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January 5th, 2024
“The press is the heart of the handloading operation, also traditionally the most expensive single tool employed…” — Laurie Holland
British competitive shooter Laurie Holland has reviewed three popular, single-stage reloading presses for Target Shooter Magazine (targetshooter.co.uk). Laurie bolted up a Forster Co-Ax, RCBS Rock Chucker Supreme, and RCBS Summit to his reloading bench and put the three presses through their paces. These three machines are very different in design and operation. The venerable Rock Chucker is a classic heavy, cast-iron “O”- type press that offers lots of leverage for tough jobs. The smaller RCBS Summit press is an innovative “upside-down” design with a large center column and open front. It offers a small footprint and easy case access from the front. The Co-Ax is unique in many respects — dies slide in and out of the upper section which allows them to “float”. The cartridge case is held in the lower section by spring-loaded jaws rather than a conventional shell-holder.
If you are considering purchasing any one of these three presses, you should read Laurie’s article start to finish. He reviews the pros and cons of each press, after processing three different brands of brass on each machine. He discusses ergonomics, easy of use, press leverage, smoothness, priming function, and (most importantly), the ability to produce straight ammo with low run-out. The review includes interesting data on case-neck run-out (TIR) for RWS, Federal, and Norma 7x57mm brass.
 Review Quick Highlights:
RCBS Rock Chucker Supreme
“My expectations of the antediluvian RCBS Rock Chucker Supreme’s performance weren’t over high to be honest as I mounted it in the place of the Summit. As soon as I sized the first of the stretched RWS cases though, I saw why this press has been such a long-running favorite. The workload was considerably reduced compared to the other two presses and doing 40-odd cases took no time at all with little sweat — it just eats hard-to-size brass.”
RCBS Summit Press
“Despite its massive build and long-stroke operating handle, [the Summit] took more sweat than I’d expected, even if it was somewhat less work than with the Co-Ax. Although the Summit is apparently massive, I noticed that the die platform would tilt fractionally under the heaviest strains[.] It is nevertheless a very pleasant press in use and bullet seating was a doddle — the few examples tried proving very concentric on checking them afterwards. The optional short handle would be valuable for this task.”
Forster Co-Ax
“[On the Co-Ax], the operating handle is above the machine, located centrally [with] twin steel links at the top end of the press dropping down to the moving parts. The Co-Ax incorporates [many] novel features, principally its automatic and multi-case compatible shell-holder assembly with spring-loaded sliding jaws, very neat spent primer arrangements that allow hardly any gritty residues to escape and foul the moving parts and, the snap-in/out die fitment that allows rapid changes and lets the die ‘float’ in relation to the case giving very concentric results. I own this press and it meets my handloading needs very well.”
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March 14th, 2022
“The press is the heart of the handloading operation, also traditionally the most expensive single tool employed…” — Laurie Holland
British competitive shooter Laurie Holland has reviewed three popular, single-stage reloading presses for Target Shooter Magazine (targetshooter.co.uk). Laurie bolted up a Forster Co-Ax, RCBS Rock Chucker Supreme, and RCBS Summit to his reloading bench and put the three presses through their paces. These three machines are very different in design and operation. The venerable Rock Chucker is a classic heavy, cast-iron “O”- type press that offers lots of leverage for tough jobs. The smaller RCBS Summit press is an innovative “upside-down” design with a large center column and open front. It offers a small footprint and easy case access from the front. The Co-Ax is unique in many respects — dies slide in and out of the upper section which allows them to “float”. The cartridge case is held in the lower section by spring-loaded jaws rather than a conventional shell-holder.
If you are considering purchasing any one of these three presses, you should read Laurie’s article start to finish. He reviews the pros and cons of each press, after processing three different brands of brass on each machine. He discusses ergonomics, easy of use, press leverage, smoothness, priming function, and (most importantly), the ability to produce straight ammo with low run-out. The review includes interesting data on case-neck run-out (TIR) for RWS, Federal, and Norma 7x57mm brass.
 Review Quick Highlights:
RCBS Rock Chucker Supreme
“My expectations of the antediluvian RCBS Rock Chucker Supreme’s performance weren’t over high to be honest as I mounted it in the place of the Summit. As soon as I sized the first of the stretched RWS cases though, I saw why this press has been such a long-running favorite. The workload was considerably reduced compared to the other two presses and doing 40-odd cases took no time at all with little sweat — it just eats hard-to-size brass.”
