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Posted: 1/12/2006 8:52:57 AM EDT
Does LMT make heavy barrels that are available for us civilians to buy?? If so, where??
Link Posted: 1/12/2006 8:58:47 AM EDT
I asked the same question yesterday of a LMT dealer and he said no. They show them on the website though.
Link Posted: 1/12/2006 9:03:15 AM EDT
[Last Edit: 1/12/2006 9:06:31 AM EDT by mr_wilson]
FYI, CMMG sells quality heavy barrels, no they ain't LMT, but their good ones of spec. 4150 steel.

Mike

E.T.A. - link: www.ar15.com/forums/topic.html?b=7&f=22&t=307921
Link Posted: 1/12/2006 9:06:45 AM EDT

Originally Posted By mr_wilson:
FYI, CMMG sells quality heavy barrels, no they ain't LMT, but their good ones of spec. 4150 steel.

Mike



Yea, I'm actually debating right now between a 16" LMT or CMMG. I think I have to do a little more research before I settle on something..
Link Posted: 1/12/2006 9:07:25 AM EDT
[Last Edit: 1/12/2006 9:08:00 AM EDT by BravoCompanyUSA]
Link Posted: 1/12/2006 9:11:23 AM EDT
Paul above at Bravo may also be able to fit your bill, as I just bought a sweet BCM upper off him the other day, (no it ain't a heavy barrel just a standard M4 type).

Both are excellent dealers with great service and I own products from both....

Mike
Link Posted: 1/12/2006 1:04:12 PM EDT
Paul is correct. The picture was of a MRP.
Link Posted: 1/12/2006 1:48:11 PM EDT

Originally Posted By mr_wilson:
FYI, CMMG sells quality heavy barrels, no they ain't LMT, but their good ones of spec. 4150 steel.

Mike

E.T.A. - link: www.ar15.com/forums/topic.html?b=7&f=22&t=307921



I wonder if the 4150 kool aid drinkers can explain, using metallurgical specifics, why 4150 is so "good"............
Link Posted: 1/13/2006 2:36:58 AM EDT
[Last Edit: 1/13/2006 3:12:58 AM EDT by mr_wilson]

Originally Posted By SWO_daddy:

Originally Posted By mr_wilson:
FYI, CMMG sells quality heavy barrels, no they ain't LMT, but their good ones of spec. 4150 steel.

Mike

E.T.A. - link: www.ar15.com/forums/topic.html?b=7&f=22&t=307921



I wonder if the 4150 kool aid drinkers can explain, using metallurgical specifics, why 4150 is so "good"............



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


Originally posted by Hoplophile:
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




Originally posted by Hopophile:


Originally Posted By mh454:
Good info Hopophile. So if they are so close to each other then where did this theory of 4150 handling heat better come from?



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.




Here are some older threads, ya may be interested in, (same subject):

archive.ar15.com/forums/topic.html?b=2&f=27&t=138126

archive.ar15.com/forums/topic.html?b=6&f=2&t=151785

archive.ar15.com/forums/topic.html?b=3&f=12&t=167129
Link Posted: 1/13/2006 4:34:54 AM EDT

Originally Posted By mr_wilson:

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



Try to think of it as two numbers - the first two digits are the type of alloy steel, the second two digits are percent of carbon. You can see the 4140 has 0.38 - 0.43 % carbon, and the 4150 has 0.48 - 0.53% carbon.

Carbon content affects the hardness and ductility of the final product. The difference in these two is really pretty negligible.
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