Barrel Accuracy

[Press Check]

What makes one modern barrel more accurate than another? Put a good shooter behind two barrels, why does one shoot a minute, and the other shoots 3 minutes.

Case in point, I have a Colt SOCOM upper that easily shoots a minute, and a BCM SOCOM upper than shoots 3-4 minutes at the same distance, with the same ammunition, under the same conditions.

In the case of both of those barrels in particular, I assume we're talking about the same materials used, the same manufacturing process, etc., so where's the difference?

[markm]

Is the BCM button rifled or hammer forged? Buttons wear out. And steel can have flaws that create uneven bore diameter down the pipe.

Pin gauging is a good way to tell if a barrel is problematic. That and/or bore scoping.

[sig1473]

Is the BCM button rifled or hammer forged? Buttons wear out. And steel can have flaws that create uneven bore diameter down the pipe.

Pin gauging is a good way to tell if a barrel is problematic. That and/or bore scoping.


BCM only makes the SOCOM profile in 14.5" and 16" standard rifled.

[markm]

So the normal button rifle gamble applies. Plus the chrome lining process... If a barrel won't shoot 77gr OTMs well at some point after a break in, I'd see about bore scoping or pin gauging.

[Stickman]

What makes one modern barrel more accurate than another? Put a good shooter behind two barrels, why does one shoot a minute, and the other shoots 3 minutes.

Case in point, I have a Colt SOCOM upper that easily shoots a minute, and a BCM SOCOM upper than shoots 3-4 minutes at the same distance, with the same ammunition, under the same conditions.

In the case of both of those barrels in particular, I assume we're talking about the same materials used, the same manufacturing process, etc., so where's the difference?



It isn't the same unless it is coming off the same machines with the same wear and tear on equipment. There are plenty of barrels that are 1-7 twist which love one bullet and hate another. Switch to a different barrel in the same twist and that special bullet and load just might not be so special anymore.

[elephantrider]

I'll echo what Stickman posted. There are so many manufacturing variables to barrels, let alone chrome lined barrels, that there is no 'same.' If you want to evaluate each barrel, try the same optics on each barrel/upper, with a variety of ammunition, a la Molon. The difference in accuracy you are seeing, may just be a difference in throating. If you are seeing worse accuracy across the board then the BCM may indeed be a 'lesser' barrel, or have defects, or just less tolerant of a variety of ammunition/loads.

[Clint]

There are many many variables involved and each one has a potential effect on accuracy.

[Rascally]

So basically, each barrel is unique and a law unto itself..?

[Pappabear]

So basically, each barrel is unique and a law unto itself..?

Pretty much. Unless your buying high end precision barrels, it's always a gamble. Your BCM might like 55grain bullets or might not. Still 3 or 4 moa with high quality match ammo is not ideal.

What ammo are you shooting in both guns ?
PB

[17K]

Generally, those Colt SOCOM barrels are very accurate! I shot one for awhile in 2016 and shot one very extensively in 2010-2012.

Both were about .75moa shooters, the last group I shot with the first one was 1.2MOA with a NSN ACOG with MK262, prone on the mag. That barrel had over 15K rounds through it and had been cleaned once!

[Press Check]

What ammo are you shooting in both guns ?
PB

Black Hills, MK262, Mod 1.

[Press Check]

Generally, those Colt SOCOM barrels are very accurate!

Ridiculously, notoriously, predictably, and boringly accurate. ;)

[longshot2000]

I have found that in the shorter barrels, Colt does better than most, in terms of all around goodness of a barrel. Accuracy, wear, ability to take grit and grime. A number of our mil and LE clients have ditched other barrels in favor of Colt in the 10.3" to 14.4" variety, and some are ditched more than others. Daniel Defense seems to run a close 2nd with Gov't profile barrels, in terms of accuracy, in my experience and in working with operators. As you go out to 16, 18 and 20", you are talking about an entirely different gun, and different barrels, and many others do great, and better than the Colt SBRs.

For Chrome-lined barrels, 1.0 MOA is very good. Like Stick and others have said, it really all depends, and you will see people swear by barrels that give much better or much worse results. Remember, though, that a chrome-lined barrel is not built for accuracy. Its purpose is durability. I know I will get detractors, but it is true. The chrome lining is not there to make the barrel accurate. In fact, accuracy and chrome lining are inversely correlated, all other facts remaining the same. Whether it is buttoned or CHF I don't think matters. Buttoning is generally more accurate, but once you introduce chrome lining, that is the single largest factor that will lead to different results, as getting a straight and consistent lining is very difficult.

[HD1911]

In my experience so far, a solid chrome lined barrel in a legit platform, with match ammo, and a good shooter ought to be hold an MOA, or darn close to it. Wether it be an AR15, a SCAR17S, or an LMT MWS.

