Stainless vs Chromoly
I figure this has been discussed before but, is there a significant difference between (416) stainless and chromoly barrels. I'm looking at getting a 16inch M-4 style barrel and wasn't for sure. The one I'm looking at is nitride treated for what it's worth. It won't have tens of thousands of rounds thru it and it wouldn't be for competitive shooting, but I would like it to be accurate and last a while. Thanks dannym
Happy with our Kreiger stainless 1"-7" on our WhiteOakPrec service rifle that John built for the youngest kid. You might ask Maury over on the Firing Line board or on the 1903 board on this.
There are so very many good barrel makers out there, that if any of em made that barrel, it should give you years of good service no matter what steel was used.
Had a retired US Army armorer build us a match M1A, and Jerry insisted on using a blued
Shilen barrel on it, and my brother in law shoots sub minute groups with it @ 600 yds.
on the application you intend the barrel for. For a true match barrel, the stainless steels commonly used offer the advantage of better average bore finish, which is why most serious match shooters use SS barrels. Either material can be used to produce an excellent barrel, if the manufacturer takes the trouble to make it so.
Chrome-moly is an excellent steel for rifle barrels in general, but I wouldn't pay a cent extra for nitriding or any other special bore treatment (except hard chrome, and then only for military application). The advantage claimed for nitriding or any other process which hardens the surface of the bore (longer barrel life) is based on a false premise: that the reason barrels wear out is due to mechanical wear or erosion of softer materials due to high temperatures and high pressures, whereas the actual failure mode is due to progressive HARDENING of the barrel at the throat due to those same high temperatures, pressures, and the presence of the very gases which lead to hardening and embrittlement of the steel. The stresses and strains on the barrel at each firing then cause the hardened layer of steel to crack and flake-off, leading to loss of material at the throat, and, eventually, loss of accuracy sufficient to cause the barrel to be replaced. An eroded and worn barrel looks, at the throat, rather like the hide of an alligator - the erosion progresses further and further down the bore, while the diameter of the eroded portion at the rear becomes ever larger. It is also true that a barrel worn-out at the throat, and so inaccurate, may be essentially unchanged further down the bore, but AR barrels cannot typically be set-back, re-chambered and returned to use, due to the external contours and pre-existing gas port.
mhb - Mike
Mike, I'm kind of curious regarding your comment about stainess steel barrels having a better bore finish than a chrome moly barrel. My experience with mechanical parts is that stainless steel parts have a rougher finish than chrome nmoly parts. Stailess steels don't machine real well so the finish is often somewhat rough. A friend who attended the S&W armorers school once told me that at the school he was told that it takes 3 times more machining time to make a stainless steel part as smooth as a carbon steel part. We both know that a manufacturer will not invest in that much machining - they will accept the fact that stainless steel will not be as smooth as other materials. I see the big advantage to stainless steel is its corrosion resistance and frequently (depending on the grade) its improved high temperature performance. Rick
When I used to to install production machinery, we always used stainless sheet or "dimple plate" for parts "slides" because it is so much smoother and long wearing than carbon sheet steel . I know the alloys are different from those of gun barrels but I think the wear characteristics are similar. My next AR will have a stainless barrel.
Rider, Parts slides and wear plates are frequenlty made of stainless steel due to the fact that stainless steel is corrosion resistant and coatings on carbon steel wear our quickly leaving bare carbon steel which can corrode - leaving a pitted surface. Rick
The stainless I'm referring to is probably the most commonly used in barrelmaking: 416R - the 'R' stands for 'resulphurized', and this is a steel designed for easy machinability, which has the desired physicals for rifle barrel manufacture, yet is relatively easily machined (as compared to the usual C-M steels in the 4140 series) - and yields better average surface finish when machined with the same tools.
There are other stainless steels which are used in barrelmaking (some 17-4 PH variants, for example), and some of those are, indeed, harder to machine, but are less commonly used precisely because they are more difficult to work, more expensive, and do not really produce longer service life, better accuracy, or any other real advantage I am aware of, some fairly extravagant makers' claims to the contrary notwithstanding.
mhb - Mike
Last edited by mhb; 03-12-2011 at 03:38.
Mike, Thanks for the information. I'll have to do a little research on 416R stainless steel. I must admit that I'm not familiar with this material. You mentioned 4140 steel which is one of my favorite steels for test fixtures - it 416R is more easily machined and yeilds a better surface finish than 4140, it is indeed an excelllent material. Rick
Rick, we used stainless for parts slides and wearplates (same function) because it's harder, smoother and more wear resistant than carbon sheet (mild) steel. I've seen 12 and 10ga steel literally wear through in less than a year from having parts skid over it. Since these slides were indoors and drenched with oil 24/7, corrosion was not an issue.
Originally Posted by rickgman
Last edited by rider; 03-12-2011 at 05:43.
Rider, Anyone who attempts to use low carbon steel for part slides and wearplates deserves a good head slap. Low carbon steel has poor wear resistance and can easily be damaged by the edges of parts. It is a totally different matter if medium carbon steel is used. As you stated, stainless steel will do the trick, too, and in cases where there is an absence of oil, stainless steel also has good corrosion resistance. I do not enjoy the machinability of most stainless steels, however. It can be kind of hard on tools. Rick