android devices, and for Kindle eReaders.
For Apple products such iPads and iPhones etc., you can source Hornady’s manual from the iTunes iBook store. For Android tablets and Kindle readers, you can get the Kindle edition from Amazon.com. (NOTE: Android users must install a free Kindle App.)
Hornady’s latest Handbook of Cartridge Reloading features over 900 pages of information, including much new data for the 9th Edition. For many cartridge types, load recipes for new propellants such as Power Pro Varmint, AR-Comp, and CFE-223 have been added in the 9th Edition. Cartridge additions include the 17 Hornet, .327 Federal, .356 Winchester, .416 Barrett and .505 Gibbs. You’ll also find expanded data on over 20 favorite cartridges including: .223 Rem, 300 Whisper/AAC Blackout, .308 Win, .25-06, .257 Wby Mag, and many more. And of course the load recipes provide cover popular Hornady bullets V-MAX, SST, InterBond, InterLock, A-MAX, XTP, NTX and more. Each cartridge write-up features applicable Hornady bullets along with velocity/powder charts for quick and easy reference.
In addition to the comprehensive reloading charts, this reference manual provides helpful explanations of internal, external and terminal ballistics. To learn more about the eBook versions of Hornady’s latest Reloading manual, visit iTunes or Amazon.com.
eBook Tip from EdLongrange. We welcome reader submissions.
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On his Riflemans’ Journal blog, German Salazar wrote an excellent article about cartridge Case-Head Separation. We strongly recommend that you read this article. German examines the causes of this serious problem and he explains the ways you can inspect your brass to minimize the risk of a case-head separation. As cases get fired multiple times and then resized during reloading, the cases can stretch. Typically, there is a point in the lower section of the case where the case-walls thin out. This is your “danger zone” and you need to watch for tell-tale signs of weakening.
The photo below shows a case sectioned so that you can see where the case wall becomes thinner near the web. German scribed a little arrow into the soot inside the case pointing to the thinned area. This case hadn’t split yet, but it most likely would do so after one or two more firings.
One great tip offered by German Salazar involves using a bent paper clip to detect potential case wall problems. Slide the paper clip inside your case to check for thin spots. German explains: “This simple little tool (bent paper clip) will let you check the inside of cases before you reload them. The thin spot will be immediately apparent as you run the clip up the inside of the case. If you’re seeing a shiny line on the outside and the clip is really hitting a thin spot inside, it’s time to retire the case. If you do this every time you reload, on at least 15% of your cases, you’ll develop a good feel for what the thin spot feels like and how it gets worse as the case is reloaded more times. And if you’re loading the night before a match and feel pressured for time — don’t skip this step!”
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Since 2010, Lapua has shipped its quality cartridge brass in sturdy blue plastic boxes. Here’s a handy tip for you — don’t toss the plastic boxes when you load up your brass! These are double-duty containers. If you’re not familiar with “Blue Box” Lapua brass, you may not realize that the boxes are designed to serve as 50-round carriers for your loaded ammo and fired cases. (Yes we know some folks who’ve been tossing out their blue boxes without knowing how the boxes work as caddies.)
Snapped in place under the box lid is a rectangular plastic grid that fits in the bottom of the box. Pop the grid loose and slide it into the box with the smooth side facing up. Side supports molded into the lower section hold the grid in place.
Voilà, instant Ammo Box! Each grid contains holes for fifty (50) loaded rounds or empty cases. The convertible plastic container/ammo box is a great idea that Lapua executed very nicely. Now you have even more motivation to purchase your cartridge brass from Lapua.
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Lapua just dropped a bombshell — multiple bombshells, in fact. Lapua just announced that it will be producing .221 Fireball brass and .50 BMG brass starting early 2014. This will be the first truly match-grade brass ever offered for the .221 Fireball. That’s great news for varminters, who can use Lapua’s new .221 Fireball brass “as is” or neck it down to .20 Vartarg or 17 Fireball. Tactical shooters can also use the .221 Fireball brass to make the .300 Whisper and 300 Blackout sub-sonic cartridges. At the other end of the spectrum, ultra-long-range shooters now have a new ultra-premium brass source for the mighty .50 BMG. This is potentially a “game-changer” for fifty-cal shooters who have had to “make do” with military surplus brass for the most part. Lapua says the new brass, both .50 BMG and .221 Fireball, should be in the USA by early April, 2014. Sorry, no pricing info is yet available.