RCBS Summit Press
“Despite its massive build and long-stroke operating handle, [the Summit] took more sweat than I’d expected, even if it was somewhat less work than with the Co-Ax. Although the Summit is apparently massive, I noticed that the die platform would tilt fractionally under the heaviest strains[.] It is nevertheless a very pleasant press in use and bullet seating was a doddle — the few examples tried proving very concentric on checking them afterwards. The optional short handle would be valuable for this task.”
Forster Co-Ax
“[On the Forster Co-Ax], the operating handle is above the machine, located centrally here [with] twin steel links at the top end of the press dropping down to the moving parts. The Co-Ax incorporates a number of novel features, principally its automatic and multi-case compatible shell-holder assembly with spring-loaded sliding jaws, very neat spent primer arrangements that allow hardly any gritty residues to escape and foul the moving parts and, the snap-in/out die fitment that allows rapid changes and also sees the die ‘float’ in relation to the case giving very concentric results. I own this press and it meets my handloading needs very well.”
Share the post "Reloading Press Comparison: Rock Chucker vs. Co-Ax vs. Summit"
April 15th, 2021
“The press is the heart of the handloading operation, also traditionally the most expensive single tool employed…” — Laurie Holland
British competitive shooter Laurie Holland has reviewed three popular, single-stage reloading presses for Target Shooter Magazine (targetshooter.co.uk). Laurie bolted up a Forster Co-Ax, RCBS Rock Chucker Supreme, and RCBS Summit to his reloading bench and put the three presses through their paces. These three machines are very different in design and operation. The venerable Rock Chucker is a classic heavy, cast-iron “O”- type press that offers lots of leverage for tough jobs. The smaller RCBS Summit press is an innovative “upside-down” design with a large center column and open front. It offers a small footprint and easy case access from the front. The Co-Ax is unique in many respects — dies slide in and out of the upper section which allows them to “float”. The cartridge case is held in the lower section by spring-loaded jaws rather than a conventional shell-holder.
If you are considering purchasing any one of these three presses, you should read Laurie’s article start to finish. He reviews the pros and cons of each press, after processing three different brands of brass on each machine. He discusses ergonomics, easy of use, press leverage, smoothness, priming function, and (most importantly), the ability to produce straight ammo with low run-out. The review includes interesting data on case-neck run-out (TIR) for RWS, Federal, and Norma 7x57mm brass.
Review Quick Highlights:
RCBS Rock Chucker Supreme
“My expectations of the antediluvian RCBS Rock Chucker Supreme’s performance weren’t over high to be honest as I mounted it in the place of the Summit. As soon as I sized the first of the stretched RWS cases though, I saw why this press has been such a long-running favorite. The workload was considerably reduced compared to the other two presses and doing 40-odd cases took no time at all with little sweat — it just eats hard-to-size brass.”
RCBS Summit Press
“Despite its massive build and long-stroke operating handle, [the Summit] took more sweat than I’d expected, even if it was somewhat less work than with the Co-Ax. Although the Summit is apparently massive, I noticed that the die platform would tilt fractionally under the heaviest strains[.] It is nevertheless a very pleasant press in use and bullet seating was a doddle — the few examples tried proving very concentric on checking them afterwards. The optional short handle would be valuable for this task.”
Forster Co-Ax
“[On the Co-Ax], the operating handle is above the machine, located centrally here [with] twin steel links at the top end of the press dropping down to the moving parts. The Co-Ax incorporates a number of novel features, principally its automatic and multi-case compatible shell-holder assembly with spring-loaded sliding jaws, very neat spent primer arrangements that allow hardly any gritty residues to escape and foul the moving parts and, the snap-in/out die fitment that allows rapid changes and also sees the die ‘float’ in relation to the case giving very concentric results. I own this press and it meets my handloading needs very well.”
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June 12th, 2019
In response to a Bulletin story about Norma powders at Midsouth Shooters Supply, one of our Forum members asked: “I’m having trouble finding Reloder 15 for my 6.5×47 Lapua — should I consider running Norma 203B instead?” As we’ve explained before, these two powders, both made by Bofors in Europe, are very, very similar. Here are some hard numbers that should demonstrate how virtually identical these powders really are.
