Updated: a day ago
6,5x55 6,5x51 6,5x49
(Swede Mauser) (.260 Rem) (6.5mm Creedmoor)
On the left is the 126 year old 6x5x55, still used every day all over the world - and together with the 128 year old 6,5x57 Mauser (not shown here) these two 6.5mm cartridges more than a century ago created the hunting standards still to be bettered in performance. They both stood the test of time and can only be equaled or "improved" on (lighter, therefore faster bullets - if that is seen as improvement) by cartridges employing markedly higher pressure.
Next to it is the American modern 6.5 mm based on the .308W case (51mm) and which should long ago have been the New World ballistic twin to the European 6,5 mms. Its slightly tapered case allows for its acceptable 60,000 psi Maximum Average Pressure and will always ensure easy extraction. Why Remington called it the Two-Sixty and not the 6.5mm-08 is unknown.
On the right is the 6.5 mm Creedmoor which, with its 62,000 psi is right on the heels of the old Europeans and the well thought out Remington regarding bullet velocity. In Africa where the application of these cartridges mainly is on plains game in the open, hot dry areas, the case with paralleled sides needed in order to achieve sufficient inside volume, combined with magnum pressure may cause difficult extraction if loaded too hot.
Question: Why is the Creedmoor's bullet seated out so far? To create a longer look for the short cartridge?
Here is a timeline of notable 6,5 mm offerings:
1889 - Italy: 6.5x52 Carcano: 140gr @ 2,600 ft/sec.
1892/3 - Germany: 6,5x57 140 gr @ 2,750+ ft/sec
1894 - Sweden: 6,5x55 140 gr @ 2,750+ ft/sec.
1897 - Japan: 6.5x50 Arisaka: 140 gr @ 2,550 ft/sec.
1904 - Portugal: 6,5x58 Verguiero: 155 gr @ 2,400 ft/sec.
1908 - Austria 6,5x54 Mannlicher Schönauer. 140 gr @ 2,550 ft/sec.
1927 - Germany: 6.5x64 Brenneke by H. Kepplinger: 140 gr @ 2,900 ft/sec.
1939 - Germany: 6.5x68 Schuler: 140 gr @ 3,100 ft/sec.
1959 - .264 Win Mag: 140 gr 3,000 ft/sec.
1997 - .260 Rem: 140 gr @ 2,740 ft/sec.
1997 - 6.5-06 A-Square: 140 gr @ 2,900 ft/sec.
2007 - 6.5mm Creedmoor: 140 gr @ 2,710 ft/sec.
As an outright statement regarding hunting, an honest review must immediately begin with: "Ignore the little differences in case geometry of the different cartridges (including the false dogma of 'shoulder angles'), and take the RIFLE with the nicest wood and neatest appearance and most reliable action; that one which draws your eyes immediately and speaks to you - particularly if it comes into your shoulder easily with the iron sights naturally lined up. No matter which 6.5mm cartridge it takes, it will be as good - in fact exactly the same - as any other one in the list".
Forget about the arguments that the 6.5x55 is better than both the 260 and Creedmoor - and the 6.5x57 is better than the Swede, and the 6.5x58 Portuguese is better than 6.5x57, and so on. Defining "better" by splitting hairs is an energy wasting infatuation with bickering - with paralyses by undending analyses as the only outcome.
In practice they are all the same. Once the bullet is flying (in fact even from one inch outside the case mouth where the maximum chamber pressure had been reached, the geometry of the combustion chamber (the case) that had spitted it out has nothing to do with its performance through the air or on the animal you are shooting at. At impact it is only him and his designed ability to withstand the heat release into the material he is made of during a sustained but exceedingly brief impulse on the low shoulder of the animal. That thermal heat released is by the kinetic energy it had carried and which must be translated into raw heat as the kineses comes to an end.
No matter the distance you shoot your mule deer at - the bullet from a 6.5mm Creedmoor impacts a deer the same as would a 6.5x57 Mauser had the deer been standing 12 yards further:
If the deer was another two yards closer a 6.5x55 bullet would impact like the 6.5x57 did that two yards further.
The 6.5x54 Mannlicher impacts the same as the Swede would have done five yards further.
The .260 Rem bullet impacts the same as the Swede have done three yards further.
The 6.5 Creedmoor bullet would strike as hard as the .260 Rem would do two yards closer .
The US gun media, when referring to the performance of the old European 6.5mm, 7mm and 8mm cartridges seems to have colluded to only list their original performance with the old, too fast propellants of 100 years earlier. Furthermore, the informal specifications adviser SAAMI downgraded each one of the European cartridges to such low pressure levels that they do not indicate even the old military performance, and certainly not their potential ability today.
One example is the 6.5x55 Swede.
In the real world of Europe and South Africa - where SAAMI advice on MAPs is not accepted - its case capacity allows it to outperform the .260 Rem by about 50 ft/sec with 140gr bullets and by 90 ft/sec with the long 156-160gr big game bullets. In the virtual world where any European action prior to the Mauser 1898 is deemed to be “weak” by SAAMI and gun "experts" on forums and YouTube, the superbly strong Karl Gustav 1894/1896 is limited to 51,000 psi while the .260 Rem and Creedmoor are rated for 61,000 psi.
In Europe and Africa the ability of the 6.5x55 and Karl Gustav action is well known and respected; that action is revered for what it is - one of the finest ever made with the strictest quality specifications, quality control processes and quality assurance testing. When the Swedes had the Carl Gustav rifle made under licence in Germany they insisted that only Swedish steel billets be used - not trusting the German quality control standards. Imagine saying that to German metallurgists...
CPI of Europe to this day demands that every single rifle (yes, every single one) with its cartridge has to be proof fired at 125% of the maximum pressure applied for.
Careful measurements are carried out to confirm all specifications with zero tolerance for any plastic deformation. To meet the same quality standard in the USA every single rifle chambered for the .270W plus 10 cartridges from each manufacturer would need to be be tested at 81,350 psi before being allowed to be sold. Of course this standard does not exist in the USA.
The 115 year old 6.5x55 '94 Carl Gustaf is factually ired at 71,000 psi, as an example. This means that European hand loaders consider 60,000-62,000 psi as a safe working pressure for these rifles and cartridges. Factory loads in Europe will be about 10,000 psi higher than US factory ammunition for the same cartridges.
My own introduction with the 6.5s was with a 6.5x58 Verqueiro (Portuguese Mauser) in the late 1970s. I was on a ranch against the Limpopo river bordering Botswana and the land owner asked me to find a good kudu bull as a taxidermist wanted RW horns.
I did not have my rifle so he gave me this old Mauser with open sights and two cartridges. I looked at those unusually long, thin, 160 gr round nose solid bullets and was convinced it would tumble the moment it impacted with the kudu's shoulder bones. Just before sunset I found a very nice bull. It jumped at the shot and fell down 20 yards on and died. The bullet had broken both shoulders, devastated the top chambers of the heart and was gone out the opposite side. I could not believe that penetration at the time. Now that I can calculate its relative pentration index I can assimilate the practical experiences hunters the world over have with the mathematics.
Look at this table of relative penetration impulse figures for the 6.5 bullets: