K31 Swiss - Safety Issue

[uscra112]

Meandering about the Innertubes in the middle of the night, and came across this:

http://theswissriflesdotcommessageboard.yuku.com/topic/7021/K31-accidentSAFETY-CHECKS

The issue has to do with the lug on the operating rod which blocks the firing pin until the bolt is fully in battery.

I know I've been guilty of loading boolits so they have to be crowded home, which a turnbolt rifle does without hesitation, but the K31 does not. Dropping the striker when the bolt not 100% in battery would hammer this lug, and maybe cause it to break.

Very good pictures and commentary on the failure mode at the link.

Phil

[Czech_too]

Excellent write-up. I always 'try' to make sure that there is no gap between the receiver and bolt. My terminology may not be correct here. Regardless, now I'll have to take a look at the operating rod more often, or at least 'try' to remember to.

Brian

[Scharfschuetze]

That was a very well written article. I'll check those interrupter lugs from now on prior to shooting.

[Ray1946]

That's the only issue with the K31, the 1911's and the 1889's; they have virtually No camming power. In the K31 it could be a real issue as the interrupter lug has about 1/4 or 1/5 the mass of the same lug on the 1911 and the 1889. This simply means if you really get crazy and try to force the bolt shut on an improperly sized case of the bullet stick-out is too great, this little lug could break off and the rifle could be fired in an unlocked condition......BAD NEWS!
I am not trying to scare anybody; just be sure you size your case enough and seat your bullets deep enough so they chamber EASILY.................

[swheeler]

Thanks for posting

[MtGun44]

Look at the sn on the bolt. It will be straight up if fully locked.

Bill

[Hang Fire]

Read the article carefully, the problem arose from a change in the steel for operating rod/cam at the end of 1944. When the Swiss became aware of the failures, they retrofitted rifle’s operating rod/cam back to a better grade of steel. Not saying some could not have slipped through, but the chances of having a weak one is miniscule.

At the end of the war in 1944 the Swiss used a different steel for the operating rods and that was a reason for problems. The arsenals were ordered to replace these for better ones past the war and most got this modification but maybe this one slipped through.

[uscra112]

@ HangFire: Yeah, I caught that too, but regardless of the steel used, the design is intended for military ammo that fits fairly loosely in the chamber. Repeated pounding on the handle to seat overlong cartridges was probably not envisioned as normal use by the designers. And the consequences of a failure are dire enough that some attention to the detail seems warranted. I've looked at both of mine with a 32 power magnifier, I can assure you.