8×68mm S: Difference between revisions

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The 8 x 68 S rifle cartridge (the S stands for Spitz and also means it is intended for 8.2 mm (.323 in) groove diameter bullets) and its necked down sister cartridge the 6.5 x 68 (no S or anything else required) were developed in the 1930-ties by Mr. Schüler from the August Schüler Waffenfabrik, Suhl, Germany as magnum hunting cartridges that would just fit and function in standard sized Mauser 98 bolt action rifles. This is one of the early examples where a de novo rifle cartridge (the 8 x 68 S and 6.5 x 68 have no other cartridge as parent case) was developed by a gunsmith to fit a specific popular and widespread type of rifle.

History

The German ammunition manufacturer RWS (Rheinisch-Westfälischen Sprengstoff factories) introduced both cartridges commercially in the spring of 1939. With the official certification of the .375 Hölderlin this German 68 mm "family" of magnum rifle cartridges that all share the same basic cartridge case got expanded 68 years later.

The cartridges in this German 68 mm cartridge "family" are, in the order of development:

8 x 68 S (1939)
6.5 x 68 (1939)
.375 Hölderlin (2007)

Standard military 7.92x57 mm Mauser 98(k) rifles have to be adapted by a competent gunsmith to function properly with these magnum cartridges since they are longer and the cases have a larger diameter then 7.92x57 mm Mauser cartridges. The 7.92x57 mm Mauser cartridge is also known as the 8 mm Mauser or in Germany as the 8x57 IS (IS stands for Infantrie Spitz). In adapted standard military Mauser 98k rifles the large 8 x 68 S cartridges are however praised for very smooth and reliable feeding.

The widespread availability of standard size Mauser 98 rifles and the fact that the .375 H&H Magnum cartridge and its necked down version the .300 H&H Magnum with approximately 72.4 mm case length were to long to fit in standard sized Mauser 98 bolt action rifles makes the shorter 8 x 68 S, 6.5 x 68 and .375 Hölderlin interesting chambering options.

World War 2 spoiled the commercial introduction and spread of the 8 x 68 S amongst German hunters. The cartridge became due to its high performance and flat trajectory popular after Word War 2 when German hunters were allowed again the own and hunt with full bore rifles. The 8 x 68 S performance also made that hunters who had problems with handling magnum cartridge recoil stepped down to less powerful but for German conditions adequate medium cartridges like the 7.92x57 mm Mauser, 7 x 64 (Brenneke) or .30-06 Springfield (also know as the 7.62 x 63 in metric countries). Recoil sensitive shooters can fit an efficient muzzle brake to significantly reduce the amount of recoil. With the help of a muzzle brake the 8 x 68 S recoil is reduced to tolerable levels.

Cartridge Drawing and Dimensions

Extremely thick brass results in 'only' 5.584 ml (86.0 grains) H2O cartridge case capacity for the 8 x 68 S. A rare feature of this German rimless bottlenecked centerfire cartridge design is that it has a slightly rebated rim (P1-R1 = 0.3 mm). A sign of the era in which the 8 x 68 S was developed are the gently sloped shoulders. The exterior shape of the case was designed to promote reliable case feeding and extraction in bolt action rifles, under extreme conditions.

8 x 68 S maximum cartridge dimensions. All sizes in millimeters (mm). Americans would define the shoulder angle at alpha/2 ≈ 14.53 degrees.

According to the official with CIP (Commission Internationale Permanente Pour L'Epreuve Des Armes A Feu Portative) guidelines the 8 x 68 S case can handle up to 440 MPa (63817 psi) piezo pressure. In CIP regulated countries every rifle cartridge combo has to be proofed at 125% of this maximum CIP pressure to certify for sale to consumers.

The American .325 WSM cartridge introduced in 2005 is probably the closest ballistic twin of the 8 x 68 S. The .325 WSM is considerably shorter and fatter and has a more radical rebated rim (P1-R1 = 0.51 mm), much steeper shoulder angle (70 degrees / 35 degrees for Americans) and a shorter neck (7.82 mm). This makes the 8 x 68 S case with its 9.11 mm long neck better suited for loading long heavier bullets and due to its sleeker exterior shape bound to cycle more reliable in bolt action rifles in extreme situations.

The 8 x 68 S in Field Use

German big game hunters often use 8 x 68 S rifles in Africa for hunting plains game, where American hunters would choose one of the .30 or .338 magnum cartridges. The 8 x 68 S as a pure civil cartridge can be used in countries which ban civil use of former or current military ammunition.

