chrome moly vs. chrome lined


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ProCharger
January 21, 2004, 04:21 PM
What is the difference between the two? Advantages/disadvantages....

Brett

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AZ Jeff
January 21, 2004, 04:45 PM
All modern rifle barrels (except the stainless steel ones) are made from chrome molybdenum steels. This steel is chosen for it's toughness and machinability, plus it's ability to take various protective coatings (blueing, parkerizing, etc.)

Chrome lined barrels are just that: chrome molybdenum steel barrels that have been plated internally with an industrial chrome plating (NOT the bright stuff used on bathroom faucets and car bumpers.)

Chrome bores offer two characteristics that the military finds desireable:
1. easier to clean than plain steel barrels, as the chrome has less microfissures and pits for the fouling to accumulate in.
2. better resistance to bore erosion due to the hot propellant gases. This translates to longer barrel life, especially with automatic fire.

The DOWNSIDE to chrome bores is that they are NOT as uniform in internal dimensions as a plain chrome moly barrel. The plating of the chromium is not totally uniform in thickness, and thus, the internal dimensions of the barrel vary along the axis of the bore. For this reason, match rifles almost never have chrome plated bores.

To increase the durability of the barrel bore, and not sacrifice the consistency of the barrel machining dimensions, some match rifles are fitted with stainless steel barrels. The stainless steel is more resistant to bore erosion, but can be machined to have bore dimension consistency similar to that in chrome moly steels.

Gary G23
January 21, 2004, 05:01 PM
AZ Jeff is totally correct. I might add another advantage is that a chrome lined chamber can aid in reliability by making feeding and extraction smoother. Concerning accuracy I definitely would not choose a chrome lined barrel for CMP competition but there are plenty of chrome lined barrels that are accurate enough for IDPA or IPSC competition.

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