ovenpaa wrote:The issues with machining LW barrels seems to be fuelled as much by rumour as direct experience, I have special steel LW barrel due in soon and will be using a 'normal' reamer to chamber it.
David,
Absolutely.
I have once chambered 30 LW barrels in one run....and the same reamer still works fine 20 years afrer....
Hereunder extract from a recent post:
R.G.C
The LW barrels have an excellent reputation in Europe and at Bisley in particular.
They do not interest gunplumbers as they require a little more care and skill than the free machining 416 and mostly last longer…..
Hard on reamers could be only a point if reamers are simple HSS and not HSS+Co.
Hereunder an extract of a document I wrote some time ago on barrel steels.
I point I have no interests in the LM business…
R.G.C
-1°--Starting from the material :
Except one european manufacturer, for corrosion-resistant steel (the term Stainless is inadequate for the 400 series steels), all uses the same alloy, and it is the AISI/ASTM/SAE 416R (Euronorm X12CrS13 or Werkstoff Nr 1.4005).
Barrelmakers may say theirs are ultra-sonic tested, aircraft quality, quality certified….., it remain the same metal, as made by a few plants worldwide. Might be sold eventually under multiple labels and trade names, the physical, chemical and mechanical properties remain exactly those of the same alloy closely defined jn the norms.
This metal is the barrel makers preferred, not for its qualities as barrel steel, but for its machine-ability, as alloyed with sulphur. A blessing for the machinists, but on the detriment of the qualities one should normally expect from a barrel: Quite soft, limited friction capacity, prone to internal hollow corrosion… But it polishes so well and easily that the shine of it attracts at first..
One large (the largest In Europe in terms of target barrels) barrelmaker, Lothar Walther in Germany, uses a different alloy, AISI 420 (EuroNorm X20Cr13 or W/Nr 1.4021), slightly higher in Carbon content (0,20% as to 0;12% of the 416) and in Chromium (13% as to 12% of the 416), but no sulphur addition, and which possess all the properties one could ask for such a purpose. Walther’s primary business is deep bore drilling to the closest tolerances, and they master this process over many decades and 3 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 is certainly worth the effort. Does this makes a better shooting barrel? Certainly not, but longer lasting no doubt the answer is ‘yes’….
-The 416, supplied in annealed condition, is about:
Brinell Hardness : 170
Rm: 630MPa
Modulus of Elasticity: 200GPa
Thermal conductivity: 25W/m-k
-While the 420 is:
Brinell Hardness 205
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 the same alloy specifications and under same supply Q.C and traceability conditions.
The Walther 420 is supplied by Boehler-Udderlohn from Austira under Walther’s specifications.
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 to the 420 to a lesser extend.
-A typical brand is:
Brinnell hardness: 225 to 241
Rm: 1000MPa
Modulus of elasticity: 205GPa
Thermal conductivity: 43W/m-K
This alloy is harder than 416, have a lesser friction coefficient and much better thermal conductivity (important). It is however much less favoured despite the above superiorities..
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R.G.C.