Barrels: Chrome v. Chome-moly v. Nitride

the advantage of chrome lined barrels is that they drop the pressure which the ar-15 is very sensitive to. they also help with extraction of spent cases. the hard chrome lining helps barrels last longer. this is really helpful with some of the somewhat wear prone one in seven inch twist barrels.

lastly they clean up easy.

the disadvantage is they cost a bit more to make.

regular 4140 moly is just a regular barrel steel it will last a long long time with the most often used twist rate on one turn in 9 inches. it has an advantage is it is less difficult to cut the rifling in the 4140 than harder 4150 which makes for slightly better accuracy in theory. without the chrome they are finished a little more rough in the chamber. i have about as many ar-15 types with the 4140 without the chrome and they all function fine.

so the chrome is not a have to thing but it is nice to have IMHO.

stainless steel is also used for barrels. it is usually the most accurate though being a bit softer it wears a bit quicker. it should last plenty long on a sporting rifle.

the nitride is a type of finish --i figure the exterior finish is better--now about the bore i can't say as i haven't owned any nitride barrels. i would not rule it out as being a very good barrel though.

any of these should give years of accurate shots. the one that is best depends on what your use of the firearm is. tack-driver target shooting go with the stainless. survival-military get the chrome lined. all around use the moly or nitrite should do the job well.

Everything previously stated is correct. I will add the following:

Chrome-lined barrels are slightly less accurate due to the increased bore size that is required prior to the chrome-lining process. This also helps with the barrel's longevity. What the real difference is? No clue. Yes it makes a difference in accuracy beyond 200 meters. But not by much. Maybe an MOA. Maybe less. Chrome is more slick than steel, and copper, salts, and other fouling does not stick to it. Again, previous statements are all correct. This is one reason why the AK and SKS are both so reliable and idiot friendly.

Chrome-Moly is a reference to the alloy of the steel, again as previously stated. It's only real vulnerability is fouling. And some fouling is more corrosive than other fouling. Refer to barrel condition descriptions of "bright and shiney", "frosty", or "dark". These indicate various levels of corrosion damage. This type of barrel is usually the most accurate, all other factors remaining equal.

"Nitride" barrels are essentially the same as Chrome-Moly, but have undergone a plating process that creates a very tough surface strength. The obvious result is that is wears very well, and is purported to be very durable. The claim most often used is increased accuracy over a longer period of time. I tend to agree with this assessment since the "Nitride" process of surface hardening has been used in the performance automotive industry for better than 30 years for things like bearing surfaces, gears, and the like.

This is my opinion:

Chrome-Moly is the best all-around for sporting and general use. Think M-1 Garand or M-14, Mauser or Springfield 1903, SMLE or Mosin-Nagant. With "modern" non-corrosive primers, these barrels will last between 20,000 to 50,000 rounds with moderate loss of accuracy. The part of the barrel that wears out the fastest is at the throat, just beyond the chamber. With these "older" rifle designs, the barrel could be removed, and set-back a few thousands of an inch, and re-chambered during an arsenal re-build to restore accuracy. After WWII, this practice was essentially abandoned due to cost. A lot of the "Captured" Mausers from from the former Soviet Union were re-arsenaled in just this fashion, along with having markings obliterated, and being re-blued. The concept of counter-boring the muzzle has been well discussed on this forum, and will eliminate accuracy issues due to muzzle erosion or misuse of a cleaning rod. I have resuscitated a number of old Mosins, Enfields, and Mausers in this fashion, using a combination of these methods, returning factory or even better than factory accuracy to a 50+ year old dinosaur.

Chrome is Chrome. It is cool. It is tough. It is slick. It is somewhat more loose in terms of internal dimensions because it has to be bored and rifled a few thousandths larger than a standard barrel to compensate for the thickness of the chrome-plate. These barrels will take upwards of 40,000 rounds before losing significant accuracy. I have accurized many SKS rifles by simply setting the barrel back a few thousandths of an inch, and squaring the barrel shoulder and the receiver shoulder. In most cases, I do not have to adjust the chamber depth, in some cases, I have had to machine a new locking shoulder to adjust the head-space. I am sure that some of the "old-dogs" are spinning their heads around in a circle. Try it. I have yet to blow a case.

I have yet to actually shoot a known Nitride treated barrel. The possible exception would be late-model M-14 rifles that were selected for Counter Sniper rifles in the late 1970's and early 1980's, or purpose built early M-21 rifles. I have no certain knowledge of either from a design or armorers standpoint. Only as an end-user. If anyone knows for sure, I would like to know what you know. I could find no evidence of chrome-lining in these barrels.

That is my $ 0.02 with inflation.

Comments very welcome!!!

There are many names for nitride treatment (Glock=tennifer, melonite, hard blue, etc...). It is all pretty much the same result. The processes can differ from a hot bath to atmospheric heating in a chamber. This video is a decent example:
[video=youtube;yr8j8kZwXrc]http://www.youtube.com/watch?v=yr8j8kZwXrc]YouTube - Hard Blue Tough[/video]

Now guys, I am NOT a metallurgist or a chemical engineer, I just love to learn and research everything. Everything I've written here are the facts as I understand them. Basically they heat up the item in a high nitrogen-carbon rich environment. This allows a symmetrical case hardening of the material with the inner core metal at the same hardness levels. This allows a harder than chrome surface that is not brittle. This is not a new process, I believe there are some weapons from Switzerland or Sweden (always get them confused) that were nitride treated back around 1900's.

I personally believe that if done correctly, this is a superior product than chrome due to the fact that this cannot flake off, doesn't degrade accuracy, is harder (at minimum is as hard) as chrome, treats the entire structure (bore, port, outside, etc...), and can in theory make a less expensive barrel steel equal to any other in terms of function.