Here is the Lapua Product Announcement for .221 Fireball and .50 BMG Brass:
New 180-Grain and 150-Grain 7mm Scenar-L Bullets
The other big news from Lapua is the release of two new 7mm (.284 caliber) Scenar-L target bullets. Recognizing the popularity of 7mm cartridges among F-Class Open Division shooters, Lapua will offer a high-BC, 180-grain bullet. As part of the “L” series, this new 180-grainer bullet should exhibit extreme consistency in base-to-ogive measurements and bullet weight. We expect this new 180gr projectile to be extremely accurate in the .284 Winchester, .284 Shehane, 7mm WSM, and 7mm RSAUM — popular chamberings for F-Class and long-range benchrest shooters. No BC information has been released yet, but we expect the BC number to be quite high, giving this bullet great wind-bucking capability. In addition to the new 180gr 7mm Scenar-L, Lapua will offer a new 150gr 7mm bullet. This is optimized for medium range competition in Silhouette and Across-the-Course competition. It should offer great accuracy, but with less felt recoil than its 180-grain bigger brother.
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We can predict, with some certainty, how long a light bulb will last (in use), or a shingle roof, or even a nuclear reactor. But how about barrels? Is there a way to reliably estimate barrel life based on known characteristics? This article explains one effort to quantify barrel life…
How long will a barrel last before the accuracy “goes south”? There are so many variables involved (powder type, bore diameter, bullet coatings etc.) that it’s hard to predict. You might say “Well, my buddy has a .243 and he got 1500 rounds before the throat was shot out” — those kind of comparisons can be useful, but they’re not very scientific, and they won’t help much if you’ve got a gun in a new chambering (such as the 6.5×47) for which long-term test results are lacking.
Is there a more reliable way to predict barrel life — one that will work for a broad range of calibers? Well, Forum member MikeCr has developed an Excel spreadsheet that accounts for a number of variables, and gives a pretty good estimate of useful barrel life, whether you’re shooting a .223 Rem or a 338 Lapua Magnum. Mike’s program predicts barrel life using five variables: 1) Bullet Diameter; 2) Powder Charge weight; 3) Powder Heat Potential (KJ/kg); 4) Pressure (in psi); and 5) Bullet Coating (yes/no). Mike provides a table with Heat Potential ratings for most popular powder types. The user needs to know the pressure of his load. This can be estimated with QuickLOAD.
You can download the lastest version of Mike’s spreadsheet below. You’ll need Excel or an Excel viewer to open the file.
Shown below is Mike’s Spreadsheet, with variables for a 6BR shooting 105gr “naked” bullets with 30.3 grains of Hodgdon Varget powder. The formula predicts 2401 rounds of barrel life. That corresponds pretty well to what we’d expect for a 6BR — about 2500 rounds.
Mike observes: “There has been alot of discussion lately related to cartridge design and resulting barrel life. This is a really important factor to consider amongst a myriad of choices. Barrel life is controversial, and subjective. There are no clear-cut standards for comparison. But a few years ago, I put together a spreadsheet based on Bart Bobbit’s rule of thumb. It worked pretty good, only occasionally failing some tests when validated against posted barrel lives.
According to Ken Howell, I had to account for pressure. And Henry Child’s powder temperature testing provided another piece needed. So, I’ve tweaked it here and there to pass more tests. From 223rem to 300 UltraMagnum. Another element added, but turned off is shot interval. I would need way more tests to lock in on this. But everyone knows, the faster you shoot, the worse the barrel life.
Anyway, another factor hard to define is ‘accurate’ barrel life. This cannot be quantified without standards. Barrels are replaced when expectations are no longer met. I feel that a [barrel] passes peak potential in a finite period due to throat erosion. But that don’t mean it’s toast, if it still shoots well enough. It’s just as likely that many of us never see that peak potential anyway. It’s a slippery thing. Point-blank BR competitors will toss a barrel when it leaves the 1s. I could get another 4000 rounds from it, and be content with its performance, I’m sure.”
NOTE: Mike says: “This spreadsheet may show a lower barrel life than you prefer. But it pretty well spotlights cartridges to stay away from if you plan much time at the range or in dog town.”
Editor’s Comment: We want to stress that Mike’s spreadsheet is a helpful tool, but it is not a definitive “take-it-to-the-bank” indicator of barrel life. Mike cautions that predicting barrel life involves so many different factors (including how hot the barrel is run), that the task is a bit like predicting tread life on car tires. Still, the spreadsheet is very helpful. It can certainly warn us that some chamberings (such as the 6-284) are likely to be barrel burners. That can help you make a smart decision when choosing a chambering for your next rifle.
