Some earlier Mk13's had their bolt faces opened up, others were already magnum bolt faces. It just depends on where the armorers at Crane sourced the guns, most were purchased through the military system, some were purchased out in town (if they really needed to get some rifles asap). It appears that the earliest guns didn't have the Sako extractor mod, but some later ones did. Mk13 build manuals from the mid 2000's call for the Sako style extractor, but it's hit or miss if a Mod 0 rifle at this time had this mod (not going to send a gun back to Crane just because it has a different extractor). Also, the manuals specifically mention the Tubb Speedlock Sako extractor, but the armorers at Crane used various brands over the years, whatever was available when they needed it. If you are building a Mod 0 clone, both types of extractors are correct, pick whichever you like best or match up to a earlier/later style built.
Here are 2 Mk13 Mod 0 marked bolts, which would mean that they came into the system later (because they didn't get a Mk13 Mod X designation until the mid 2000's)
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Here is a pic showing both of those marked bolts with the Sako style extractor
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This shows the later marked bolt above and earlier one without the modification below
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Closeup of the 2 bolts
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Here you can clearly see that the Sako extractor is located above the right lug as opposed to the regular Remington extractor which is located on the right lug. This has an effect on the direction the extracted brass will fly.
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