Target Shooter Magazine writer Laurie Holland compared Norma 203B and Reloder 15 using data from QuickLOAD. Laurie also checked load manuals to see how listed charge weights varied for the two propellants. Laurie concluded there was very little difference between Norma 203B and Reloder 15.
 Norma 203B vs. Alliant Reloder 15
Commentary by Laurie Holland
Running [203B and RL15] through QuickLOAD doing a ‘charge table’ run for a 130gn Berger VLD at 2.700 COAL in 6.5X47 Lapua, gives very similar positions in the table [for both powders]. The charge required to achieve 62,000 psi estimated pressure varies by a mere 0.2 grains between the pair, Norma 203B being the heavier of the two. The estimated Muzzle Velocity (MV) also varies by a mere 2 fps, RL15 estimated to produce 2,946 fps MV compared to 2,944 fps for N203B at 62,000 psi (with the parameters I used).
If they aren’t the same thing, they’re so close as to make no difference and as Forum Boss points out, they’re made by the same people (Bofors) in the same plant.
[The Berger Reloading Manual includes data for both powders] for the .308 Winchester and heavier bullets (185 to 230 grains). Maximum charges and claimed MVs are not always identical, but are so close as to be marginally different production lots of the same thing, or maybe the result of minor testing variations.
.308 Win Max Charge Weights in Grains (RL15 / N203B) (Berger Manual)
MVs [for the four bullet types] are close but not identical, the largest difference being for the 210s which shows RL15 producing 2,428 fps MV v 2,383 for Norma 203B.
Norma 203B Chemistry
According to the Norma Reloading Handbook #1, Norma 203B has the following composition:
85% Nitrocellulose
7.5% Nitroglycerin
2.0% surface coating
4.6% Various chemicals
0.9% Water
3,957 J/g specific energy
890 g/l specific density
For comparison, the 7.5% NG component compares to 15% in Viht N500 series powders and 10% in Ramshot TAC / Big Game / Hunter.
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April 15th, 2019
The .260 Remington and the 6.5×55 Swedish (aka 6,5x55mm SE) are both very popular cartridges with hunters and target shooters. The 6.5×55 has a long military heritage and a great record as a hunting round. The .260 Rem, essentially a .308 Win necked down to .264 caliber, is a more recent cartridge, but it grows in popularity every year, being one of the top cartridges for tactical/practical competitions. It offers better ballistics and less recoil than the parent .308 Win cartridge. In our Shooter’s Forum, 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 6.5×55 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 (DBMs). If a bit more performance is needed, the .260 AI (photo right) can yield another 100-150 fps velocity, depending on bullet weight.
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July 9th, 2017
“The press is the heart of the handloading operation, also traditionally the most expensive single tool employed…” — Laurie Holland
British competitive shooter Laurie Holland has reviewed three popular, single-stage reloading presses for Target Shooter Magazine (targetshooter.co.uk). Laurie bolted up a Forster Co-Ax, RCBS Rock Chucker Supreme, and RCBS Summit to his reloading bench and put the three presses through their paces. These three machines are very different in design and operation. The venerable Rock Chucker is a classic heavy, cast-iron “O”- type press that offers lots of leverage for tough jobs. The smaller RCBS Summit press is an innovative “upside-down” design with a large center column and open front. It offers a small footprint and easy case access from the front. The Co-Ax is unique in many respects — dies slide in and out of the upper section which allows them to “float”. The cartridge case is held in the lower section by spring-loaded jaws rather than a conventional shell-holder.
If you are considering purchasing any one of these three presses, you should read Laurie’s article start to finish. He reviews the pros and cons of each press, after processing three different brands of brass on each machine. He discusses ergonomics, easy of use, press leverage, smoothness, priming function, and (most importantly), the ability to produce straight ammo with low run-out. The review includes interesting data on case-neck run-out (TIR) for RWS, Federal, and Norma 7x57mm brass.
Review Quick Highlights:
RCBS Rock Chucker Supreme
“My expectations of the antediluvian RCBS Rock Chucker Supreme’s performance weren’t over high to be honest as I mounted it in the place of the Summit. As soon as I sized the first of the stretched RWS cases though, I saw why this press has been such a long-running favorite. The workload was considerably reduced compared to the other two presses and doing 40-odd cases took no time at all with little sweat — it just eats hard-to-size brass.”