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Forum Member John L. has been intrigued by the question of “overbore” cartridges. People generally agree that overbore designs can be “barrel burners”, but is there a way to predict barrel life based on how radically a case is “overbore”? John notes that there is no generally accepted definition of “overbore”. Based on analyses of a wide variety of cartridges, John hoped to create a comparative index to determine whether a cartridge is more or less “overbore”. This, in turn, might help us predict barrel life and maybe even predict the cartridge’s accuracy potential.
John tells us: “I have read countless discussions about overbore cartridges for years. There seemed to be some widely accepted, general rules of thumb as to what makes a case ‘overbore’. In the simplest terms, a very big case pushing a relatively small diameter bullet is acknowledged as the classic overbore design. But it’s not just large powder capacity that creates an overbore situation — it is the relationship between powder capacity and barrel bore diameter. Looking at those two factors, we can express the ‘Overbore Index’ as a mathematical formula — the case capacity in grains of water divided by the area (in square inches) of the bore cross-section. This gives us an Index which lets us compare various cartridge designs.”
OVERBORE INDEX Chart
So what do these numbers mean? John says: “My own conclusion from much reading and analysis is that cartridges with case volume to bore area ratio less than 900 are most likely easy on barrels and those greater than 1000 are hard on barrels.” John acknowledges, however, that these numbers are just for comparison purposes. One can’t simply use the Index number, by itself, to predict barrel life. For example, one cannot conclude that a 600 Index number cartridge will necessarily give twice the barrel life of a 1200 Index cartridge. However, John says, a lower index number “seems to be a good predictor of barrel life”.
John’s system, while not perfect, does give us a benchmark to compare various cartridge designs. If, for example, you’re trying to decide between a 6.5-284 and a 260 Remington, it makes sense to compare the “Overbore Index” number for both cartridges. Then, of course, you have to consider other factors such as powder type, pressure, velocity, bullet weight, and barrel hardness.
Overbore Cases and Accuracy
Barrel life may not be the only thing predicted by the ratio of powder capacity to bore cross-section area. John thinks that if we look at our most accurate cartridges, such as the 6 PPC, and 30 BR, there’s some indication that lower Index numbers are associated with greater inherent accuracy. This is only a theory. John notes: “While I do not have the facilities to validate the hypothesis that the case capacity to bore area ratio is a good predictor of accuracy — along with other well-known factors — it seems to be one important factor.”
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We had a chance to try out the new power case trimmer head from Little Crow Gunworks. Dubbed the “World’s Finest Trimmer” (WFT) by its inventor, Dale Hegstrom, this device proved fast, precise, and easy to use. When compared to a Hornady Lock ‘N Load hand-crank trimmer, the WFT processed cases twice as fast, and delivered a more uniform cut length with our test brass.
The WFT features a steel shell-holder, aluminum body, and steel drive shank. You can chuck it into any electric drill or power device that can handle the 3/8″ shank. Unlike most case trimming tools, the WFT indexes off the shoulder datum. This permits you to trim cases very quickly, without fiddling around with rim-grabbing collets, or shell-holders. Watch the videos to see the WFT in action.
WFT is Fast and User-Friendly
Mark LaFevers, our tester, was easily able to trim five (5) cases in under 30 seconds. It took quite a bit longer to trim five cases with the Hornady trimmer he used for comparison. Mark noted that, after just a 20 or so manually-trimmed cases, his arm would start to fatigue. By contrast, he could effortlessly trim 100 or more cases with the WFT. For older folks with a bit of arthritis, the WFT makes life easier. Mark observed that the WFT produces a “nice, square, clean cut”, while offering a “very fast cycle rate”. He tells us, “once you get the hang of it, you probably can trim your brass two, if not three times as fast.”
Mark really liked the WFT tool, and a WFT will be replacing his hand trimmer for big jobs. One downside is that, currently, the WFT is cartridge specific — you normally need to have a different tool for each cartridge type you trim. And there are no swappable inserts allowing you to trim different cartridge types with the same tool. However some WFT versions WILL trim different cartridge types within the same “family”, such as .270 Win and .30-06.*
Hi-Rez Video Shows “Trim-Off” Challenge between WFT and Hornady Trimmer
You should definitely watch the five-minute video below. Mark trims five cases with the WFT, and then five more with the Hornady tool. He times the operation of each device and then measures the trimmed cases. The total variation (in length) of the WFT-trimmed cases was .001. With the Hornady tool, there was a much larger spread: .007″ (seven thousandths). Mark cautioned: “Normally the Hornady tool does a bit better than this — the variance won’t be so large. But getting better results (with the Hornady) might require trimming, measuring, then trimming again. In the video I was trying to move pretty quickly and the measurements were all taken after the initial trim. Possibly, if I slowed down when using the Hornady trimmer, the OAL measurements would have been more consistent. But that just further reinforces the point that the WFT is faster.”
NOTE: If you have a fast connection, we suggest you select 720p (HiRez) and expand to full screen.
In the video below, WFT creator Dale Hegstrom demos his device and shows how quickly it can trim a large quantity of brass. Note how the WFT is attached to a common rechargeable power drill.
“World’s Finest Trimmer” Costs $69.95
The Little Crow Gunworks “World’s Finest Trimmer is available for $69.95 from various vendors including Creedmoor Sports. WFTs index off the shoulder, not the base. The case fits tightly into a steel bearing which has been machined to a specific caliber. This decouples the stationary case from the spinning cutting blade and body, giving you a smooth, exact cut each time. While the WFT makes a nice, square cut, we do recommend chamfering inside and outside after the brass is trimmed to length.
*Most WFTs are cartridge specific. Available sizes include: .204 Ruger, .223 Rem, 22-250, 6mmBR, 6.5 Grendel, 6.5×47 Lapua, 6.5 Creedmoor, 6.5-284 (and 6mm-284), 6.8 SPC, 270 WSM, 7mm Rem Mag (and 300 Win Mag), .308 Win, 300 WSM, .338 Lapua Magnum. There is a ‘5 in 1′ WFT unit that will handle .17 Rem, .221 Fireball, .222, .223 Rem, and .222 Mag. The 6mmRem unit also works with .257 Roberts and 7×57 Mauser. The .30-06 WFT will trim .270 Win, .280 Rem, and .25-06 as well. And the WFT for Ultramags works with 7mm, 300, and .338 Ultramags.
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In our Shooters’ Forum a reader recently asked: “How much neck tension should I use?” This prompted a Forum discussion in which other Forum members recommended a specific number based on their experience, such as .001″, .002″, or .003″. These numbers, as commonly used, correspond to the difference between case-neck OD after sizing and the neck OD of a loaded round, with bullet in place. In other words, the numbers refer to the nominal amount of interference fit (after sizing).
While these commonly-used “tension numbers” (of .001″, .002″ etc.) can be useful as starting points, neck tension is actually a fairly complex subject. The actual amount of “grip” on the bullet is a function of many factors, of which neck-OD reduction during sizing is just one. Understanding these many factors will help you maintain consistent neck tension as your brass “evolves” over the course of multiple reloadings.
Neck Tension (i.e. Grip on Bullets) Is a Complex Phenomenon
While we certainly have considerable control over neck tension by using tighter or looser bushings (with smaller or bigger Inside Diameters), bushing size is only one factor at work. It’s important to understand the multiple factors that can increase or decrease the resistance to bullet release. Think in terms of overall brass-on-bullet “grip” instead of just bushing size.
One needs to understand that bushing size isn’t the beginning and end of neck tension questions, because, even if bushing size is held constant, the amount of bullet “grip” can change dramatically as the condition of your brass changes. Bullet “grip” can also change if you alter your seating depth significantly, and it can even change if you ultrasonically clean your cases.
Bullet grip is affected by many things, such as:
1. Neck-wall thickness.
2. Amount of bearing surface (shank) in the neck.
3. Surface condition inside of neck (residual carbon can act as a lubricant; ultrasonic cleaning makes necks “grabby”).
4. Length of neck (e.g. 6BR neck vs. 6BRX).
5. Whether or not the bullets have an anti-friction coating.
6. The springiness of the brass (which is related to degree of work-hardening; number of firings etc.)
7. The bullet jacket material.
8. The outside diameter of the bullet and whether it has a pressure ridge.
9. The time duration between bullet seating and actual firing (necks can stiffen with time).
10. How often the brass is annealed
— and there are others…
Seating Depth Changes Can Increase or Decrease Grip on Bullet
You can do this simple experiment. Seat a boat-tail bullet in your sized neck with .150″ of bearing surface (shank) in the neck. Now remove the bullet with an impact hammer. Next, take another identical bullet and seat it with .300″ of bearing surface in another sized case (same bushing size/same nominal tension). You’ll find the deeper-seated bullet is gripped much harder.
