The SOCOM M4 Block II Barrel and Ammunition
BY Herschel Smith
1 year, 10 months ago
Before you dive into the video (and it’s a very good and informative video), I have some remarks. Ignore them if you want to dive straight into the video.
First, QC is a subset of QA, QA being a function of not only QC testing, but engineering, management oversight, problem reporting and resolution, and so on.
Second, the word accuracy is the most misused word when concerning firearms. Most of the time a rifle can be made accurate by adjusting the iron sights or optics. What most people refer to when they say a rifle is accurate or not accurate is precision. A small group on the target at the point of aim is both accurate and precise. A large group at the point of aim is accurate but not precise. A small group not at the point of aim is precise but not accurate, but can be made to be accurate by adjustments. A large group not at the point of aim is both inaccurate and imprecise. Accuracy can be adjusted into a rifle. Precision cannot. Precision is a function of the rifle and ammunition. Precision has to do with repeatability and statistically similar outcomes with increasing sample size.
And that last point is important. The Daniel Defense rifle did well compared to the Block II rifle, but they both suffered from imprecision. They are not 1 MOA rifles. Or are they?
With the right ammunition they both can be, as can be a lot of rifles that don’t shoot 1 MOA or better. Mass produced military ammunition isn’t high QC grade ammunition. To get good AR-15 ammunition requires buying those $1.50 – $2.00 rounds of .223 made by Hornady and other manufacturers who spend time and money on QC.
Both QA and QC costs money. It costs as much as the component does in most cases. If you want your rifle to be a 1 MOA or better gun, shoot high-QC ammunition. That means the powder has been metered, the bullets are not out-of-round, the center of gravity (CoG) is located at the centroid or thereabouts, etc. If you want to practice rapid fire, or fire under movement, purchase bulk military grade ammunition. If you want to shoot with precision (smaller groups), buy high quality ammunition. It will cost money.
Yes, barrel harmonics has something to do with all of this, as does machining tolerances, but the main point here is that good ammunition changes everything. He proves that right up front in the video.
On January 6, 2023 at 9:46 am, Bill Buppert said:
Herschel, as a fellow engineer, I really geeked out on your extraordinary explanation in paragraph three.
Well met.
Yes to QA and QC if harnessed to a well crafted verification and validation (V&V) regime on all the separate components then, how they act in concert with each other. Better yet, stress test to failure and work your way back. Tedious but necessary and it helps you climb or fall out of a failure tree [fault tree analysis]. Most failure causes are cascades of more than one proximate or/or root cause.
I also suspect that human factors have much to do with “expansion” of groups with shooting over time and less with accuracy. You will also note that the obsession with group size from non-benched firearms is a flawed measure any way you shake it.
Much of this is becoming a black box to newer engineers.
Baselines, baselines, baselines.
On January 6, 2023 at 11:54 am, George said:
Will the rifle shoot ‘one minute of bad guy’? Then it is good to go.
Military acceptance criteria for general use shoulder mounted weapons has historically been 2-4 MOA. (Sniping weapons not included.)
On January 6, 2023 at 3:20 pm, Chuck said:
QC is a subset of QA is so true. As I was taught very early in my career – you can’t inspect quality into a part.
On January 6, 2023 at 4:27 pm, Heywood said:
When I bought my LaRue I called them to ask about “break in” for the barrel (another hotly contested subject.) I spoke with the guy who actually made my rifle. He said, “Shoot it…that’s how you break it in. But use match ammo. I don’t want me or the gun blamed for your performance.” He said, shooter ability being constant, inconsistent ammo was by far the number one problem with being able to maintain good groups. I would tend to agree. But in my case, there are days where my shooting just plain sucks and there is nothing to blame except me.
On January 8, 2023 at 12:31 am, Georgiaboy61 said:
@ Herschel Smith
Just chiming in to second the praise of Bill B. above: An excellent analysis and write-up on your part, the kind of which we could use more of in the FA review world. I, too, have practically turned blue in the face trying to explain to non-scientists/non-engineers and non-mathematicians the difference between precision and accuracy. It is a pleasure to read someone who has such a firm grasp on the fundamentals involved.