I’ve had a BCM barrel for years. There has been nothing wrong with it and it has proven to be very resistant to the elements. The only real complaint I’ve had about it is in the accuracy department. It has been fed a variety of ammo, but it never managed to group better than about 2.5-3 MOA. Now, that level of accuracy is acceptable for most carbine applications, considering military specifications allow the M4 to be up to 4 MOA. However, when paying the premium for a brand like BCM acceptable accuracy is frankly unacceptable.
My cursory search about BCM accuracy issues brought up a surprising number of results. Many have reported the same issues. Some simply chalked it up to, “You’re paying for reliability, not a match rifle.” I found it hard to believe that an Anderson barrel grouped better than one from BCM.
Years ago, I heard an old guy say that all barrels are different and some rifles prefer certain rounds. These preferences could even manifest themselves from the same batch of barrels on the same assembly line. At the time, I thought that was more of a fudd-ism and a convenient excuse to make up for a lack of fundamentals. Then here I was, shooting a rifle that would routinely group 3-4” at 100 yards and I knew I wasn’t that bad. I decided to exhaust all options and listen to his advice before giving up on this upper. I’m glad I did.
Twelve different rounds were tested. They varied between different brands, quality, bullet weights and construction. As you can imagine, this was a somewhat costly endeavor given the current state of affairs. This “testing” consisted of shooting 5 shot groups of each at 50 yards. The barrel was also allowed to cool as necessary, which wasn’t hard given its profile and the fact it was 27°F outside. The barrel never even became warm to the touch.
Why only 50 yards? I was limited by the magnification constraints of a 1-6x LPVO. It’s routinely used at 300 without issue, but the goal here was to test accuracy. Being able to see the grid lines simply provides a better aiming reference, which translates to more consistent results. Just double the group sizes and that will tell you the results for 100.
Why only 5 rounds? While a single 5 round group does not provide a statistical significance to demonstrate accuracy, it’s really a moot point. This test was to see which ammo my rifle liked. I have enough faith in my fundamentals and the ammo quality for this small sample size. Seeing a giant list of tabular data is nice and science-y, but it won’t necessarily confirm anything to you about your combination of ammo, rifle, and environment. Like ballistic calculators, they may be close or dead-on, but ultimately you have to confirm for yourself.
10 out of 12 of these groups reinforce my previous findings at around 2.5-3 MOA, which would explain my frustration about the accuracy issues with most ammo. From an outsider’s perspective, it may appear that these group sizes are from shooter error, as evident by the vertical stringing in 3 to 4 of the groups which normally suggests poor breathing technique. Rest assured; each group was done at a snail’s pace with every shot taken during the natural respiratory pause on the exhale.
There are two outlier groups, which should put concerns of poor fundamentals to rest. For some reason, this barrel likes the lighter rounds like ADI’s Match 55 GR Sierra Blitzking and Norma 55 GR FMJ. The ADI rounds grouped an impressive ½ inch, which translates to the coveted 1 MOA at 100 yards. I will take 1 MOA all day from a service rifle. Norma also seemed to group very well at ½ inch if you exclude the one flyer, which was possibly caused by a mixture of shooter error and the fact it was truly a cold bore shot. Does this mean the rifle will always group this well with this ammo? Maybe, maybe not. But the fact that it was able to do it twice with two different types of ammo is a great start.
Shown here is the author’s best group. ADI’s packaging is very unique. 
Pictured here is the author’s rifle used for the test.
It appears this BCM barrel was able to redeem itself. While it seems to be picky with its ammo, thankfully it delivers impressive results with a common round like Norma. More 55 GR rounds will definitely be chosen for future testing. This brings up some interesting observations, though.
Nothing about this test reinforces the typical folklore propagated by forum commandos. This barrel has a 1/7 twist rate. According to the internet, it should prefer heavier rounds. Based on this, the opposite seems to be true. This barrel is chrome lined, which allegedly doesn’t lend itself toward stellar accuracy. It’s also BCM, which isn’t known for accuracy either. While it isn’t sub-MOA, for a non-match rifle 1 MOA is more than respectable, especially when combined with great reliability.
Trust but verify. The internet sometimes contains decent guidelines, but they should always be confirmed. When talking about real standards of accuracy, there are simply too many variables to make generalities between rifles and ammo. PRS shooters and snipers know this better than anyone else, collecting lots of information in their DOPE books.
Many would argue this obsession with accuracy from a carbine is unfounded. AR-15’s aren’t meant to be precision rifles anyway, especially with the increasing popularity of shorter barrels on pistols and SBR’s. They can still attain a high degree of accuracy with the right combination, however. While they are limited in range due to ballistics concerns, rifles like the MK12/SPR/RECCE have proven to be very effective in urban environments where the engagements aren’t just CQB distances. Many times, intermediate distances present themselves in these settings and a little more magnification and accuracy goes a long way. Sometimes it even helps for closer distances like 150m and in, where a target may be partially obscured behind cover. 150m shots can be taken all day with a red dot or iron sights, but that’s on targets that are fully exposed to you. Knowing how dangerous CQB is and the fact most don’t possess the skill to provide accurate fire at range, I also like having the option of increasing the distance if I was ever placed in a terrible situation like that.
Red Dawn scenarios aside, what are the main takeaways from this? Recommendations are just that, not dogma. Go test different loads. Every rifle is different. It’s up to you to figure out what yours likes.
Scattered Shots 
Oh, man, I could write you a novel about barrels, but I’ll try to condense it down as much as I can here.
First, people should examine closely what the benchrest community has learned about barrels, because they’re not shooting for “good enough” (eg, 1 MOA at 100 yards), their matches are scored, in part, based on group size. For the benchrest community, they’re constantly chasing the group size issue, and right now, the record groups are under 0.100″ for five-round groups at 100 yards:
https://internationalbenchrest.com/records/group
OK, so condensing down what the benchrest folks know about barrels:
1. Single-point cut barrels are what give the best groups as you fire more rounds and the barrel heats up.
2. Thicker, shorter barrels often reduce group sizes, as such a barrel is stiffer. You lose velocity (approximately 25 to 30 fps muzzle velocity) for each inch you shorten a barrel – so, eg, if you go from a 20″ barrel to a 16″ barrel, you should expect to lose about 100 fps.
3. The bullet jump distance from the case to where it engages the rifling is a factor in group size, along with concentricity of the bullet in the case neck. Then we get into issue of choosing the specifics of the chambering in the barrel. This gets us into an issue which many people seeking to reduce group size no longer seem willing to do: handload.
LikeLike
where you been?!
LikeLike
Busy, and fighting with Google over the other email address I’ve used for this handle for awhile. Google wanted me to give them a phone number, and I didn’t want to, so I created a new email address for the commenting system here, as you see.
This spring has been pretty brutal in Wyoming. We had some serious snow, and there were a couple of weeks where I had a path literally two feet wide through a drift nearly five feet high to get into the shop. Fortunately, I had laid in enough coal to fuel the furnace to last those two weeks. Then we started having machines that move the snow break down, and I still have to finish repairing the IH tractor and Case backhoe, and there’s a carb on an ATV that needs to be rebuilt because it’s drooling gasoline when we fill the gas tank. This has just sorta been the winter when all the stuff breaks.
Now we just need to get on top of the weed growth – the weather is really hampering attempts to spray out weeds, as we’ve been having rain on most days in the last couple of weeks.
LikeLike