Silly question from a novice reloader. If the swede and CM shoot the same bullet. And the swede has the capacity for more powder.. is it not possible to get the same performance accuracy wise and realistically in the field / long range with the 6.5x55? Excluding the fact that the swede may be fractionally less efficient but don’t they basically come full circle to the same thing? Appreciate factory bought is a different game.
The larger the case and powder charge in relation to the bore size / area, the less efficient the cartridge (assuming same bullet, barrel length and maximum allowed pressure). The rule of thumb is that if you change case capacity by X% compared to another design in the same calibre, MV change = X divided by 4 %. So, to increase a hypothetical bullet's MV of 2,800 fps by 100 fps to 2,900 (a 3.57% increase) you need to increase the case size / charge weight by 3.57 X 4, or 14-15% give or take.
Of course, there are times when a larger case / charge are needed simply to increase MV / ME beyond a given point. So the 6.5X47 Lapua is more efficient than say the 6.5 PRC, but can't produce the same velocities
if they're needed.
'If they're needed' links into the action length marketing issue in the USA - to sell a long action sporting rifle in that market it has to accommodate a cartridge whose performance is such that it needs the greater length / capacity. As the 6.5X55 has no greater performance than the short-action orientated 260 or 6.5 Creedmoor models (less performance actually in its anemic US factory loadings) you simply can't sell long-action rifles chambered for it in the world's largest sporting rifle market.
The 6.5X55 is an anachronism (on paper at any rate) being as already pointed out in earlier posts an early 1890s design whose loadings / pressures were limited by action strengths and which needed a 55mm length case to accommodate the low-energy / bulky powders of that era. A similar example is the US 1906 30-06 Springfield with its 63mm case to give a 150gn bullet a mere 2,700 fps from a 24-inch barrel M1903 rifle, a velocity easily matched - and exceeded - by the much smaller 1950s design 7.62X51mm / 308 Win. As with many early military designs it'd be restricted to historic arms paper-punchers and a few deerstalking eccentrics if it weren't for regional historic reasons as traditionally 'hunters' adopted successful military designs. So Scandy sporting shooters kept the 6.5X55 alive, German (and some African) equivalents did the same for 8X57 and 7X57mm, Americans did for the 30-06 etc. (We're odd man out given the near complete loss of the 303 in stalking.)
In practical terms, as has been said again and again
(ad nauseum) 260 Rem, 6.5 Creedmoor, 6.5X47mm, 6.5X55m all do the same job on British deer and it comes down to whether you handload or buy your ammo, and if the latter then choice / availability / price. Creedmoor and 6.5X55 win out every time for the ammo buyer here; take you pick - for whatever reason - out of any of them if you handload. Match shooters have rather different criteria / requirements changing the process and results to some extent.
