The only benefit to plated bolts is that they clean easier.
The major drawback to plated bolts is that they are now harder than the barrel extension, which means your barrel's headspace wears out quicker. In a normal barrel/bolt setup the bolt has a slightly lower rockwell hardness than the barrel extension to prevent this from happeneing.
Now, would you rather replace a fourty dollar bolt or a three hundred dollar barrel? Ease of cleaning is hardly worth the extra cost.
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The M-16 is a damn fine weapon, but your best, your most lethal and effective weapon is between your ears. Ssgt Brown, Parris Island, 3rd Bn, H co. 1984.