Unexpected find, Argentine M91 DWM in 5.56mm NATO caliber

A friend got this Mauser at auction for a low price because it was mismatched and had scope mount holes. Examination at home showed the blocked magazine and eventually we figured out that it had been sleeved to 5.56 NATO/.223 Remington. It is unmarked, we don't know who did it. Ball ammo feeds okay but dimpled dummy .223 erratically feed. I like odd ball stuff. There are no markings as to who might have done this conversion.

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Very interesting, how was the bolt face altered and extractor/ejector. Sort of like the Lee Enfield No 4 conversions to 223 Rem a few years ago