Modern Historical Intermediate Calibers 023: The 6.35/6.45x48mm Swiss GP80

Left to right: 7.65x38mm Swiss, 7.5x55 GP.11, 6.45x48mm GP.80, 5.56x45mm SS109

Left to right: 7.65x38mm Swiss, 7.5x55 GP.11, 6.45x48mm GP.80, 5.56x45mm SS109

Information on this round and the weapons designed to fire it is scarce, so the details in this article may be at times incorrect. Just letting you know. -NF

Before the SIG SG 550 was adopted by the Swiss Army as the Stgw. 90, there was another series of rifles, called the SG 540, which was developed by SIG as a new generation of infantry weapon. The 540 was produced in the 5.56x45mm caliber originally developed for the US AR-15 (not the later NATO-standard 62gr round), while the 542 variant was produced in 7.62 NATO caliber. The 541, in between the two, was produced in a unique experimental caliber, called at different times the 6.35 or 6.45x48mm GP80. This round is very similar in size and shape to 6.5mm rounds at various times proposed by different personalities as next-generation general purpose cartridges to replace both 5.56mm and 7.62mm, but the actual Swiss 6.35/6.45mm round was different than rounds like the 6.5 Grendel or .264 USA in that it used a light-for-caliber bullet fired at a high muzzle velocity. In fact, the Swiss 6.35/6.45 represents a sort of “big SCHV” paradigm that has not been seen elsewhere.

 

I have to admit, I don’t entirely know what the shape of the GP.80 projectile looks like (I own one of the rounds, but am not willing to pull the bullet!), and so the G7 BC I use here is really nothing more than an educated guess. Further, I am not sure exactly what barrel length the 2,950 ft/s muzzle velocity of the GP.80 cartridge was measured from. I have stated a 20.8″ barrel length here, since that is the barrel length of the 5.6mm Stgw. 90 that was eventually adopted.

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As you can see, performance in terms of velocity loss, drop, and drift are very similar to the 5.56mm caliber that was eventually adopted as the 5.6mm GP90 (functionally identical to 62gr 5.56×45 NATO). Energy is somewhat higher than that for 5.56mm, although the difference shrinks as range increases.

In terms of weight, the 6.35/6.45 Swiss is oddly heavy, at 19.4 grams. This is because of the large case (about the same size as today’s 6.5x47mm Lapua) relative to the round’s fairly modest performance. The reason for this is unknown, perhaps the Swiss intended to have a heavier alternate loading for long-range shooting.



Nathaniel F

Nathaniel is a history enthusiast and firearms hobbyist whose primary interest lies in military small arms technological developments beginning with the smokeless powder era. In addition to contributing to The Firearm Blog, he runs 196,800 Revolutions Per Minute, a blog devoted to modern small arms design and theory. He can be reached via email at nathaniel.f@staff.thefirearmblog.com.


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  • TechnoTriticale

    Picture caption missing or not visible for some reason, so can’t tell which is which.

    • I presume they are: 7.5x38mm GP47, 7.5x55mm GP11, 6.45x48mm GP80, and 5.56x45mm.

  • gunsandrockets

    Ballistics almost identical to .250 Savage. Case length is almost identical too.

    • FarmerB

      Well, I suppose the 5.6 version was close to the .22/250, which came from the 250 Savage so when they sized it up again….

  • Tony Williams

    At the ECRA International meeting last week I picked up a booklet on the programme (and especially the ammo) by a Swiss ammo collector. What follows comes from this.

    The Swiss assault rifle project was rather complicated. The first effort was in the 1970s and involved the 5.6mm Eiger cartridge, a powerful 5.6×48 with the same body diameter as the 7.62×51.

    This failed and was replaced by the 6.45×48, actually of 6.35mm (.250) bore, which used a necked-up version of the Eiger case. Many different bullet types were tested, but they were all relatively light (75 to 95 grains). Propellant loads were in the 41 to 42.4 grains range.

    The round, and the SG E22 gun to fire it, was developed by Waffen Fabrik Bern (W + F Bern). This rifle was delivered for troop trials in 1982, along with SIG 541 and the W + F SG 42, both in 5.56×45.

    The SG E22 was designated by the army the Stgw 80, and the 6.45mm cartridge the GP 80. Both were dropped early in the trials, due to the weight of the round and the benefits of standardisation with NATO.

    In 1983 the Swiss selected the SG SIG 541 in 5.56mm and designated it the Stgw90, with the ammo (which has a 69 grain bullet) designated the GP 90.

    The 6.45mm ammo and guns are still around. A few years ago the ECRA International was held in Switzerland (an event I unfortunately missed) and the visitors were given Stgw 90 to shoot….. presumably, they wanted to use up the ammo!

  • Quest

    I think a recoil chart in those articles also would be good.