Inspect the new upper for what? What can be seen short of an armorer teardown? The gas tube alignment is about the only thing that can be inspected OTC.
Not just gas tube alignment, but properly staked gas keys, buffer weight and spring coils, gas rings, the finish on internals, etc. That's even before you go to the range to look at your casing ejection pattern, test different cartridges for properly cycling, check for bolt bounce, and so forth. And then afterwards, performing a thorough cleaning, checking for gas leakage under the gas block (evidenced by excess carbon under the block) and unusual wear, and checking casings for distortions and excessive rim damage. While some leakage is considered "normal", out of spec barrel contours and gas block dimensions can leak enough gas to cause or contribute to issues.
While we can tune a rifle or carbine to sort of run in almost any configuration, the bottom line is "Should we?"
If you start with one parameter way out on the ragged edge of reliability, every other parameter gets strained to accommodate the original outlier.
Didn't we already do so a number of times with the system and moreover, make it standard? In order to overcome higher pressures and longer dwell times associated with shorter gas systems, adding heavier buffers and springs became common. In fact, I would wager that many manufacturers (including the "reputable" ones) use H and H2 buffers with their rifles, not the standard carbine buffer. Why? To handle the over-gassing issues common with carbine-length gas systems. Even many rifles with mid-length gas systems use H buffers.
There are already products for shorter dwell times and lower gas pressure. Blast-redirecting/back-pressure increasing muzzle devices are common with SBRs with their short barrels and dwell times. Lighter buffers and springs, adjustable gas blocks, as well as lighter weight bolt carriers, are very common in the 3-gun circuit. A rifle with a 16 inch barrel and rifle-length gas system should function reliably with standard carbine parts, but if someone wants that added margin, there are parts available. However, it's unnecessary for normal function and associated more with tuning for a particular load to squeeze every bit of performance without losing reliability.
For absolute reliability, it is better to be sitting somewhere near the middle of the scatter plot. That minimizes ammo sensitivity, temp sensitivity, moon phases and all the other minutia you mentioned.
That's why I think that the mid-length system is probably better for patrol rifles. Patrol rifles are often of mediocre quality, despite supposedly using mil-spec parts according to their respective manufacturers. As such, having a mid-length gas system helps with over-gassing and under-gassing issues that are common with the platform.
Some of which is straight bullshit such as the "mistimed gas rings". A lot of the rest is specific to hobby grade equipment.
Stacked tolerances.
"Softer recoil" and "Smoother recoil" are both pretty subjective terms. Reduced wear on components is another term that is rarely quantified. Is the reduced wear 2% or 18%? What does that mean on an upper that the vast majority of us won't shoot to failure or end of service life? Faster reacquisition of sights is something that can sort of be measured with split times, but is likely more of a training/practice function.
A mediocre rifle is probably fine for most shooters, just like a mediocre sedan would suit the needs of most drivers. However, that doesn't lesson the demand for configurations that suit particularly purposes, even if the user doesn't have the actual
need or
ability which would make the configuration necessary. How many shooters actually need a Geissele or AR Gold trigger? How about nitrided parts? Match or Wylde chambers? How many shooters shoot enough to shoot out their barrels? So do most users outside of the competition circuits
need the performance of a rifle-length gas system? Probably not. Just like most drivers don't need vehicles with 300+ horsepower or 300+ lb. ft of torque.
Well chosen muzzle devices can make a fair amount of difference while having no reliability downside.
TANSTAAFL Generally speaking, yes. However, every muzzle device has advantages and disadvantages. Recoil-compensating muzzle devices have more side and user-end blast, as well as muzzle flash. Flash suppressing muzzle devices have more blast. Blast-redirecting/back-pressure-increasing devices have more recoil and muzzle flash. An acceptable drawback in a flat range in broad daylight, may not be acceptable in an enclosed room, or at night. Every situation has the right muzzle device, but there isn't a right muzzle device for every situation. Multi-role muzzle devices are compromises and don't do everything well.
I am just not seeing the juice be worth the squeeze when we already have mid gas systems that work so well on 14.5" and 16" systems that are GTG off the shelf with no tuning required.
We also also have off-the-shelf rifle-length gas systems that are GTG. Most, if not all, DMR/SPR and 3-Gun builds are rifle-length gas systems.
Is it worthwhile to squeeze the performance of a rifle-length gas system out of a carbine-length rifle? That's up to the end-user to decide. Personally, I don't recommend it for everyone, but I prefer shooting it more than most of my more commonly-configured rifles. YMMV