RCBS Summit Press
“Despite its massive build and long-stroke operating handle, [the Summit] took more sweat than I’d expected, even if it was somewhat less work than with the Co-Ax. Although the Summit is apparently massive, I noticed that the die platform would tilt fractionally under the heaviest strains[.] It is nevertheless a very pleasant press in use and bullet seating was a doddle — the few examples tried proving very concentric on checking them afterwards. The optional short handle would be valuable for this task.”
Forster Co-Ax
“[On the Co-Ax], the operating handle is above the machine, located centrally here [with] twin steel links at the top end of the press dropping down to the moving parts. The Co-Ax incorporates a number of novel features, principally its automatic and multi-case compatible shell-holder assembly with spring-loaded sliding jaws, very neat spent primer arrangements that allow hardly any gritty residues to escape and foul the moving parts and, the snap-in/out die fitment that allows rapid changes and also sees the die ‘float’ in relation to the case giving very concentric results. I own this press and it meets my handloading needs very well.”
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November 23rd, 2016
Here’s great news for mid-size cartridge fans, and especially PRS and tactical shooters. Lapua just announced it will produce 6.5 Creedmoor cartridge brass, which should be available in the first quarter of 2017. This premium-quality brass features a small primer, and 1.5mm flash hole (as found on Lapua’s 6mmBR, 6.5×47 Lapua, and 220 Russian brass). We expect Lapua’s 6.5 Creedmoor brass will set new standards for accuracy and case life for this popular mid-sized cartridge. Of course Lapua’s new 6.5 Creedmoor brass can also be necked down and loaded in 6mm Creedmoor configuration. With the small primer pocket and proven strength of Lapua brass, we think 6.5 Creedmoor shooters will see enhanced cartridge velocities with the ability to maintain tight primer pockets even with very stout loads. And we expect accuracy to be on a par with Lapua’s excellent 6.5×47 Lapua brass. Taken together, this is an exciting product release. Here is Lapua’s official announcement:
We are happy to announce the addition of the 6.5 Creedmoor case to the Lapua line! Despite a relatively short time on the marketplace, the 6.5 Creedmoor has made a tremendous splash in the field, rapidly becoming one of the most requested cases we hear about from shooters. Lapua’s 6.5 Creedmoor is designed to function in a short action, which is also a plus for hunters, vitally concerned with the rifle’s weight and compactness. In fact, many of the same features which make for a successful competition cartridge, translate nicely to the hunting fields as well.
For most species of mid-size game such as deer or boar, the Creedmoor will prove to be a deadly performer. And while the selection of high grade Match bullets in the 6.5 bore size is tremendous, there’s no shortage of exceptionally good hunting bullets either. The 6.5s as a group have always been known as excellent performers on game.
 Made with Lapua’s typical dedication to precision, our new 6.5 Creedmoor case has been refined just a bit, to make it an even better performer. We’ve opted for the small rifle primer, which normally produces an optimized ignition and better accuracy than large primers in mid-sized cartridges like the Creedmoor.
We’ve also incorporated our smaller-diameter flash hole (1.5mm, rather than the industry-standard 2.0mm), which has proven to provide enhanced accuracy, and is used in a number of our other accuracy-oriented cases. In this respect, the new 6.5 Creedmoor joins the ranks of our other dedicated accuracy cartridges such as the .220 Russian (6mm PPC), the 6mmBR Norma, the 6.5×47 Lapua, and the .308 Win Palma cases.
And naturally, the new 6.5 Creedmoor will be made with our well-known Passion for Precision. Strictest control over the metallurgy, the forming and drawing processes, precise annealing all performed under the watchful eyes of our production experts. For you, the handloader, that means the durability for which our cases are famous, combined with consistency and long life. Already proven in competition, we predict that the 6.5 Creedmoor will be a force to be reckoned with for many years to come.
