3 Oct 13
On many modern, gas-piston, gas-adjustable, military rifles, the ratio of gas that is vented to the outside, to that which goes directly into driving the piston, is adjustable. With powerful ammunition, a significant percentage of gas can thus be vented, as there is still more than enough left to run the piston, and the milder setting reduces recoil and wear-and-tear on the rifle itself. Conversely, when shooting less-powerful ammunition, the ratio can be adjusted upward so as to insure reliable functioning.
The ever-popular FAL, SIG/556, and XCR series fall into this category. Even the venerable M14 (M1A), which has no gas adjustability as it comes from the factory, can now be fitted with an after-market device that provides adjustable gas settings.
As I’ve indicated in the past, some routinely run the such rifles “wide-open.” That is: venting none of the gas and thus directing all of it into the piston. This practice ostensibly assures reliable operation, particularly when your ammunition supply is a “grab-bag” mixture of rounds thrown-together from several sources at the last minute.
However, there is a problem with routinely running your rifle “wide-open,” and we experienced it last weekend in NV.
The violent bolt movement associated with “wide-open” operation is not only hard on the gun itself and is, as noted above, associated with unpleasant recoil, particularly in 7.62×51 caliber (308), you’re also risking the extractor pulling through the case’s extractor ring, leaving the fired case in the chamber, and rendering your rifle thus instantly inoperative, until the case can be tapped out from the muzzle via a full-length cleaning rod!
So, there are risks associated with too much gas, just as there are risks associated with too little. The “Goldylocks Zone” will invariable be in the middle somewhere.
You don’t get to “relax!”
“Doubt is unpleasant, but certainty is absurd.”