Blow ups with S bore ammunition in J bore rifles are not a myth. The Germans themselves did several things on those rifles, and it depended on the State, as Germany was a Federation at the time. This information comes from
German Military Rifles Vol 2, Dieter Storz.
The expensive route was a new barrel and chamber. The barrel would be 0.323 and the chamber reamed for the 0.323 case neck and throat.
The midpriced option was a 318 barrel reamed out to 323 and rechambered.
The cheap skate method was to simply ream the chamber out to the larger cartridge, which must have included a larger case neck and throat. This was considered bad practice by some of the Federations and a discussion in the book, by the cheap skates doing this, was that their rechambered barrels did not blow up any more often than the reamed out barrel!s
At a Regional I got to talk to a guy who does investigations for firearms product liability lawsuits. The one that still upset him was the one dealing with a rare M1888 with the 0.318 barrel and 0.318 chamber. The rifle was sold by a distributor/importer as an 8mm Mauser, so the purchaser bought 8mm Mauser ammunition (0.323), and shot it. The bolt lugs sheared off, the bolt blew out, went completely through the shooter's jaw and shoulder! The teller of this tale shuddered when he recalled that there was still meat on the bolt when he investigated the wreck. The investigator had to look long and hard for an all original, unconverted M1888 as a standard, apparently they are very rare, the Germans must have been very diligent in converting all they could find.
Perhaps the reason you did not have a blow up is that your chambers were reamed out for the larger cartridge. Did you ever check to see if you have the original J bore chamber?
I would not recommend firing any of those
0.327 diameter "8mm" bullets in your M1888's, you might have an accident for real. I have a "8mm" Yugo M98 with a 0.327 barrel. The rifle is a German WW2 capture, rebuilt after the war with a new larger barrel. It did not shoot worth a flip with 0.323 and I finally figured out why when I drove a lead lap down the bore.
By the way, something I learned about from the investigator, is that all these lawsuits, the records are court sealed. You will never learn about them, and there is a good reason for this. Sellers of firearms don't want to encourage lawsuits by letting the public know how many people get hurt with their firearms. The product liability lawyers don't want to public to know, because they have their fishing lines in the stupid swamp, and don't want to scare the fish! Someone's injury is their gain!