Comment on Lapua’s new 6.5mm Creedmoor
Our British friend Laurie Holland was excited about the new 6.5 Creedmoor brass from Lapua: “With this and Peterson Cartridge on the bandwagon, plus another U.S. brass maker… the Creedmoor’s momentum is becoming impressive.” Laurie observes: “A small primer Lapua-cased 6.5mm Creedmoor is in effect a 6.5X47 Lapua ‘Improved’!” That’s a pretty interesting concept indeed. Which makes us wonder if the .260 Remington has finally been fully eclipsed. With Lapua 6.5 Creedmoor brass you can probably get very, very close to .260 Rem performance in a much more efficient case.
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March 30th, 2016
Are you a fan of 6.5mm rifle cartridges? Then you should visit TargetShooter Magazine and read Laurie Holland’s latest “magnum opus”. Laurie recounts the development of 6.5mm rifle cartridges and examines a host of “six-fives” including the well-known 6.5×55 Swede and more esoteric cartridges such as the 6.5×58 Vergueiro. Laurie looks at a variety of military 6.5mm cartridges, including Japan’s 6.5×50 Arisaka, as well as some big 6.5mm Magnums. This Editor shot a .260 Remington (essentially a necked down .308 Win) for quite a while. I was pleased to see that Laurie discusses the .260 Rem, along with its bigger brother, the 6.5-06.
Part One of a four-part series, this is a LONG article, which runs over 4000 words. There are more than a dozen photographs, showing both cartridge types and bullet types. In addition, cartridge specs are presented in two detailed tables. Here is a list of the notable 6.5mm cartridges Laurie references (and we may have missed a few):
6.5×47 Lapua
.260 Remington (6.5-08)
6.5×50 (Arisaka)
6.5×52 Carcano
6.5x53R Mannlicher
6.5×54 Mannlicher-Schoenauer
6.5×55 Swedish |
6.5×57 Mauser
6.5×58 Vergueiro
6.5×68 RWS
6.5-284 Norma
6.5-06 (6.5/.30-06)
6.5mm Remington Magnum
.264 Winchester Magnum |
In early 20th century the 6.5x54mm Mannlicher-Schoenauer was a highly-regarded hunting cartridge.
Here is a sample from Laurie’s 6.5mm Cartridge History:
The 6.5×55 Swedish Mauser and Other Early Designs
Thanks to the 6.5X55mm and its common name of ‘Swedish Mauser’ (it was a joint Swedish / Norwegian military development truth to tell), not forgetting first rate Lapua, Norma, and Sako ammunition and components, many associate the 6.5s with Scandinavian countries. However, the two Nordic nations weren’t alone in adopting 6.5mm designs during the back end of the 19th century, moreover Germany and Austria did as much to popularize the caliber. The Netherlands, Italy, Japan, Romania, Portugal and Greece took the small caliber military route too, although some later decided to convert at least partially to larger bores.
However, once armies started to adopt lighter, pointed bullets at improved velocities in the .30-class designs starting with the German 7.92mm 153gr bulleted S-Patrone of 1905 which produced the then astonishing MV of 2900 fps in the G98 rifle, the 6.5s lost out as contemporary propellants couldn’t handle smaller calibers as efficiently. It’s significant that while some early users moved to larger caliber service rifles, no country [other than Japan] has adopted 6.5mm in the last 110 years although there have been some unsuccessful initiatives recently.
Prior to WW2, there had only been a single American attempt to produce a 6.5, the brilliant cartridge designer and riflemaker Charles Newton with his eponymous 256 design of 1913 which used a shortened and necked-down 30-06 case. The Western Cartridge Company loaded ammunition for Newton, a 129gr expanding bullet at a claimed 2760 fps MV and obtained in a longer barrel than those fitted to production rifles.
RWS introduced the powerful 6.5X68mm in 1939 and it is still in use in Europe.
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September 13th, 2015
In response to our Bulletin story about the availability of Norma powders at Midsouth Shooters Supply, one of our Forum members asked: “I’m having trouble finding Reloder 15 for my 6.5×47 Lapua — should I consider running Norma 203B instead?” As we’ve explained before, these two powders, both made by Bofors in Europe, are very, very similar. Here are some hard numbers that should demonstrate how virtually identical these powders really are.
Target Shooter Magazine writer Laurie Holland compared Norma 203B and Reloder 15 using data from QuickLOAD. Laurie also checked load manuals to see how listed charge weights varied for the two propellants. Laurie concluded there was very little difference between Norma 203B and Reloder 15.