Neck-Wall Thickness is Important Too
I have also found that thinner necks, particularly the very thin necks used by many PPC shooters, require more sizing to give equivalent “grip”. Again, do your own experiment. Seat a bullet in a case turned to .008″ neckwall thickness and sized down .003″. Now compare that to a case with .014″ neckwall thickness and sized down .0015″. You may find that the bullet in the thin necks actually pulls out easier, though it supposedly has more “neck tension”, if one were to consider bushing size alone.
In practical terms, because thick necks are less elastic than very thin necks, when you turn necks you may need to run tighter bushings to maintain the same amount of actual grip on the bullets (as compared to no-turn brass). Consequently, I suspect the guys using .0015″ “tension” on no-turn brass may be a lot closer to the guys using .003″ “tension” on turned necks than either group may realize.
Toward a Better Definition of Neck Tension
As a convenient short-cut, we tend to describe neck tension by bushing size alone. When a guy says, “I run .002 neck tension”, that normally means he is using a die/bushing that sizes the necks .002″ smaller than a loaded round. Well we know something about his post-sizing neck OD, but do we really have a reliable idea about how much force is required to release his bullets? Maybe not… This use of the term “neck tension” when we are really only describing the amount of neck diameter reduction with a die/bushing is really kind of incomplete.
My point here is that it is overly simplistic to ask, “should I load with .001 tension or .003?” In reality, an .001″ reduction (after springback) on a thick neck might provide MORE “grip” on a deep-seated bullet than an .003″ reduction on a very thin-walled neck holding a bullet with minimal bearing surface in the neck. Bushing ID is something we can easily measure and verify. We use bushing size as a descriptor of neck tension because it is convenient and because the other important factors are hard to quantify. But those factors shouldn’t be ignored if you want to maintain consistent neck tension for optimal accuracy.
Consistency and accuracy — that’s really what this all about isn’t it? We want to find the best neck tension for accuracy, and then maintain that amount of grip-on-bullet over time. To do that you need to look not only at your bushing size, but also at how your brass has changed (work-hardened) with time, and whether other variables (such as the amount of carbon in the neck) have changed. Ultimately, optimal neck tension must be ascertained experimentally. You have to go out and test empirically to see what works, in YOUR rifle, with YOUR bullets and YOUR brass. And you may have to change the nominal tension setting (i.e. bushing size) as your brass work-hardens or IF YOU CHANGE SEATING DEPTHS.
Remember that bushing size alone does not tell us all we need to know about the neck’s true “holding power” on a bullet, or the energy required for bullet release. True bullet grip is a more complicated phenomenon, one that is affected by numerous factors, some of which are very hard to quantify.
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On his Riflemans’ Journal blog, German Salazar wrote an excellent article about cartridge Case-Head Separation. We strongly recommend that you read this article. German examines the causes of this serious problem and he explains the ways you can inspect your brass to minimize the risk of a case-head separation. As cases get fired multiple times and then resized during reloading, the cases can stretch. Typically, there is a point in the lower section of the case where the case-walls thin out. This is your “danger zone” and you need to watch for tell-tale signs of weakening.
The photo below shows a case sectioned so that you can see where the case wall becomes thinner near the web. German scribed a little arrow into the soot inside the case pointing to the thinned area. This case hadn’t split yet, but it most likely would do so after one or two more firings.
One great tip offered by German Salazar involves using a bent paper clip to detect potential case wall problems. Slide the paper clip inside your case to check for thin spots. German explains: “This simple little tool (bent paper clip) will let you check the inside of cases before you reload them. The thin spot will be immediately apparent as you run the clip up the inside of the case. If you’re seeing a shiny line on the outside and the clip is really hitting a thin spot inside, it’s time to retire the case. If you do this every time you reload, on at least 15% of your cases, you’ll develop a good feel for what the thin spot feels like and how it gets worse as the case is reloaded more times. And if you’re loading the night before a match and feel pressured for time — don’t skip this step!”
