Chrome Lined VS Not

[jackblack73]

That chart is not in MOA.

[SomeOtherGuy]

I'm a little dubious that there's any chrome lined barrel that consistently shoots 1 MOA, and I'm a lot dubious that it's a regular occurrence.

Actually not uncommon. Others have posted some results. I'll add the FN SPR, a .308 bolt-action rifle which uses a chrome lined CHF barrel, shoots 1 MOA or less out of the box (with suitable ammo), and has/had the FBI contract for sniper rifles.

As a very general rule an unlined barrel (including a nitride-treated one) has the potential for better accuracy than a chrome-lined barrel. But this only holds when comparing high quality barrels, and in the AR world the junk barrels are generally unlined, and most companies that bother to do chrome lining produce at least OK barrels, while some of them produce excellent barrels. The overall quality of the barrel manufacture is far more important than whether it was chrome lined or not.

[MistWolf]

Something tells me those were actually 3 shot groups...

You should read the threads I linked to and educate yourself, particularly on the difference between Extreme Spread and Mean Radius.

Stop swerving out of your lane

[HansTheHobbit]

That chart is not in MOA.

Ah, right you are. I'm not even going to pretend to understand the math involved in calculating mean radius, but according to people smarter than me group size is typically four times mean radius.

So those groups were actually about 1.5-2 MOA, which is what I would expect from a high quality chrome lined barrel. Like I said before, I'm extremely dubious that a 1 MOA chrome lined barrel exists.

[SomeOtherGuy]

Something tells me those were actually 3 shot groups...

Seriously, people dream of groups that small, and they're using 700 dollar stainless barrels with handloads. There's a big difference between smallest group ever and consistent group size. If you cherry pick which groups you want to publish, then yea, getting sub .5 MOA out of a chrome lined barrel is possible. But I would bet money that it's not consistent, or even repeatable.

Those were not 3-shot groups, the numbers are a MEAN RADIUS from 30-shot groups. The person who did the test, Molon, is meticulous and credible. The numbers do not mean that ALL shots were inside of .4" or whatever, it means that the average error from POA is that amount. Some impacts might be 2" away, while many might be .25" away. Mean radius testing is a more meaningful evaluation of precision than cherry picking one's best groups, whether they are 3, 5, or 10-shot groups. It produces smaller numbers, which is not misleading, it's just a matter of understanding what the number means.

This reminds me of a recent article in shotgun news where they claimed to get .5 MOA out of a SCAR 16 with factory ammunition. .5 MOA out of a piston gun with a pencil chrome lined barrel? I almost fell off the toilet I was laughing so hard.

People don't always use " x MOA" in the same way, so it's hard to know if that claim is plausible or not. If it's intended in the casual way of "my group was 1/2" at 100 yards so it's 0.5 MOA" then it sounds unlikely, except maybe as a single lucky-best group of many. But this isn't relevant to Molon's test results or the general accuracy potential of a chrome-lined barrel.

[HansTheHobbit]

Yea, I get it. I should have looked closer.

But in my defense, I didn't take into account that mistwolf would post data proving my original statement. All I said was that chrome lined barrels aren't as accurate as non chrome lined barrels and that I doubted the existence of MOA chrome lined barrels. Looks like the data he posted pretty much backs that up.

[MistWolf]

Yea, I get it. I should have looked closer.

But in my defense, I didn't take into account that mistwolf would post data proving my original statement. All I said was that chrome lined barrels aren't as accurate as non chrome lined barrels and that I doubted the existence of MOA chrome lined barrels. Looks like the data he posted pretty much backs that up.

Again, you do not understand. The SOCOM barrel produced a Mean Radius of .35". It's Extreme Spread is .9". An ES of .9" is less than 1 MOA.

MR is approximately one third of ES, depending on group shape. There will be a greater difference between MR and ES if the shot are strung out instead of round. If you do your math correctly, you'll see that the Colt barrels Molon tested, which are all chrome lined, have an MR that falls between .32 and .58. That will be an ES of approximately 1.0 and 1.8 which does not back up your claim that consistently 1 MOA chrome lined barrels do not exist. Technology for precision hard chrome lining has come a long way

[bill530]

I saw that davidsons is offering a pinned 14.5 inch Expanse with what they say in the description is a " chrome lined amd heavy profile". In the picture it has the m4 step in the barrel. Do you guys think that could possibly be a 'm4a1 socom barrel? Im not considering buying one. Just curious.

[HansTheHobbit]

Again, you do not understand. The SOCOM barrel produced a Mean Radius of .35". It's Extreme Spread is .9". An ES of .9" is less than 1 MOA.

MR is approximately one third of ES, depending on group shape. There will be a greater difference between MR and ES if the shot are strung out instead of round. If you do your math correctly, you'll see that the Colt barrels Molon tested, which are all chrome lined, have an MR that falls between .32 and .58. That will be an ES of approximately 1.0 and 1.8 which does not back up your claim that consistently 1 MOA chrome lined barrels do not exist. Technology for precision hard chrome lining has come a long way

No, I said I was dubious as to whether there was a consistent MOA chrome lined barrel. I did not claim they do not exist, just that I'm skeptical, and I still am. I've heard four times mean radius equals extreme spread, but like you pointed out there's no exact formula to calculate that, so we don't really know for sure either way what the actual group sizes were without seeing the actual groups.

Another thing I'm wondering is how many barrels they had to test before finding ones that accurate, and what ammo was involved. If you take the best of the lot, then develop handloads for them then anything is probably possible. What I'm saying is I doubt that you can take a lot of Colt M4A1s and get 1 MOA out of them, even if you were to free float the barrels and use match grade factory ammo.

Plus, the only barrels that did 1 MOA were heavy profile, while the more average profiles were more in the 2 MOA range. So really what we're saying here is that if you give a chrome lined barrel every chance of success then you can just barely squeeze 1 MOA out of it. That, in my opinion, isn't really something to write home about. I will concede that it looks like it's probably possible to squeeze 1 MOA out of the best possible scenario for a chrome lined barrel. I will also concede that chrome lined barrels are probably getting more accurate. I've read recently that there have been advancements made in tooling that can produce CMV barrels on par with stainless, and while I doubt that's really a fair statement, I'm willing to accept that today's chrome lined barrels are probably better than those of ten or twenty years ago.

At the end of the day, however, I firmly believe it still stands that chrome lined barrels do not have as much accuracy potential as non chrome lined ones. I've heard that chrome lining opens groups by about .25'', and that appears to be more or less accurate as far as I can tell.

ETA: What would have been a more useful test is if they had taken two barrels made by the same manufacturer, same profile, same chamber, etc. and had one chrome lined and left the other in the white. If that test were done and shown to be repeatable, then that would be something to write home about.

[P2000]

Rather than trying to use math to convert a mean radius measurement to extreme spread, extreme spread should be punched in the nuts and abandoned.

Mean radius paired with a 10 shot or greater group is far more relevant for evaluating the precision of a rifle.
Hans you really should read up on mean radius. Molon has plenty of posts, pictures, diagrams, info on how the military tests their ammo (they call mean radius AMR). I made a post a while back as well talking about 10 shot groups and mean radius.

Sent from my XT1565 using Tapatalk