Norma 203B vs. Alliant Reloder 15
Commentary by Laurie Holland
Running [203B and RL15] through QuickLOAD doing a ‘charge table’ run for a 130gn Berger VLD at 2.700 COAL in 6.5X47 Lapua, gives very similar positions in the table [for both powders]. The charge required to achieve 62,000 psi estimated pressure varies by a mere 0.2 grains between the pair, Norma 203B being the heavier of the two. The estimated Muzzle Velocity (MV) also varies by a mere 2 fps, RL15 estimated to produce 2,946 fps MV compared to 2,944 fps for N203B at 62,000 psi (with the parameters I used).
If they aren’t the same thing, they’re so close as to make no difference and as Forum Boss points out, they’re made by the same people (Bofors) in the same plant.
[The Berger Reloading Manual includes data for both powders] for the .308 Winchester and heavier bullets (185 to 230 grains). Maximum charges and claimed MVs are not always identical, but are so close as to be marginally different production lots of the same thing, or maybe the result of minor testing variations.
.308 Win Max Charge Weights in Grains (RL15 / N203B) (Berger Manual)
MVs [for the four bullet types] are close but not identical, the largest difference being for the 210s which shows RL15 producing 2,428 fps MV v 2,383 for Norma 203B.
Norma 203B Chemistry
According to the Norma Reloading Handbook #1, Norma 203B has the following composition:
85% Nitrocellulose
7.5% Nitroglycerin
2.0% surface coating
4.6% Various chemicals
0.9% Water
3,957 J/g specific energy
890 g/l specific density
For comparison, the 7.5% NG component compares to 15% in Viht N500 series powders and 10% in Ramshot TAC / Big Game / Hunter.
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June 14th, 2015
The .260 Remington and the 6.5×55 Swedish (aka 6,5x55mm SE) are both very popular cartridges with hunters and target shooters. The 6.5×55 has a long military heritage and a great record as a hunting round. The .260 Rem, essentially a .308 Win necked down to .264 caliber, is a more recent cartridge, but it grows in popularity every year, being one of the top cartridges for tactical/practical competitions. It offers better ballistics and less recoil than the parent .308 Win cartridge. In our Shooter’s Forum, 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 6.5×55 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 (DBMs). If a bit more performance is needed, the .260 AI (photo right) can yield another 100-150 fps velocity, depending on bullet weight.
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June 3rd, 2015
Click Photo to read full test results in Target Shooter Magazine.
If you shoot a .308 Win, or any cartridge that uses a Large Rifle (LR) primer, you should read an important new article by Laurie Holland in Target Shooter Magazine. Holland, a talented shooter from the UK, tested no less than sixteen (16) different large primer types using a custom F-TR target rifle shot from the bench. Laurie loaded .308 Win ammo* with 16 LR primer varieties and then tested for average velocity, ES/SD, and group size. This may be the most comprehensive and thorough LR primer test ever done. Here are the primer types tested:
CBC Magtech 9½
CCI 200 LR
CCI BR2 Match
CCI 250 Magnum
Federal 210
Federal 210M Match
Federal 215M Magnum Match
Fiocchi Large Rifle |
Kynoch Large Rifle
Murom KVB-7 (PMC LR)
Norma Superflash LR
PMC LR Magnum
Remington 9½ LR
Remington 9½ M Magnum
Sellier & Bellot LR
Winchester WLR |
Test Rig: Osprey Rifles-built F-TR rifle with Savage PTA action, 32″ Bartlein 1:12″-twist ‘Heavy Palma’ barrel, and Dolphin Gun Company modular stock with an F-Open/Benchrest fore-end.
Some of Laurie’s results may surprise you. For example, would you guess that Sellier & Bellot primers had the lowest ES, by a significant margin? And get this, among ALL the primers tested, Rem 9½M Magnum primers produced the lowest velocity, while Rem 9½ LR (non-magnum) primers yielded the highest velocity. (The total velocity spread for all primers was 35 fps). That’s counter-intuitive and it’s odd that Rems were at opposite ends of the speed spectrum among ALL primers tested.
