c-g-designs

BARREL STEELS “DIFFERENCES”.

Except one manufacturer, for corrosion-resistant steel (the term Stainless is inadequate here), all uses the same steel, and it is the416+S (Euronorm X12CrS13 or Wk Nr 1.4005).

Barrelmakers may say theirs is ultra-sonic tested, Aircraft quality, Quality certified….., it remain the same metal, as made by a few plants worldwide. Might be sold eventually under different labels and trade names, the physical mechanical and chemical properties remain those of the same alloy.

This metal is the preferred for its machine-ability, as alloyed with sulphur. A blessing for the machinists, but on the detriment of the qualities one could normally expect from a barrel: Quite soft, poor friction coefficient, prone to hollow  (pit or cave) corrosion… But it polishes so well and easily that the shine of it attracts at first..

One large (and probably the largest in terms of target barrels)  barrelmaker, Lothar Walther in Germany, uses a different alloy, AISI 420 (EuroNorm X20Cr13 or Wk Nr 1.4021), slightly higher in Carbon content (0,20% as to 0,12% for the 416) and in Chromium (13% as to 12%), but no sulphur addition, which possess all the properties one could ask for such a purpose. Walther’s primary business is deep bore drilling, and they master this process since several generations.   

Their ‘savoir-faire” is unique, and they are the only capable of using industrially this alloy. It might well be not too much liked by those who have to machine it afterwards for chambering and threading, but, quality-wise, the result and durability are certainly worth the effort…Not a challenge for a competent machinist.

-The 416, supplied in annealed condition, is about:

          -Brinell Hardness : 170-175HB.

          -Rm: 630-650MPa.

          -Modulus of Elasticity: 200Gpa.

          -Thermal conductivity: 25W/m-k.                                                                                                   

    -While the 420 is:

          -Brinell Hardness 205HB.

          -Rm: 725Mpa.

          -Modulus of Elasticity: 200GPa.

          -Thermal conductivity: 25W/m-k.                                                                         

-At least one mill (Crucible) claims having a specific brand of 416 for barrels, but others, at least 2 in USA and 3 in Europe, are offering exactly the same material and under exactly the same alloy specifications and under same supply conditions.

The Walther 420 is supplied by Boehler-Udderlohn  from Austira under Walther’s specifications who mostly concerns straightness.

Just a quick mention here of the CrMo steels used for barrels . The various alloys used are all of higher mechanical and physical properties than the 416 and even the 420.  To note is hardness, better friction coefficient and thermal conductivity.

-A typical one is:

          -Brinnell hardness: 225 to 241HB.

          -Rm: 1000MPa.

          -Modulus of elasticity: 205GPa.

          -Thermal conductivity: 43W/m-k .

  Barrels made from CrMo alloys are perhaps not better shooters than 416 and even 420,  but, from material considerations, they have the potential to be such,with no doubt increased accuracy life.

The superior thar mal conductivity is also an element to consider.

R.G.