Archive for the 'Firearms' Category

Shooting Sports USA.

Armalite’s original blueprints specified a 20-inch barrel, 12-inch (measured from the upper-receiver face) gas-port location and a ballpark 12,500 PSI gas-port pressure level. Those are the “rifle” specifications, which work just fine. Therefore, the problem isn’t in the design. Rather, it’s in the redesign. The shorter the front end is, the more redesign has its influence. Carbine-length barrels and especially pistol-length barrels create a condition where using the same ammo there is higher gas pressure at the gas port.

An AR-15 has a “direct impingement” system. Propellant gas is bled off through a gas port in the barrel, this gas goes through the gas manifold or “gas block,” through a gas tube, and into the carrier key atop the bolt carrier, and that’s the end of the line—the resultant force deposited into the key starts the bolt-carrier assembly in motion.

Think of this gas system as a pressure chamber with two valves—one at the gas port and the other at the muzzle, and the moving bullet opens each valve as it crosses each plane. Therefore, the spacing of the valves matters greatly.

The better way to think of this is each is an orifice (even though an adjustable gas block is an adjustable orifice), not a valve.

As the bullet enters the barrel bore and moves forward, the space (volume) behind the bullet is increasing, which lowers the pressure of the contained gas behind it. More available barrel-bore volume before the gas port translates to lower pressure at the port. So, post-gas-port barrel length influences how long the system is “sealed” under full pressure, and the shorter the length, the shorter time. Again, the bullet is serving as a plug that’s sealing all the pressure in the system—until it exits.

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Approximate figures for M855 (genuine 5.56 NATO) chamber pressure is about 60,000 PSI; pistol-location gas port pressure, 50,000; carbine-location, 33,000; mid-length, 27,000; rifle-location, 19,000. Thus, 5.56 NATO is hot and getting hotter, and it has been for years.

Installing a heavier buffer and also a stouter buffer spring buys time. Both increase resistance to the bolt unlocking, thus delaying it from moving. The heavier buffer better resists movement and moves slower. The stouter spring increases in-battery load against the bolt carrier, increasing its resistance to initial movement, and the carrier also then moves slower coming back against the buffer.

“Just put an adjustable gas block on it” is also routine advice, and, yes, that helps, but ideally such devices should be used to tune function. If it’s needed just to make the gun run, then the chances are certain something else was missed, most likely in the architecture. That’s where we’ll find the cure.

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That’s easy enough with a carbine-length front, 16-inch barrel. A mid-length gas port is located 2 inches farther ahead of carbine-standard. It effectively also shortens the post-port distance by the same amount meaning lower pressure getting in and a shorter time the system is under maximum pressure. Both are good things.

If you’ve got a hankering for an AR-platform pistol, choosing a 10.5- or 11.5-inch barrel makes it possible to get a carbine-length gas system affixed, and that is a 3-inch additional length over the common 4-inch pistol-port, and a significant reduction in post-port length. That really tames a little gun.

I think it’s becoming fairly routine advice to choose the right gas system for your gun as a first step to correct over- or under-gassed systems, rather than tinkering with the gas block.

This is what the author is calling the “architectural” solution to the problem.  This isn’t exactly the same thing as having an adjustable gas block on a new AR-10 6.5 Creedmoor with a fixed 20″ barrel for folks who want to shoot hotter loads or those who want to hand load specialized cartridges and need to make slight adjustments on the block to ensure reliable operation.

I just can’t see .243 as an effective deer rifle because of its high velocity (penetration without deposition of energy), but I guess some guys swear by it.

Shooting Illustrated.

Let’s start with a simple definition: Mil-spec is “A document that describes the essential technical requirements for military-unique materiel or substantially modified commercial items. MIL-STD-961 covers the content and format for defense specifications.” In simple terms, mil-spec is a list of standards to which goods sold to the U.S. military must adhere. These standards might apply to truck tires, hats, t-shirts, and yes, firearms and ammunition. There is even a spec that specifies “Requirements for swim fins made of gum rubber for wear by military personnel for swimming purposes and for general utility.” Exciting stuff.