“The rationale for doing side-by-side tests is to see what effect primer choice has on ballistics, i.e. average velocities and MV consistency. There are a great many views on the subject, a few based on tests (including primer flame photography) but most apparently hearsay.” — Laurie Holland
Every serious hand-loader should definitely read the full test results to understand Laurie’s methodology and get all the details. This is an important test, with significant findings. But if you can’t spare the time right now, here are some highlights below:
Primer with Lowest Velocity: Remington 9½ M Magnum (2780 fps)
Primer with Highest Velocity: Remington 9½ LR (2815 fps)
Primer with Lowest ES/SD: Sellier & Bellot LR (12/3.1 fps)
Primer with Highest ES/SD: Remington 9½ M Magnum (47/14.0 fps)
Primer with Smallest Group Size: Remington 9½ LR (0.43″ average, three 5-shot groups)
Primer with Biggest Group Size: CBC Magtech 9½ (0.7″ average, three 5-shot groups)
Editor’s Comment: Laurie shot three, 5-shot groups at 100 yards with each primer type. The average group size for the top six primers varied by only 0.10″ (0.43″ to 0.53″), so one can’t conclude that one type is much better than another. Total group size variance (from best to worst) was 0.27″.
“The biggest surprise to me … came from an elderly (at least 10 years) lot of Czech Sellier & Bellot standard caps with an ES of 12 and SD of 3.1 fps, way below those of the nearest competitor. By contrast to the Fiocchis, they were an almost slack fit in the cases and this may have contributed to their consistent performance.” — Laurie Holland
NOTE: Values in chart are based on 15-Shot strings. The ES/SD numbers will therefore be higher than is typical with five-shot strings.
Testing 16 primer types was a huge task — we commend Laurie for his hard work and thoroughness. This extensive test is an important contribution to the “knowledge base” of precision shooting. Laurie’s findings will doubtless influence many hand-loaders who hope to produce more consistent ammunition, or achieve better accuracy. Credit should also be given to Target Shooter Magazine for publishing the results. Well done gentlemen…
*Reloading method for Test Ammo: “Test batches consisted of 16 or 17 rounds for each primer, charges thrown by an RCBS ChargeMaster and checked on lab-quality electronic scales, adjusted if necessary to within ± 0.04gn, so any charge weight variation would be under 0.1 grain which equates here to 5 fps.”
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September 22nd, 2014
One of our Forum Members has a .308 Win load that dips into the transonic speed range at 1000 yards. He is concerned that his bullets may lose accuracy as they slow to transonic speeds: “My target is at 1000 yards. How important to accuracy is it to keep the bullet supersonic (Mach 1.2) all the way to the target? How does slowing to transonic speeds in the last 100 yards or so affect accuracy?”
TargetShooter Magazine and AccurateShooter.com contributor Laurie Holland offers some practical answers to this important question, based on his his experience with .223 and .308-caliber bullets.
Thoughts on Accuracy and Transonic Bullet Speeds by Laurie Davidson.
There is no simple answer to the question “How do transonic speeds affect accuracy”. Some bullets manage OK, some not so well, some fail entirely, and I’ve never seen a guide as to which models do and which don’t. But we do have the ‘boat-tail angle rule’, anyway. Bryan Litz says the ideal boat-tail angle is 7-9°. Go much above 10° and it’s too steep for the air to follow the bullet sides around to the base. This seems to manifest itself as much increased drag and turbulence leading to instability in transonic flight.
It is this effect that has led to the common advice of “Don’t use 168gr 30-caliber bullets at 1000 yards”. That is misleading advice as it resulted from use of the 168gr Sierra ‘International’ (aka MatchKing) bullet with its 13-deg BT angle. (This was, originally, a specialized 300m design — there are various near copies on the market from Speer, Hornady and Nosler.) By contrast, Berger 168-grainers are designed as long-range bullets with 8.9, 8.5 and a really nice 7° angle on the BT, VLD and Hybrid respectively. Hornady A-Max 30-cal projectiles (other than the 208-grainer) fall into this enforced shorter-range bracket too thanks to their 12.6° (and greater) boat-tail angles. (155gr = 13.5°, 168gr = 12.87°, and 178gr = 12.6°.)
Even this boat-tail angle ‘rule’ doesn’t always seem to apply. Many older long-range Service Rifle shooters talk about good results at 1000 yards with some batches of 7.62mm match ammo in their 20″-barreled M14s using the 168gn SMK. I’ve successfully used Hornady and Sierra 168s at 1000 yards in 30-cal magnums which drive the bullets fast enough to keep out of trouble at this distance. This is still not recommended of course thanks to their low BCs compared to better long-range speciality bullets.