Since there are not much factory loads available (RWS offers 2 factory loads) and due to its good field reputation and efficiency, the 8 x 68 S is often used by reloaders. They have used this cartridge extensively to create powerful loads by handloading. Whilst staying within the 440 MPa CIP limit a 8 x 68 S rifle with a 650 mm (25.59 in) long barrel and appropriate modern gunpowder (Vihtavuori N560) can be handloaded to propel a 12.96 gram (200 gr) 8 mm bullet like the Sierra MatchKing to a muzzle velocity of 927 m/s (3042 ft/s).

Maximum muzzle velocity comparison in % of the probably most proliferated European and American 8 mm rifle cartridges out of 650 mm (25.59 in) long barrels loaded with relatively light to heavy 8 mm bullets to their CIP or SAAMI (Sporting Arms and Ammunition Manufacturers’ Institute) sanctioned maximum pressures.

Bullet weight gram (grain)	8.23 gram (127 gr)	9.72 gram (150 gr)	11.34 gram (175 gr)	12.96 gram (200 gr)	14.26 gram (220 gr)	Case capacity (%)
7.92x57 mm Mauser (8 x 57 IS)	100.00	100.00	100.00	100.00	100.00	100.00
.325 WSM	108.67	109.12	109.01	109.30	111.14	131.73
8 x 68 S	108.38	108.50	108.68	110.49	112.27	136.49
8 mm Rem. Mag.	111.89	112.33	114.46	115.26	116.02	157.13

This comparison is not totally objective since the 8 mm Remington Magnum and .325 WSM operate at 448.16 MPa (65000 psi), the 8 x 68 S at 440 MPa (58740 psi) and the 7.92x57 mm Mauser at 390 MPa (56564 psi). Higher pressure results in higher muzzle velocities.

The 8 x 68 S has a good long range accuracy reputation i.e. it is not hard to develop or find loads that will shoot 1 MoA or better out of decent standard mass produced rifles. Factory 8 x 68 S rifles often have a 650 mm or 26 in barrel with a 280 mm (1 in 11 in) twist rate, which works well in daily life. This twist rate was chosen since the bullet jackets used in the 1930-ties were not strong enough to cope with the forces generated by the magnum muzzle velocities of the 8 x 68 S. The 240 mm (1 in 9.45 in) twist rate normally fond in the 7.92x57 mm Mauser makes the 8 x 68 S combined with modern bullets with jackets designed for magnum cartridges an awesome long range cartridge.

Reloaders use the 8 x 68 S as a Jack of all trades cartridge on all European game from fox, roe deer and chamois upwards to the big European game like red deer, moose and brown bear. These people realized that bullets with different characteristics can be utilized to produce varying effects on game. They also realized that from 8 mm caliber upwards the rise of sectional density and penetrating capability of practical spin stabilized rifle bullets (bullets up to 5 to 5.5 calibers in length) tends to flatten out.

This means that loaded with light, short and soft nosed 8 mm bullets the 8 x 68 S can be used on remarkable small game. Loaded with heavy, long and hard (solid copper) bullets the 8 x 68 S offers enough speed derived power to penetrate heavy and dangerous game. The 8 x 68 S is suitable for hunting almost any game animal on the planet, though certain sub-saharan Africa countries have a 9.53 mm (.375 in) minimum caliber rule for hunting Big Five game - i.e. leopard, lion, cape buffalo, rhino and elephant. In the Central African Republic, where there are no ammunition limits for hunting Big Five game, the 8 x 68 S is used successfully for hunting elephant.

The 8 x 68 S as Parent Case

The .375 Hölderlin

The 8 x 68 S case has functioned as the parent case for the .375 Hölderlin (9.5 x 68), which is essentially a 9.525 mm (.375 caliber) necked-up version of the 8 x 68 S. The wildcat status of the .375 Hölderlin ended in 2007 when it got CIP certified and became an officially officially registered and sanctioned member of the German 68 mm "family" of magnum rifle cartridges. If the .375 Hölderlin will become available as factory ammunition, like the older cartridge "family" members (8 x 68 S and 6.5 x 68), is still unknown.

.375 Hölderlin maximum cartridge dimensions. All sizes in millimeters (mm). Americans would define the shoulder angle at alpha/2 ≈ 14.53 degrees.

The .375 Hölderlin has 5.65 ml (87.02 grains) water cartridge case capacity. According to the official CIP guidelines the .375 Hölderlin case can handle up to 440 MPa (63,816 psi) piezo pressure.

According to the creator of the .375 Hölderlin, Mr. C. Otterbein, the idea behind the .375 Hölderlin was to develop a big game cartridge based on a German cartridge case for standard sized Mauser 98 bolt action rifles. The ballistic performance had to be close to or equal the performance of the .375 H&H Magnum. The 8 x 68 S was chosen as parent case, since it offers enough case capacity and a competent gunsmith can relatively easy rechamber a standard Mauser 98 rifle to accept 8 x 68 S based cartridges. To keep costs down and promote an acceptable recoil level blowing out the parent case was renounced.

