Well, I would say that which is “easier” (between chromo and 416) has a lot to do with the experience and preference of the machine operator, as well as what type of machine is being used – but yes, many will say that they prefer to work with 416 vice 4150…
…but that is not what I said.
I maybe should make it clearer though: Metals are (loosely) rated with a “machinability rating” – and the base for this rating (1.0) is free machining carbon steel, alloys can be much lower on the scale, right off the top of my head, I think that 41XX is down around .50-.60 and 416R is well above that in the .80s?
But, as this is a primer, I just thought I would make the general statement that 416 machines nearly as well as carbon steel, rather than say that it has a rating of .85 (or whatever)… then we are off on free machining additives and resulfurization, chip control, inclusions and break points, and then the door is opened to the dreaded sulfur stringers and then night of the living sulfur stringers and then…
Well, I would say that which is “easier” (between chromo and 416) has a lot to do with the experience and preference of the machine operator, as well as what type of machine is being used – but yes, many will say that they prefer to work with 416 vice 4150…
…but that is not what I said.
I maybe should make it clearer though: Metals are (loosely) rated with a “machinability rating” – and the base for this rating (1.0) is free machining carbon steel, alloys can be much lower on the scale, right off the top of my head, I think that 41XX is down around .50-.60 and 416R is well above that in the .80s?
But, as this is a primer, I just thought I would make the general statement that 416 machines nearly as well as carbon steel, rather than say that it has a rating of .85 (or whatever)… then we are off on free machining additives and resulfurization, chip control, inclusions and break points, and then the door is opened to the dreaded sulfur stringers and then night of the living sulfur stringers and then…
Kino, are we not on the same page? Based on your own machinability numbers, 416 is clearly the easier of the two (meaning 416 compared to chromoly) to machine at similar hardness. Barrels aren’t made from low carbon free machining steel so it really isn’t relevant to compare it to 416R.
For those that don’t know…
The American Iron and Steel Institute ran tests for machinability using AISI B1112 at 160 Brinell (a free machining low carbon steel) being turned at 180 surface feet and compared it to other materials. Its performance (set at 100%) is the basis for the ratings of other metals. Those materials with a rating of less than 100% are more difficult to machine. Those with a rating of over 100% are easier to machine.
4140/4150 chromoly steel has a machinability rating of approximately .32 to .52 depending on hardness. But 416 is a free machining martensitic stainless and has a rating of anywhere from .24 to .88 depending on hardness.
For comparison, Inconel is around .12, 7075 aluminum runs anywhere from approximately 3.2 to 4.8.
Awesome post. Everything you wanted to know about barrels but were afraid to ask.:eek:
I too would like to see some discussion about breaking in a barrel. I remember what Gale McMillan wrote on The High Road a few years back, but his opinion seemed to be a minority viewpoint.
So from what I’ve read, Colt, LMT, CMT, BCM and the upper end (true mil-spec) manufacturers use 4150 and the more civilian recognized manufacturers like RRA, DPMS, Bushmaster, etc. use 4140? Just curious.
I figure most of the 1/9 twist barrels will be the 4140, but as I’ve stated in other posts, I’m a tech junkie and “just want to know”. Also, alot of folks use “Wilson” (Wilson arms) heavy match barrels and E.R. Shaw “heavy match” barrels, I assume they are mostly 4140 when supplied to RRA, DPMS, Model 1, etc unless they are the 416 SS???
Great post, very informative. Thanks for your time input into it.
I understand how it is made, question is what should I expect from two identical carbines where one has 1/7 and another has 1/9 twist? If nothing then why some manufacturers adopt 1/9 while other 1/7?
Well it depends on several things. For instance, a 1/7 twist barrel shoots 55gr ammo very well to about 100yds. Past that we see the groups open up a lot. Same with the 1/9 twist barrels. At about 100yds, 75/77gr ammo does pretty well, but as you go farther out, your group sizes can open up.
So if you want to shoot heavier grain bullets at distances over 100yds, stick with a 1/7 twist barrel (which is what I shoot).
Thanks, that makes sense. I’m not planning to go long with the carbine and will be looking at .308 for that purpose some time later (and that opens another set of questions but probably for a different board :))
[light-hearted jab made in jest] And finished, too.[/light-hearted jab]
Those are very interesting articles. I’d like to track down the other articles in the series. Thank you for posting those up.
A few months ago I researched barrels for my first build project. I scoured the Internet almost daily for several months before finally making a decision. Even though my research led me to M4C numerous times - sometimes to threads I had already visited several times - I never recall seeing this thread. I think I can work The Google pretty well, and thought my search terms within applicable topics were widely varied. Dang. My own process could have been much simpler if I had only discovered this thread first.
Would it be an exaggeration to suggest that the steels that are easiest to rifle by single-point cutters and broaches are also the fastest to wear out from use? The introduction of button rifling and then cold-hammer forged rifling offered the ability to economically rifle harder steels.
The ironic thing is that several Fudd rifle companies were using CHF barrels nearly four decades ago. Back in February 1971, “American Rifleman” ran the second of a three-part article by Jac Weller on the construction techniques used by US firearm manufacturers. Remington, Ruger, Weatherby, and Winchester were all cited as using CHF barrels for at least some calibers and models.
According to Roy Weatherby’s biography, he was using CHF barrels in his Mark V rifles as early as 1959. (They were made by Sauer at the time.)
In his 1977 book “American Rifle Design and Performance”, L.R. Wallack noted that Winchester was still producing CHF barrels, and their representatives had even claimed that they were the only major sporting arm manufacturer to chamber their barrels in the same process.
