"The GP11 was never authorized for use in the Model 1889 rifle, and can only be used in adapted rifles, the Model 1896/11, although I've seen more than one recommendation that 1896/11s really aren't up to a steady diet of GP11 rounds. "
__________________
#6 is indeed an 1889. IF it was converted, it would have been to the common 30/30 conversion. easiest way to tell if you have no other........ try to chamber an inert round of 30/30.
The receiver of the 1889 is indeed strong, however........ the locking lugs on the bolt are at the rear, and the cartridge head is NOT supported enough by the bolt face to fire the more powerful GP11.
Mike, the 96/11 will, indeed, take a steady diet of 7.5x55 since the 96/11, the 1911. the k11, k31 and zfk55 were actually designed "around" the GP11 cartridge, making it the only military series of rifles to be designed around a cartridge instead of a cartridge being designed for a rifle.
I wrote this response maybe 25 or 30 years ago for a gent enquiring.
" Good day Erwin.
The k31 and it's mates, the 1911, k11 and the rare (in the US) zfk55 Swiss Sniper Rifle are a rarity in another category. A Military series of rifles designed around a specific cartridge for accuracy and performance.
The intent of this cartridge/rifle mating was to hit a human in the kill zone at range and they performed as intended. Not many production rifles are capable of doing that. The very great majority of these rifles perform
Are there rifles that outperform it? Of course there are, but none of them are a standard military issue firearm designed around a dedicated production cartridge for that rifle."
The most common of the conversions were of 96/11s and 1911s converted to .308 by Golden State Arms in the 70's. Those receivers are, indeed, more than strong enough for the 50,000+cpu of the .308.
Haemmerli manufactured the k31 in 7.5x55, .308, 30-06 (as a single shot) and 300 Winchester magnum. The steel in the receivers and barrels of those rifles is of a Rockwell hardness that it's an insane chore to drill. Far harder than any other military rifle manufactured. How do I know this? Because my company, for the past 17 years has manufactured after market accessories for Swiss Rifles. We're very involved in the metallurgy of these rifles.