I can't find the actual SWAT article but here is the synopsis of "Filthy 14" (and sorry for the hijack but...) I'd actually like to see a piston gun do this.
FILTHY 14
As of this writing, EAG students have 31,165 rounds downrange through Filthy 14. During this evaluation period, it was cleaned once (as in one time), at 26,245 rounds. The end result is that Rack #14 was—and remains—filthy. It is filthy because it has been shot at class. Only at class. Every round that has gone down that barrel has been fired at class, with an average of approximately 1,300 rounds every three days. It has been lubed generously with Slip 2000 Enhanced Weapons Lube (EWL).
The combination of carbon and lube create (wait for it)…filth. It is so dirty that, while sitting in the rifle rack, it is almost a biohazard. The filth oozes out and contaminates other carbines adjacent to it.
But it is still shooting—and shooting well.
Rack #14 is a 16-inch Bravo Company Mid Length Carbine—mid length meaning that the gas system is two inches longer than the standard carbine gas system. This permits the use of a nine-inch rail with the standard front sight base. Use of a clamp on the front sight will permit a longer rail to be used.
The longer rail is necessary to accommodate some shooting styles, as well as to provide additional rail estate for the various white lights and IR lasers required to kill bad guys at night.
Subjectively, the mid length system has a softer recoil impulse.
The lower receiver is a Bravo Company USA M4A1, one of very few in circulation. It has a TangoDown BG-16 Pistol Grip. An LMT Sloping Cheekweld Stock (aka the Crane Stock) rides on the milspec receiver extension, as does a TangoDown PR-4 Sling Mount.
The upper is a BCM item, with a milspec 16.1”, 1:7 twist barrel. The barrel steel is chrome moly vanadium (CMV) and certified under milspec Mil-B-11595E.
The BCM bolt is machined from milspec Carpenter 158® gun quality steel, heat-treated per milspec, and then shot peened per Mil-S-13165. Once completed, each bolt is fired with a high-pressure test (HPT) cartridge and then magnetic particle inspected (MPI) in accordance with ASTM E1444.
The handguard is a LaRue 15-9, the nine-inch model to allow full use of the available rail estate.
We have a TangoDown BGV-MK46K Stubby Vertical Foregrip. We use TangoDown BP-4 Rail Panels.
The primary sight is an Aimpoint T1 in a LaRue 660 Mount. The T1 is still on the same set of batteries, and it has never been shut off. The back-up sight is the Magpul MBUS and the sling is the Viking Tactics VTAC.
This is a normal configuration for our guns, although stocks (Magpul CTR, Vltor I-Mod), BUIS (Troy), and day optic (Aimpoint M4s) may be substituted.
IN SERVICE
We received the carbine in late 2008 and put #14 into service shortly thereafter.
At Brady, Texas, in March 2009, it suffered a malfunction, which was reduced with Immediate Action. The bolt was wiped down at 6,450 rounds.
At Prairie du Chien, Wisconsin, in May 2009, it had several failures to extract, and the extractor spring was replaced at 13,010 rounds. This is far beyond the normal extractor spring life under these conditions.
At Wamego, Kansas, in June 2009, two bolt lugs broke at 16,400 rounds. We replaced the BCG. Considering the firing schedule, this is within normal parameters.
At Columbus, Ohio, in November 2009, we had several failures to extract at 24,450 rounds. The shooter gave it a field cleaning and replaced the extractor and extractor spring.
At 28,905 rounds, we finally cleaned Filthy 14. As part of our year-end maintenance schedule, we inspect and replace parts as necessary. Filthy 14 looked like the inside of the crankcase of Uncle Ed’s ’49 Packard. It was disgusting to look at and contaminated everything near it, somewhat like the toner cartridges for old printers.
I plopped it into a parts washer filled with Slip 725 parts cleaner, and 20 minutes later it was clean. Mostly clean, anyway.
We have never used a bore brush in the barrel of this gun. We did run a patch down the barrel twice, but that was all. At 50 yards it still shoots two-inch groups, and we understand that it might not at 100 yards and beyond, but we are happy with the fact that, even at 50 yards, the gun is capable of tighter groups than most of the people running it.
We have never used a chamber brush in this gun either. We were often told that this was an absolute must.
Sure…
At the last class in Casa Grande, Arizona, at approximately 30,000 rounds, we had several failures to extract. We replaced the extractor spring and wiped down the BCG.
By the time you read this, we’ll likely have another 3,000 to 4,000 rounds through Filthy 14. At that point we’ll probably retire it. We’ll reuse the LaRue rail, the sights and, after rebuilding the lower, replace that old and well-worn mid length upper with something else.
Fourteen will continue, but just not as Filthy 14.