These four photos show the substantial changes in the shock ware and turbulence patterns for the same bullet at different velocities. The “M” stands for Mach and the numerical value represents the velocity of the bullet relative to the speed of sound at the time of the shot. Photos by Beat Kneubuehl.
Transonic Issues with .223 Rem in F-TR
I was much exercised by [concerns about transonic instability] in the early days of F-Class, when I was shooting a .223 Rem with 80-grainers at 2,800 fps MV or even a bit less. Even the optimistic G1 ballistic charts of the time said they’d be subsonic at 1000 yards. (Bryan Litz’s Point Mass Ballistic Solver 2.0’s program says 1,078 fps at 1000 yards at 2,800 fps MV in standard conditions for the SMK; below 1.2 MACH beyond a point somewhere around 780 yards.) In fact they shot fine in a large range of conditions apart from needing around 60% more windage allowance than 6.5mm projectiles [shot with a larger cartridge]. The biggest problem apart from my wind-reading skills was constantly getting out of the rhythm to call to have the target pulled as the pits crew didn’t hear the subsonic bullets and had trouble seeing their little holes.
In the early days of F-TR I used a 24″ barrel factory tactical rifle that was billed as F-TR ready — it wasn’t! The much touted 175gr Sierra MatchKing, as used in the US military M118LR sniper round, was allegedly good at 1000 yards at .308 velocities — but it wasn’t! It would group OK in [some calm] conditions, but any significant change would cause a much greater deflection on the target than the ballistic charts predicted, so transonic flight was obviously making it barely stable. I also suspect conditions on the day had a big effect as Litz’s program says [the 175gr SMK] is just subsonic at 2,650 fps MV at 1,000 in standard conditions. Throw in MV spread and there was a risk of some round remaining supersonic, while others went transonic. Plus warmer or colder air moving onto the range under some conditions might change things.
I used the combination on Scotland’s notorious Blair Atholl range at 1000 yards in one competition in a day of cold headwinds from the north and frequent rain squalls. The temperatures plummeted during the squalls (and the wind went mad too!) and what was an ‘interesting group pattern’ outside of squall conditions changed to seeing me do well to just stay on the target frame at all. On ranges other than Blair (which is electronic, so no pits crew), target markers reported they heard faint supersonic ‘crack’ and saw round holes on the paper, so the bullets appeared to remain stable and just supersonic in summer shooting conditions.
Transonic Problems with M118LR 7.62×51 Ammo
Confirmation of this transonic performance phenomenon has since come from USMC snipers who say the M118LR’s performance ‘falls off a cliff’ beyond 800m (875 yards), which is just what I found when shooting the bullet at slightly higher than M118LR muzzle velocities. A move to the 190gr SMK with Vihtavuori N550 keeping the MVs reasonable gave a vast improvement in 1000-yard performance.
Practical Advice — Use a Bullet That Stays Supersonic
The ‘easy’ / better answer to all this is to use a design such as the 30-caliber, 185gr Berger LRBT with a reputation for good long range performance and to load it to achieve or exceed 1,350 fps at 1000 yards. If I can get the combination I’m using to be predicted to hold 1,400 fps at this range in a G7-based program calculation, I’m happier still.
Incidentally, the old long-range, 30-cal Sierra bullets (the venerable 190gr, 200gr, and 220gr MatchKings), with their extra length boat-tail sections, have a superb reputation for stable transonic / subsonic flight. They were used by GB and British Commonwealth ‘Match Rifle’ shooters at 1000, 1100, and 1200 yards for many years before the current bunch of 210gr and up VLDs and Hybrids appeared.
 Transonic vs. Supersonic
The term “Transonic” refers to velocities in the range of Mach 0.8 to 1.0, i.e. 600–768 mph. It is formally defined as the range of speeds between the critical Mach number, when some parts of the airflow are supersonic, and a higher speed, typically near Mach 1.2, when the vast majority of the airflow is supersonic. Instability can occur at transonic speeds. Shock waves move through the air at the speed of sound. When an aircraft goes transonic and approaches the speed of sound, these shock waves build up in front of it to form a single, very large shock wave. This is dramatically illustrated in this Space Shuttle photo. |
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