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One of our Shooters’ Forum readers, Trent from Louisiana, asked for help deciding between a 260 Remington and a 6.5×55 for his latest gun project. In the Forum thread, respected UK gun writer Laurie Holland provided a good summary of the differences between the two chamberings. Laurie writes:
“The 6.5×55 case has 6 or 7% more capacity than the .260s, even more in practice when both are loaded to standard COALs with heavy bullets, which sees them having to seated very deep in the .260 Rem using up quite a lot of powder capacity. So loaded up for reasonable pressures in modern actions, the 6.5×55 will give a bit more performance.
The issue for many is what action length is available or wanted, the 6.5 requiring a long action. So sniper rifle / tactical rifle competitors will go for the .260 Rem with the option of the many good short-bolt-throw designs around with detachable box magazines. If a bit more performance is needed, the .260AI gives another 100-150 fps depending on bullet weight.
Brass-wise, you’ve got really good Lapua 6.5×55 off the shelf that needs minimum preparation, and it’s strong and long-lived. There is an Ackley version too that was popular in F-Class in Europe for a while that isn’t too far short of 6.5-284 performance. If you go for .260 Rem, the American brass isn’t as good but you can neck-up Lapua or Norma .243 Win and trim them (or neck-down .308 Win or 7mm-08). This has the downside that doing so usually creates a noticeable ‘doughnut’ at the case-shoulder junction, that may cause problems depending on how deep bullets are seated.
For purely target shooting, I think I’d go with 6.5×55 if I was making the choice again today for performance and brass-preparation reasons. In fact, I’ve considered going back to the gunsmith to have the barrel rechambered.
You want a multi-purpose rifle though and that makes things trickier depending on the bullet weight(s) you want to use. The [typical] 6.5×55 and 6.5-08 throats are really designed for 140s, so 90-120s make a long jump into the rifling. If you’re always going to use 130s and up, it’s less of an issue. If you want to use the lighter stuff, I’d say go for .260 Rem and discuss the reamer with the gunsmith to come up with as good a compromise as you can depending on the mix of shooting. 1:8.5″ twist is the norm and handles all the usual sporting and match bullets; you can go for a little slower twist if you won’t use the heavies.
Over here in the UK, in Scotland to be precise, we have a top sporting rifle builder (Callum Ferguson of Precision Rifle Services) who almost specializes in .260 Rem usually built on Borden actions. He throats the barrel ‘short’ so it’s suited to varmint bullets, but will still handle the 100gr Nosler Partition which he says is more than adequate for any British deer species including Scottish red stags.
Accuracy-wise, I don’t think there’s anything between them if everything else is equal. The 6.5 has a reputation for superlative accuracy, but that was high-quality Swedish military rifles and ammunition matched against often not-so-high-quality military stuff from elsewhere. Put the pair in custom rifles and use equally good brass and bullets and you’ll be hard pressed to tell them apart.” – Laurie Holland
After Laurie’s helpful comments, some other Forum members added their insights on the 260 Rem vs. 6.5×55 question:
“To me, the .260 Remington has no advantage over the 6.5×55 if one is going to use a long action. Likewise, the only advantage the .260 has in a modern rifle is it can be used in a short-action. There is more powder capacity in the 6.5×55 so you have the potential to get more velocity plus there is a lot of reloading data available to you for loading at lower velocity/pressure if you choose. The Lapua brass is great and Winchester brass is pretty good at low pressures. Having loaded a good bit for both, the 6.5×55 would always get the nod from me. To me, if someone wants to use a short-action, the 6.5×47 Lapua is even a better option than the .260 for a target rifle.” — Olympian
“There is just one small item that has been missing from this conversation — the 6.5×55 has a non standard rim diameter of .479″ vs. the standard .473″ of a .308 and all of its varients. Depending on your bolt this may be an issue, or it may not.” — Neil L.
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How long will a barrel last before the accuracy “goes south”? There are so many variables involved (powder type, bore diameter, bullet coatings etc.) that it’s hard to predict. You might say “Well, my buddy has a .243 and he got 1500 rounds before the throat was shot out” — those kind of comparisons can be useful, but they’re not very scientific, and they won’t help much if you’ve got a gun in a new chambering (such as the 6.5×47) for which long-term test results are lacking.
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Neck-Wall Thickness is Important Too
“The 6.5×55 case has 6 or 7% more capacity than the .260s, even more in practice when both are loaded to standard COALs with heavy bullets, which sees them having to seated very deep in the .260 Rem using up quite a lot of powder capacity. So loaded up for reasonable pressures in modern actions, the 6.5×55 will give a bit more performance.
After Laurie’s helpful comments, some other Forum members added their insights on the 260 Rem vs. 6.5×55 question:
