Considering First AR-15

Jeez, man, I registered just to tell you this:

http://www.bushmaster.com/shopping/barrel-assemblies/

They will build an AR any way you want it. Simply take your pick of barrel and tell them you want that.

Specifically I'm referring to "Superlight 16" barrel" and the "M16 Government Type Profile 20" bbl". But there's others too.

As for BM, they have the best overall QC according to the hundreds of posts I read every day at www.ar15.com. They do have problems from time to time, like somebody in their factory overtorquing barrels, but any other company will have problems too. BM will fix anything, and fast, if you just let them know.

Edited to add that you should read all the posts you can at www.ar15.com, specifically the 'build it yourself', 'maintenance and cleaning', and 'troubleshooting' forums. There's a lot of info there!
 
That's what I get for posting at 4 am.

Harder will wear slower, yes, in the same alloy, which these are, close enough. It may also fracture more easily, depending on the specific heat treat used. 41XX steels are NOT high-shock steels like the S series.

Again, barrels don't need to be particularly hard, but resilient and tough.

Note that titanium, which is VERY hard and strong, is brittle as hell and not wear-resistant.

Again, I'm not a metallurgist, but the steels are marketed to the trade as mechanically identical. So why pay extra? First find out what advantage, if any, it offers, then what tradeoffs there are, then the difference in cost for a value-based estimate.

The most ludicrous one I ever saw was a maker of fantasy knives using "the same steel used in nuclear reactors" for his blades.

Now, to the layman, it may sound like it's godawful strong and resists millions of degrees...

...in reality, a reactor is a boiler. It requires something non-reactive to avoid contamination.

So they use 316 SS, same as is used in commercial kitchens and kitchen sinks. Holds an edge about as well as lead.

But is sure SOUNDS nifty.
 
I've been looking for a description of the barrel steel requirement in the tech library, but so far haven't found it - I may never be able to.

This 60+ page document is the M16A2 "Mil-Spec" - actually MIL-R-63997 - for anyone who wants to get involved. Open it with Adobe Acrobat. It doesn't include barrel steel. It does include other MIL descriptions and titles.
http://astimage.daps.dla.mil/quicksearch/basic_profile.cfm?ident_number=31489
If this link doesn't paste right, go to the following link and search for "MIL-R-63997".

You can search them from is this site, which has about 100,000 mil specs and drawings:
http://astimage.daps.dla.mil/quicksearch/

bOne, thanks. I hadn't spent much time at BM's "Barrels and Assemblies" page, since I wanted a complete rifle the first time. That's a good source, though. I have spent some time at AR15.com, but obviously not enough time looking for reports of malfunctions.

Jaywalker
 
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If you haven't yet, check out The Maryland AR-15 Shooter's Site, it has reams of information.

4150 is mil-spec but 4140 is apparently pretty close but slightly softer. Can't say how that translates into long term wear but Shooting Times recently did a test of a Colt National Match AR-15 set-up (4150 steel, no chrome lining) where they fired 10,000 rounds in two days (cleaning every 1,000 rounds and allowing cool down time when barrel began smoking). The barrel began to show enough throat erosion that the PMC test ammo was keyholing around 9,000+ rounds. They switched to Hornady softpoint (where the ogive was different and didn't wear at the same spot) and finished the test.

Troy, a moderator at AR15.com reports 7000 rounds with no cleaning through his Bushy.
 
What I meant to say is, they will build a complete rifle in any configuration you want; if you pick, for example, the government profile 20" bbl and tell them you want that, they'll put it on and you get a complete rifle set up with what you want on it. But that means you'd have to order it from them, or have your dealer order it like that. Usually costs more than just picking a rifle off the dealer's rack.

But if you bought yours already, Kurt of KKF does a real good job of turning down barrels, I hear. Haven't sent anything to him myself, though.

Good luck with your rifle. Soon you will start feeling the urge to get a bunch of different uppers...
 
I located the MilSpec of the small arms barrels at:
http://assist.daps.mil/eAccess/index.cfm?ident_number=25134

That doesn't paste well, so type "MIL-S-46047" at http://astimage.daps.dla.mil/quicksearch/ .

Unfortunately, I don't know exactly what it means. I found that there are different MilSpecs for each class of weapon; the M2, for instance, is different than the M16.

They don't, at least in this document, specify commercial equivalent nomenclature - there's no mention of "4140" or "4150." Instead, they require a level of steel "performance" and composition.

I'm sure madmike is right regarding the content of 4140, and that is almost exactly the requirement for M16 barrels. There is, though, a difference in required molybdenum at .55-.70, vice 4140's .15-.25, and possibly in hardness.

Hardness is a little more difficult for a non-metallugist to say, because they might be measuring it differently, in size or scale, and there also appear to be tests for impact resistence when hardened well below its finished hardness (35 HRC(Rockwell C ?)). They both seem to refer to barrel-sized billets, though, and the required figure is "54 HRC" (Rockwell C ?),while 4140 typical hardening is "44 - 50." That seems to indicate that, at least for M16 barrels, 4150 has the edge.

We'll need a metallugist to give us the real interpretation, I guess. With a chrome-lined barrel and chamber, would anyone ever notice?

Jaywalker
 
I'm learning a lot from this. Thanks.

The steel specs are likely newer than last time I checked. A friend of mine, now dead, was a machinist at the contractor building 50s locally.

And old .45s are 4140, also.

Well, if that's the new standard, then by all means get it in your AR.
 
{pulled from another one of my posts, but for a suitable occasion}

A new person to jump on the AR-15 bandwagon. Isn't life grand! Good luck with whatever you get, but remember this, you can always trade stuff out if you don't like it, or it gets old, or whatever. That is what makes AR's so great. After some swapping around, here is what I have come up with:

Top gun:
-- Bushmaster Y2K Limited Edition lower
-- DPMS A# flattop upper free floated HBAR w/ slipover
-- Tactical latch
-- Hogue grip
-- Cheap rings and scope

Bottom gun:
-- Pre-ban Oly Arms lower
-- Bushmaster collapsible stock
-- FN upper
-- Wilson Hbar
-- Leepers dual-stage sight rail
-- Tasco Aimpoint PDP3 red dot scope
-- M3 Tactical Illuminator
-- Laser
-- Extended flash suppressor

ar_15%20collage.jpg
 
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