7.5 Swiss
Anybody know what a 7.5 Swiss equates to in inches?? I guess I could get out my calculator and figure it out, but I don't really know how many millimeters 7.5 Swiss really is (that and I'm being lazy). My guess is it's not exactly 7.5.
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gunluv280,
It is supposedly the land to land measurement of a .30 cal. If you reload for the 7.5 Swiss, and I do, you will note they use standard .308 dia. bullets.
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You gessed right. Bore diameter of the 7.5 Swis is .308. 0 -
gunluv280,
I'm on the run again this morning but I thought that I would add a bit from my notes.
The History The 7.5 Swiss Cartridge
In the early 1880s, Eduard Rubin designed the first successful small-caliber copper-jacketed bullets. These were capable of withstanding velocities that well exceed those of the rounds that were in use at the time. In 1882, Rubin's cartridges competed with Hebler pattern cartridges whose core was composed of paper-mache. While the Hebler rounds were faster, the Rubin rounds proved to be more accurate.
In 1884, 130 Vetterli rifles were converted to fire 7.5mm and 8mm rounds. And in 1885, the first pairing of a Rubin cartridge and Schmidt straight-pull action occurred. Over the next four years over a hundred rifles and at least 6 different rounds were tested. Finally, in 1889 a rifle and cartridge were decided upon.
The 7.5x53.5, .304 inch diameter, GP1890 was adopted along with the Schmidt-Rubin Model 1889 Rifle. The GP1890 used approximately 29 grains of a semi-smokeless powder and fired a paper patched 211gr round-nosed Steel-capped Lead bullet at approximately 1970fps.
Several years later the cartridge was upgraded. It was discovered that the original primer in the GP1890 was too corrosive. Consequently, the round was redesigned with a newer, less corrosive primer. The new round was designated the GP1890/03.
Later, in 1923, the GP1890/03 round was again modified. The new round, designated the GP1890/23 fired a 190gr CuproNickel Jacketed Lead round nose bullet and used smokeless powder. In addition, the round was lengthened to 54.5mm. The GP1890/23 generated around 37,000 psi. The GP90/23 round was available into the 1950s, and is the cartridge of choice for pre-1911 modified Schmidt-Rubins.
The biggest failing of the Schmidt-Rubin designed proved not to be the cartridge, but the action of the rifle. The inherent weakness of the design became apparent as the Swiss began experimenting with higher velocity rounds. However, by 1913 the action of the Schmidt-Rubin had been sufficiently strengthened to allow the next step in the development of the 7.5 Swiss round.
The GP11 was load with a 174 grain spitzer bullet. The round could travel at 2640 fps. The diameter of the bullet was increase, and the length of the case was increased to 55m. The GP11 generates around 45,500 psi of pressure. Most older Schmidt-Rubins were converted to fire the GP11, and the round saw service with the 1911 series, the K31 series, and the Stgw 57 series, remaining in service until the mid-1980s. Due to the greater pressures produced by the GP11 round, it is not safe to fire GP11 rounds in Model 1889 Schmidt-Rubins!!!
In addition to the standard FMJ GP11 rounds, specialty rounds were produced as well. Armor-piercing Steel-cored rounds can be identified by their violet bases. These rounds can easily pierce .2" of steel plate at 550 yards. Tracer rounds burn out to 880 yards, and can be identified by their red bases. However, most Swiss match shooters use standard GP11 ammunition, a testament to the accuracy of the GP11 round.
The headstamps on GP11 rounds can be read as thus; The numbers at the top and bottom of the case represents the month and year of manufacture, respectively. The letter to the left of the headstamp represents where the case was manufactured, while the letter to the right represent the finally assembly point of the cartridge. Letters used include D=Dornach, A=Altdorf, and T=Thun.
As a curious side note: according to an article on Cruffler.com. The Swiss GP11 bullet strongly influenced the design of the M1 .30-06 round.
Norma is the second company to produce loads the for the 7.5 Swiss round. They have a 190 gr. hollowpoint round with a velocity of 2592 fps. A 200 gr hollowpoint round with a velocity of 2493 fps. And a 180 gr soft-point round with a velocity of 2651 fps. Norma tends to be much more expensive, currently street prices range from $27 to $35, but it is also more accurate.
The Norma loads offer performance similar to the 7.62 NATO round, and at least one source reports the hollowpoint round performs well as a hunting round.
Finally, Ruag, the manufacturer of Swiss ammunition, also produces a line of Match grade ammunition. It is believed a lot SM Match Grade is about to be imported into the US.
Today, 7.5 ammo is finally becoming fairly easy to find. Several companies, are now importing GP11 ammunition. GP11 ammuntion is Berdan primed, and not easily reloadable. In addition, there are other alternatives. The first, was from INDEP of Portugal. The INDEP round is a 180gr round, traveling at around 1950fps. INEP ammuntion is no longer available, but Prvi Partisan is similar, and available from various sources.
Bullet Diameter
.3208" (w/ paper patch) GP90
.3208" (w/ paper patch) GP90/03
.3075" GP90/23
.3086" GP11
A little bit of background never hurt anything...
Best.
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nononsense, thanks for the great info. I enjoy having background info on older guns in my collection and this helps me understand my K31 better. Have a great day.
[8D][8D][8D]
A BAD DAY OF HUNTING IS BETTER THAN A GOOD DAY AT WORK!
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Ref: 7.5 Swiss- this has one of the BEST ballistic coefficents on any round loaded. In my wallet is a clipped out section of 100 meter target, with 4 ea 7.5 mm holes in a bit less than an inch. With surplus ammo and a surplus rifle, that ain't bad!
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You should try www.swissrifles.com
they can answer any and all questions that refer to any rifle that was ever used in the swiss service and the ammunition as well.
Veritas vincit "Truth conquers"0
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