In the munitions context, a standardized “spec” ensures that everyone is armed with firearms that are of equal quality and with interchangeable parts. This simplifies logistics and ensures a basic level of quality. In the marketing world, mil-spec has taken on a life of its own. It is promoted as some sort of gold standard for quality when, in fact, it is a floor rather than a ceiling. The military itself is rarely at the cutting edge of innovation, instead relying on private industry to meet the needs of the force. Just because a product meets the mil-spec doesn’t mean that is the best thing on the block.

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If a firearm truly meets the military specification, we know that it satisfies a baseline standard for quality. If you’ve ever slept in a military sleeping bag, used a military backpack or hiked in military boots, you’ll probably agree that the issued items are rarely the best on the market. The same goes for firearms, which is something that we should all take into account when making our buying decisions. Just because a product is right for the military, doesn’t mean that it is the right choice for you.

Sounds like something I said before.  “Don’t slip past these paragraphs, because they explain why “Milspec” is 1:7.  It isn’t because 1:7 shoots M193 or M855 more accurately.  It’s because of the weight of tracer rounds.  As we’ve discussed before, the term Milspec doesn’t mean better, or worse, or anything at all except that it precisely meets the specifications outlined in the purchase order(s), excepting whatever variance notifications they might make on a given batch of guns.”

I expected the price to be astronomical, and while it ain’t cheap, it’s lower than I expected.  The MadPigCustoms web site can be found here.

Military.com.

LAS VEGAS — An Israeli company, working with Sig Sauer, recently showed a version of its high-tech, smart-shooter technology that the U.S. Army is currently evaluating in its Next Generation Squad Weapon Fire Control competition.

Smart Shooter Ltd. demonstrated its SMASH Fire Control System at a Sig-hosted range day for SHOT Show 2020. The SMASH is designed to help improve the accuracy of any shooter engaging stationary or moving targets in both day and night conditions, said Devin Schweiss of Smart Shooter Inc.

The SMASH “allows you to acquire, lock on and engage targets” using a weapon-mounted optic and special pistol grip that “allows the weapon to fire only when it’s a guaranteed hit,” he said.

“We are currently competing in the Next Generation Squad Weapon Fire Control competition … with a similar technology,” Schweiss told Military.com. “We are still adapting it, but it’s going to be a pretty good solution.”

Last summer, Army weapons officials invited defense firms to design and build prototypes of an advanced fire control system to go with service’s Next-Generation Squad Weapon (NGSW), a 6.8mm system that includes rifle and automatic rifle variants to replace the M4A1 and M249 squad automatic weapon in infantry and other close-combat units.

Smart Shooter has teamed with Sig, which was selected by the Army, along with teams from General Dynamics Ordnance and Tactical Systems Inc. and Textron Systems, for the final phase of the NGSW effort. If all goes well, the service plans to begin equipping infantry brigade combat teams with both NGSW variants and fire-control systems in the first quarter of 2023.

The SMASH features a lock button that’s mounted on the weapon’s handguard. The shooter looks through the SMASH optic, places the crosshairs on the target and presses the button to mark the target with a tiny rectangle.

As the information is fed back into the computer, the shooter keeps the crosshairs on the target and pulls the trigger, but the weapon will not fire unless the sights are lined up properly. If the target moves suddenly, the shooter continues to keep the crosshairs on the target. When the shot is lined up, the SMASH will fire the weapon, Schweiss said.

As opposed to, you know, like, um, maybe, perhaps, teaching shooters to shoot.

I’m sure this will work out swimmingly.

WiscoDave sends this video.  If a monkey can do it, then there’s no reason to stress test an AR-15 to see how many rounds we can put through it without cleaning before we destroy it.