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Old February 11, 2013, 03:29 PM   #3
blfuller
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Join Date: January 8, 2013
Location: Washington State
Posts: 192
It all depends on the grit used when the abrasive blasted the parts. The Colt are all hard anodized as well. The interior of the Colt upper had a dry lube applied to the inner diameter which is why it is slick. Since the Colt is made from a forging and the SI was machined from bar stock the SI will probably be rougher. The forgings are pretty smooth and to remove any machine marks they probably had to use abrasive blasting on the SI receivers.

The thickness of the hard anodizing also will determine how smooth it is. Hard anodizing builds up on the surface and also penetrates into the base metal. Another factor is the alloy used. Colt Mil spec typically used 7075 T6 forgings.

As far as it mattering, probably doesn't as long as they did per the specification. The thicker hard coat will probably wear better. Some are dyed black after anodizing and some are have a painted on finish. The early Colts are grayish which may be the natural hard coat. Age may have a factor as well depending how many times it has been cleaned, etc.
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