Yep, the horse be dead, long live the horse.

Note that when we talk of "gas piston systems" for AR-type rifles, we are gathering a number of disparate principles under the tent. You can have long-stroke such as found in the Garand and AK, short stroke as in the SKS, cutoff and expansion as in the M14, and even a "gas trap-like" system. Each of these concepts has its own subset of pros and cons.

The gas driver is just one part of an integrated system. As with most in life, it's a matter of compromise.

The direct impingement shines in longer-barrel (16" and up) applications where accuracy, particularly at longer ranges, is the goal. The simplicity, light weight and low cost for the standard parts of the direct impingement system make it the choice for most non-full-auto applications.

Direct impingement pros:

• Free floated barrels are practical; the gas tube is the only, very minor exception to floating free.
• Simple construction, inexpensive, nothing to wear, foul or corrode.
• Light weight
• In the AR, ready availability of standard parts at extremely competitive prices

Direct impingement cons:

• Less insensitive to ammo variations.
• Much of the spent gas ends up inside the receiver(s).

The gas piston system shines in short-barrel, e.g., under 16", applications, which require NFA Registration (where state-legal) for us civilians. The high port pressures found in short barrels quickly erode the gas port. A well-designed piston system can accommodate the changes in port size over time. For much the same reason, gas piston designs can be more tolerant of suppressors (ditto with regard to NFA and state laws). The advantages may increase where full-auto (ditto again) is concerned.

Gas piston pros:

• Spent gas is vented externally.
• More tolerance of ammo variations

Gas piston cons:

• Can't free float, at least to not anything like the same extent as direct impingement.
• Heavier.
• More complex, more components to foul, corrode or go bad.
• Much more costly
• No standard, every system is different, heck, some vendors have changed designs two or three times! The owner is locked into a particular vendor for support, and that's assuming that the vendor will continue to support early iterations. If not, you have a thousand dollar tomato stake.

If you don't fire 1,000 rounds in a session, particularly if it's not full-auto, and you have a civilian-legal barrel length, you will be better off buying ammo and becoming more proficient than spending the money on a gas piston conversion. I'll submit that this will be the case for 99% of civilian shooters.

Now, let's go shooting!

Regards,

Walt