Just a few caveats.
While it's safe to fire the shorter shell in the longer chamber, continued use will eventually result in chamber wall corrosion from the hot powder gasses, just ahead of the short shell's opened case mouth that will cause no end of extraction difficulties if/when someone ever want to use the longer ammo again.
I don't mean the fouling that normal cleaning will remove, I mean multiple, repeated, microscopic metal displacements.
And, the shorter shells may/may not, feed properly through, from the magazine.
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