5 years, 3 months ago
Ammoland has the details.
Coming in at 6.8 pounds, I really like the lightweight handguard. The price point seems right too (MSRP: $1100), and I think it’s a good addition to their stable given the usual unavailability (and high cost) of 458 SOCOM and the much higher availability (and lower cost) of 450 Bushmaster.
5 years, 3 months ago
I’ve never had any of these things happen to my guns, but then again, I’ve never had to put 500 rounds downrange in ten minutes. So there’s that.
5 years, 3 months ago
I think Chris does a really good job explaining this.
5 years, 4 months ago
American Rifleman has the scoop, but Ammoland does a little better job by giving stats.
Actually, neither had the scoop on me. I had discussed this very gun with Steve Mayer at RRA back in December of 2019.
My only complaint about Rock River Arms guns is that the ones that I’ve had seem to have weighty front ends. I had always thought they needed to be a little more on the cutting edge for reduced-weight hand guards.
With the unloaded weight of this gun coming in at 6.8 pounds, it seems like they’ve taken up the challenge.
Steve also points out that if you don’t want to buy the whole gun, they sell the upper separately.
5 years, 4 months ago
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.
[ … ]
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.
[ … ]
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.
5 years, 4 months ago
Tim Harmsen at MAC does more than 7000 rounds with the BCM.
5 years, 4 months ago
Via David Codrea, TTAG reports that this is apparently so.
But with the likes of Palmetto State Armory and others utterly offering complete AR-15s for under $400 right now there’s likely not much profit in AR platform rifles.
It shouldn’t been seen as a shock, though. Colt has bowed out of the civilian AR market due to lack of sales. There is an overabundance of product and a relative lack of demand since President Trump’s election in 2016.
It appears that the combination of the “Trump Slump” and Remington’s poor management have killed two well-known names in the AR-15 world.
It seems to me that if you’re going to make MSRs these days, they must fall into one of two categories. The first is high end rifles and pistols, e.g., Daniel Defense, LaRue Tactical, BCM, CMMG, and the second is the budget gun, e.g., PSA.
There is a huge difference in price point, and there just doesn’t seem to be a big market for the middle of the road price point.
5 years, 5 months ago
Good Lord. “Mowing down approaching armies” by sweeping the muzzle from side to side (If you ever try something like that at a range, you’ll be kicked off the range with prejudice, and this isn’t even discussing the fact that you won’t hit anything except by accident – if he was open-minded, which he’s not, it might be useful to take him to a range and actually demonstrate how this is done.). “Red hot magazines.” Red … hot … magazines. And there is just no data at all to justify his statement that mass shootings have to do with whether AR-15s are legal, nor is there any justification that machine guns couldn’t be used for mass shootings today with the relative ease of drilling two holes and dropping in an auto-sear. A determined criminal can do pretty much anything s/he wants. And note that he doesn’t allow that the criminal will have an AR-15, but you won’t for defense of home and hearth because you’re not a criminal. Then again, no one in Virginia will “grandfather” their ARs. No one.
Finally, mass shootings have gone way down, not of course including state-sponsored mass shootings in “gun free” nations, which is the reason for ownership of AR-15s in the first place.
Fisk it yourself. It’s not hard. He’s ignorant, prudish, and arrogant. And yet with Bloomberg money, an influx of controllers to Northern Virginia, and an absent voter base in the last election, he and his ilk is governing Virginia.
You just can’t make this kind of thing up. I love it when the progs self-identify as idiots. It saves us the trouble.
Prior:
UPDATE: Though per David Codrea, it may be impossible to shame him.
