AK Barrels - 4140 steel vs 4150 steel. This topic on barrels keeps coming back. As you may know, US military spec barrels in ARs are made from 4150, but somehow big barrels manufacturers, like Green Mountain Rifle Barrels, dont offer 4150 AK barrels. This is strange, because they do offer 4150 AR barrels, so they do have expertise and material to make these. Im not sure why they dont offer 4150, but I have tagged them in this post, so maybe they will stop by and say something. Now, why all of this matters? Here is one of the best quotes i have found on this subject: Unless you aim to hold the barrel at a temperature that exceeds the solution temperature for the alloy ie the quenching temperature for a significant period of time, the alloys 4140 and 4150 will behave in a near identical manner. It is virtually impossible to effect the grain structure of the steel at the temperatures found within even a heavily abused weapon. However the following are considerations in the selection of barrel steel The 4150 CMV alloy will allow more margin for error if an overload condition occurs equally they have a much greater resistance to cracking if a heated barrel is suddenly quenched by seawater, snow, etc. This said M2 barrels have been seen with cracks running the full length following one of the rifling grooves from waves hitting a hot gun At extreme cold levels the properties of 4150 CMV are desirable if the material is to exposed for significant time periods. It is this cold weather feature that is the primary driver in the material selection. The selection of essentially a specialized gun steel over a commercial AISI grade is always preferable for a safety critical part. Unless the barrel maker can undertake both chemical and microscopic examination of a rack grade steel it is possible that the barrel is manufactured from a coarse grained alloy. This will impact the toughness of the finished part. Now one has to ask, what are the chances that semi automatic AK will be exposed to such a drastic conditions? There is no way to simulate full auto fire on semi AK past 2nd magazine, because your trigger finger is going to be slowing down - i know, because i did this numerous times. So it is impossible to shoot close to full auto rate with semi auto AK for very long. Personally, Im not really worrying about not having 4150 barrel, but if someone would offer me one, i would probably pay little more for that piece of mind... As I said above, Green Mountain makes 4150 barrels for ARs...so it blows my mind why they dont offer 4150 for AKs...? I have no answer to this question. They already have material for it...so...why not to offer 4150 for slightly more? - Rob Ski
Posted on: Sat, 20 Dec 2014 14:46:15 +0000
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