[17K]

Or an FN SPR.

[ChoppinFatTony]

I have found the 14.5" Colt SOCOM barrels love .77gr OTM Mk262's alot. Whether it was by issued one in 10-11 or my current home built one with it.

Sent from my SM-G920T using Tapatalk

[Pappabear]

Black Hills, MK262, Mod 1.

That should be around MOA if your doing your job, so the barrel is just not up to snuff IMHO. I agree with others on average, very good CL barrels will shoot MOA, I have several.

PB

[ALCOAR]

What makes one modern barrel more accurate than another? Put a good shooter behind two barrels, why does one shoot a minute, and the other shoots 3 minutes.

Case in point, I have a Colt SOCOM upper that easily shoots a minute, and a BCM SOCOM upper than shoots 3-4 minutes at the same distance, with the same ammunition, under the same conditions.

In the case of both of those barrels in particular, I assume we're talking about the same materials used, the same manufacturing process, etc., so where's the difference?

I would have bet heavily on your exact outcome b/t a Colt barrel vs. the comparable BCM barrel. Lots of documented accuracy tests on Colt and BCM barrels, one I almost never read about producing a suspect, or bad performing barrel, the other I read quite often about it's mediocre performance.

I'd expect if you got two of the same Colt barrels, or two of the same BCM barrels and did a more apples to apples evaluation....your results wouldn't suggest that such a universal discrepancy exists from one barrel to the next.


So basically, each barrel is unique and a law unto itself..?

Barrels aren't true snowflakes, but given we understand basic materials & engineering science, we can assume that every barrel can't be exactly identical as the previous one made. Things like tool wear on the drill bits, or reamer are examples of this. Then you could also find subtle differences in lapping and polishing. If the context we're talking about is just comparing one barrel to the next on the same line, from the same mfg., and made one after another, these subtle differences would be microscopic in analysis, and to my knowledge wouldn't lead to the shooter ever noticing a difference on target.


Now in the context of barrel manufacturer to barrel manufacturer, these areas create vast differences b/t two comparable barrels from different manufactures. My Rock 5R SS barrels are built with loving care, and no expense is spared in the pursuit of building a super accurate barrel. Those areas like using only the best machines, constantly changing bits, and spending special attention to the lapping and polishing of the barrel just aren't practicable for the vast majority of barrel manufactures, or what most shooters can take advantage of for that matter. It's almost unheard of to hear a bad report of a Rock 5R cut rifled barrel, and several other high end barrel manufacturers share the same accolade. If a barrel manufacturer couldn't produce a repeatable product over time, these great reputations wouldn't exist. Their price tag reflects all that extra work, and cost, and Nth degree of performance.

My thoughts in summery,

Comparing two barrels from the same make, model, and made date should show very little to no measurable or quantifiable differences in accuracy.

Comparing two barrels from different makers is apples to oranges period. There are way to many variables b/t manufacturers even when they produce the exact same spec'd barrel to make any valid comparison.

[Pappabear]

Generally, those Colt SOCOM barrels are very accurate! I shot one for awhile in 2016 and shot one very extensively in 2010-2012.

Both were about .75moa shooters, the last group I shot with the first one was 1.2MOA with a NSN ACOG with MK262, prone on the mag. That barrel had over 15K rounds through it and had been cleaned once!

15K without a clean, thats solid living. We used to clean our guns every week, now we have a celebration if we clean them. I thank Todd Hodnett for this revelation.

PB

[Press Check]

Comparing two barrels from different makers is apples to oranges period. There are way to many variables b/t manufacturers even when they produce the exact same spec'd barrel to make any valid comparison.

Yep, apples and oranges between manufacturers, which is why the basis of my question gravitated towards the materials used and manufacturing process of what would essentially be considered duty-grade or rack barrels, and what separates one rack barrel from another. I think John, the Barrel Nerd at Charlie's, addressed that with the inconsistencies associated with the chrome-lining process, or at least that made sense to me.

Personally, and realistically, I only expect minute-of-man accuracy from duty-grade barrels. I don't shoot groups, and if I happen to find that a barrel is capable of shooting a minute, it's simply because it's in the process of sighting an optic. I don't chase minutes, chase load development, waste time trying to anchor my barrel to a specific round "it likes," or anything else. I train, shoot steel, use decent ammunition, and try to do my part behind the trigger, period.

[Clint]

Barrels from the same production run should perform similarly, but like any process, there are slight variations from part to part that are within acceptable tolerance and perhaps a few outside tolerance that should be caught and corrected in QC.

The variables are almost to numerous to mention, but broadly speaking, they are:
the blank
the machining fixturing
chamber tooling/gaging
crown
lining/coating

Large differences in one or many of these areas are probable between two different barrel makers. Just changing blanks can produce differences.