Why is 4150 steel better?

[Mjolnir]

"... I shoot for fun, and even manage to enjoy it at times, but a some of the items in the toy box aren't toys all the time. Thankfully, rarely are they asked to do more than resist corrosion and stay assembled, even when they are being carried. That said, they aren't any more than dead weight if they can't perform under the worst conditions I can plan for, so, at least for these few non-toys, I try my best to buy the best.

If, however, the denizens of that evil lord with whom you wage constant war are no more than pop cans and occasional bits of offensively arranged geometry, there is no real need to look beyond financial logic and safety when choosing such materials. That doesn't mean you shouldn't buy the better barrel, it just means that going with a cheaper barrel will leave you at worst with an unholy pop can.

The question is, do you want it? If you do want it, the little question of need shouldn't stop you from spending your money on what you want. I've got lots of crap I don't need, and I enjoy all of it."

CLASSIC!

[rsilvers]

"The Chart" lists CMMG barrels as "Milspec". Does this mean these barrels are 4150 CMV? It was my understanding they were 4150, but not CMV?

I assume that 4150 NON-CMV is still "better" than 4140? Or do I have this all wrong???

There are non-CMV 4150s which are mil-spec, but they need to match the specific chemical properties outlined in the document.

[rsilvers]

Interesting to note that, despite the fact that 4140 is agreed by all to be the weaker steel when rapidly heated under sustained firing, there does not appear to be a single maker that sells a 4140 barrel that also MPIs and HPTs every single sample of their barrels.

This is because 4150 is more susceptible to cracking than 4140 during heat-treat and so 4150 is more likely to fail and therefore warrants more testing. The other reason is that companies that use the mil standard 11595 steels are trying to meet a mil-spec, and so they are more likely to also do the testing that is specified.

It should be noted that HK and Swiss Arms (Sig 550 series) - which I assume we all agree are very durable barrels, do not meet 11595 mil-spec for barrel steels. In other words - there are other ways to make an ultra-premium barrel than to follow the current US govt. minimum standards and Bushmaster and Remington are doing so with the ACR.

The main difference between 4140 and 4150 is that 4150 has more carbon so that it can be heat treated to a higher hardness/strength. However, no one heat-treats barrels to MAX hardness because they would get too brittle. 4140 can be heat-treated to a hardness/strength greater than what is ever done with 4150 or 4150 CMV barrels. At any given Rockwell value, 4150 tends to have more tensile strength but less yield strength and toughness/impact resistance than 4140. Which is more important to a barrel? Well, it depends on your criteria. If you want the barrel to pass a 'stuck bullet' test and not rupture if a second bullet is fired, then 4140 may do better. And then combine this this added toughness of 4140 with the right lining, be it cobalt alloy, what Swiss Arms does, what the ACR does, etc - and it could easily outlast a 4150 CMV Colt barrel.

[brad100]

And socom is asking for next better now!!
And, have u seen real heavy 14.5
Make unreal 1000 yard hits, its a tough barrel, none perfict, but troops should have the best, I been doing ar stuff since the year 1970 somthing,
Now, kids are building armchair lego guns and blocks, not one of these parts whores were around long ago, lmt was
And a colt vender, i found on the telephone, lol
Now the crap thats out there and loved because it works is sad...
Colt and FN build real stuff, every part checked, and ill tell u, the hardening on colt trigger group parts is so noticable
In sure FN and LMT are also
Ive helped on hundreds of projects, and the hammer and pins are a joke,
I always find real military, make it legal and only use that

Wont use parts whores crap!!

Do what u like, ive never, ever had a rifle fail, and ive shot 2000 russian steels on a sat!!
With evel coatings, pure bull shit about them...

Ok, ill stop, Anti Lego. Lol

Brad

[JSantoro]

Each and every post on this forum has a date-stamp in the upper-left corner; pay attention to them when browsing.

Do not revival-post a 6yr-old thread unless you can add new info or ask new questions.

An impaired ramble of random info is neither of those things, and necrophilia isn't cool.