Quoted:
I wonder if the 4150 kool aid drinkers can explain, using metallurgical specifics, why 4150 is so "good"............
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Often wondered that myself...., although it's difficult to go back 3 or 4 years to the OLD debates and pull one up for ya, (oops, guess not as hard as I thought, since the Archive server works good now, see below). Sufficed to say the "experts" seemed to think that in "chrome-lined", military styled, SHTF type rifle having a "MIL-SPEC" 4150 barrel was preferable to the 4140 barrels being sold by DPMS and others.
I ain't no metallurgist and simply read their comments, of-course back then most all my AR15s were 1/9 twist whereas nowdays I have 4 - 1/7s (all 4150) and only my CR6724 long range stick is still 1/9 (stainless steel).
They did have some fairly technical and involved debates over than subject and I can tell ya the 4150 crowd convinced me and won the debate IMO, hope this helps.
Mike
E.T.A - here's what I found perusing the Archive server:
from this thread:
archive.ar15.com/forums/topic.html?b=3&f=118&t=181565 Quoted: 4140 - Chemistry (%): Carbon 0.38 - 0.43 Chromium 0.8 - 1.1 Iron Balance Manganese 0.75 - 1 Molybdenum 0.15 - 0.25 Phosphorus 0.035 max Silicon 0.15 - 0.35 Sulphur o.04 max Physical Properties: Density (lb / cu. in.) 0.28 Specific Gravity 7.83 Specific Heat (Btu/lb/Deg F - [32-212 Deg F]) 0.114 Melting Point (Deg F) 2580 Thermal Conductivity 23 Mean Coeff Thermal Expansion 7 Modulus of Elasticity Tension 33
4150 - Chemsitry (%): Carbon 0.48 - 0.53 Chromium 0.8 - 1.1 Iron Balance Manganese 0.75 - 1 Molybdenum 0.15 - 0.25 Phosphorus 0.035 max Silicon 0.15 - 0.35 Sulphur 0.04 max Phystical Properties: Density (lb / cu. in.) 0.284 Specific Gravity 7.8 Specific Heat (Btu/lb/Deg F - [32-212 Deg F]) 0.113 Melting Point (Deg F) 2600 Thermal Conductivity 23 Mean Coeff Thermal Expansion 7 Modulus of Elasticity Tension 30
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Quoted:
Quoted: Good info Hopophile. So if they are so close to each other then where did this theory of 4150 handling heat better come from?
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There are some differences in specific heat and melting point, even if they are small. Bascially the difference is that the military requires 4150, and some places save a little money by using 4140.
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Here are some older threads, ya may be interested in, (same subject):
archive.ar15.com/forums/topic.html?b=2&f=27&t=138126archive.ar15.com/forums/topic.html?b=6&f=2&t=151785archive.ar15.com/forums/topic.html?b=3&f=12&t=167129