Wildcats

Cartridges that are not officially registered with nor sanctioned by CIP (Commission Internationale Permanente Pour L'Epreuve Des Armes A Feu Portative) or its American equivalent, SAAMI (Sporting Arms and Ammunition Manufacturers’ Institute) are generally known as wildcats. By blowing out standard factory cases the wildcatter generally hopes to gain extra muzzle velocity by increasing the case capacity of the factory parent cartridge case by a few percent. Practically there can be some muzzle velocity gained by this method, but the measured results between parent cartridges and their 'improved' wildcat offspring is often marginal. Besides changing the shape and internal volume of the parent cartridge case, wildcatters also can change the original caliber. A reason to change the original caliber can be to comply with a minimal permitted caliber or bullet weight for the legal hunting of certain species of game.

Wildcats are not governed by CIP or SAAMI rules so wildcatters can capitalize the achievable high operating pressures. It is often reported that modern 68 mm RWS brass can tolerate up to 500 MPa (72519 psi) piezo pressure. Because the 8 x 68 S offers an exceptional sturdy, pressure resistant cartridge case that can relatively easily be reloaded with primers, powder and bullets and hence be reused several times it has become quite popular amongst wildcatters. With the 8 x 68 S as the parent case wildcatters have created .25 x 68, .270 x 68, 7 x 68, .30 x 68, .338 x 68, .375 x 68 or .416 x 68 variants. Improved or blown out 68 mm cartridge designs are reported to come performance wise close to the 8 mm Remington Magnum which has about 14% more case capacity then the standard 8 x 68 S.

Examples of 8 x 68 S based wildcats are the relatively well know American 7 mm and .30 caliber Boo Boo and 7 mm and .30 HV wildcats. The Boo Boo wildcats were developed for long range target shooting were participants usually handload their ammunition. Several 1,000 yard shooting competitions have been won with Boo Boo wildcats. A wildcat from Europe that uses the 8 x 68 S as its parent case is the .30 Kovacs. It was designed in 1996 by Stefan Kovács, Austria-7041 Wulkaprodersdorf. The .30 Kovacs has much more powder-room (longer L2, wider P2, 40 degree Ackley-shoulder) then its parental case. It falls powder-room-wise between the .300 Winchester Magnum and .300 Wby. Mag. but has energy and velocity falling between .300 Weatherby Magnum and the .300 Remington Ultra Magnum. This wildcat cartridge will be fitted only by Büchsenmachermeister Egon Kriebernegg, AUSTRIA, 7000 Eisenstadt (see web-site) contact: skbullets@hotmail.com or look at www.kriebernegg.com.

External Links and Sources

@@ Line 29: / Line 29: @@
 German [[big game]] hunters often use 8 x 68 S rifles in Africa for hunting [[plains game]], where American hunters would choose one of the .30 or .338 magnum cartridges. The 8 x 68 S as a pure civil cartridge can be used in countries which ban civil use of former or current military ammunition.
-Since there are not much factory loads available ([http://www.rws-munition.de/en/rws_ruag/rws_ruag.htm RWS] offers 2 factory loads) and due to its good field reputation and efficiency, the 8 x 68 S is often used by [[reload]]ers. They have used this cartridge extensively to create powerful loads by [[handloading]]. Whilst staying within the 440 MPa CIP limit a 8 x 68 S rifle with a 650 mm (25.59 in) long barrel and appropriate modern [[gunpowder]] (Vihtavuori N560) can be handloaded to propel a 12.96 gram (200 gr) 8 mm bullet like the Sierra MatchKing to a muzzle velocity of 927 m/s (3042 fps).
+Since there are not much factory loads available ([http://www.rws-munition.de/en/rws_ruag/rws_ruag.htm RWS] offers 2 factory loads) and due to its good field reputation and efficiency, the 8 x 68 S is often used by [[reload]]ers. They have used this cartridge extensively to create powerful loads by [[handloading]]. Whilst staying within the 440 MPa CIP limit a 8 x 68 S rifle with a 650 mm (25.59 in) long barrel and appropriate modern [[gunpowder]] (Vihtavuori N560) can be handloaded to propel a 12.96 gram (200 gr) 8 mm bullet like the Sierra MatchKing to a muzzle velocity of 927 m/s (3042 ft/s).
 Maximum muzzle velocity comparison in % of the probably most proliferated European and American 8 mm rifle cartridges out of 650 mm (25.59 in) long barrels loaded with relatively light to heavy 8 mm bullets to their [[CIP]] or [[SAAMI]] (Sporting Arms and Ammunition Manufacturers’ Institute) sanctioned maximum pressures.