6.5x55mm Swedish

Sweden and Norway were separate armies under one crown in 1891, and they set out to choose separate rifles firing one cartridge. The joint commission that resulted spent two years arguing calibre and case, and settled on a shallow-shouldered rimless 6.5 mm round that was standardised in 1893 and issued from 1894 — the Norwegians in a Krag–Jørgensen, the Swedes in a Mauser. It outlived the union by ninety years and is still loaded commercially.

The design decision that matters is the case, not the bullet. At 55 mm it is short for a full-power military round of its generation, but it is nearly parallel-sided with only a slight shoulder and a long neck, so a very long bullet can be seated deep in the neck without stealing powder space. That is what made the 10.1-gram round-nose service ball possible: an unusually heavy projectile for a 6.71 mm bore, which gives the round a high sectional density and a flat enough retained-velocity curve that Scandinavian target shooters kept using it long after the army had moved on. The 12.2 mm base is also generous for the calibre, which is why a bolt face cut for it accepts the .30-06 family of case heads and why the chambering appears in so many post-war commercial actions.

The service load changed once. The 1894 round-nose projectile was replaced from 1941 by a 9.1-gram boat-tail spitzer, developed for the m/41 sniper rifle and immediately adopted as the general service ball; the two are recorded here as separate loads because they are separate projectiles in the same case, fired from the same 739 mm barrel to different velocities.

Gaps on this page: the two service-ball figures come from the encyclopedia’s account rather than from a Swedish ordnance manual, which is not online in a form that can be linked. The article also reports a 1960 Swedish service pressure of 3300 bar without saying how it was measured, so that figure is not recorded — the pressure here is the C.I.P. commercial maximum, and SAAMI’s figure for the same chambering is lower, which is noted with it rather than stored as a second value. The rifling twist rate Swedish barrels were cut to is a property of the rifle rather than the cartridge and is not a field here.