ARs, PDWs and pistols in 300 Blackout are a hoot to shoot suppressed, but for the ultimate in quiet try a 300 Blackout in a bolt-action rifle.
At the height of the Vietnam War, the U.S. military started toying around with a sub-sonic .30 caliber cartridge that could be fired from a M-16-type rifle. The need for such a weapon was obvious to special forces units who needed a quiet round for killing Viet Kong combatants on missions where a lot of noise just wouldn’t work. Popular movies from that era often show Green Beret warriors taking out a North Vietnamese Army sentry with a suppressed weapon as they snuck into a prison camp to rescue some captured American soldier.
From Dream to Reality
That’s the “Hollywood” version of suppressed weapons from that time, but more likely, the military found that downed pilots needed a quiet weapon to defend them as they escaped and evaded enemy troops in their attempt to escape a lengthy visit to the Hanoi Hilton. What the engineers and designers down at the United States Air Force Armament Lab at Eglin Air Force Base came up with was a 7.62x28mm cartridge, which propelled a 172-grain match projectile to the 1,050 fps range. When the Vietnam War faded away, so did the obscure little cartridge.
Almost, but Not Quite
Fast forward to the early 1990s, and a similar cartridge was developed by SSK Industries’ owner J.D. Jones. We’ve been providing the .300 Whisper to the military for a number of years,” Jones said. “It’s been in use by the military, and a lot of other three-letter agencies.” I discussed Jones’ family of “Whisper” cartridges at length while we drove from a Las Vegas hotel to a shooting industry media event prior to the SHOT Show more than 20 years ago.
J.D schooled me about the excellent penetration qualities of heavy sub-sonic bullets, and the versatility of the same cartridge when driving much lighter bullets at twice the speed of sound. Jones has built quite a reputation with his custom gun business over the years, specializing in AR-platform and bolt-action rifles shooting the .300 Whisper.
If You Love Something, Let It Go
One thing is for certain, Jones kept tight control over the trademarked Whisper cartridge name. This led to a non-standard wildcat, the .221/.300 Fireball. You see, Jones learned early on that the .221 Remington Fireball case worked the best to form brass for his .300 Whisper. He even tried to get Remington to make some brass with his SSK head stamp, but that fell on deaf ears. Nonetheless, the cartridge earned a following, with several shooters opting to save a few dollars and chamber rifles in .221/.300 Fireball.
Some of those .221/.300 Fireball fans included several friends in West Tennessee who were serious DIYers. A large number of Stevens Model 200 bolt-action rifles were rebarreled from .223 Remington to the .300 Fireball. One of the guys shooting this cartridge in the late 1990s, Gary Cook, liked what he saw. He liked it so well that he outfitted several of the West Tennessee game wardens working for him with similar setups. The “rabbit cops” liked the little rifle in an animal damage control role, owing to its quietness. No loud rifle shots means no calls to the Poacher Hotline from concerned neighbors.
Loading Lesson Learned
One of the things that I learned about the .300 Whisper’s chamber several years ago was that just trimming a 5.56 NATO case wasn’t a sure path to success. The chambers on the original SSK .300 Whisper rifles had chambers with throats that were sensitive to case neck thickness. Some military ammunition comes constructed with thicker case walls. Merely trimming those down and necking up to .30 caliber produced cases with overly tight necks when loaded. Firing this ammunition could pose pressure problems with the tight-chambered Whispers. One of the AAC remedies to deal with chamber pressure problems was to increase the length of the throat.
Gun Details
A compact carbine 300 Blackout bolt gun, the AAC Micro 7 300 AAC Blackout measures 34 ½ inches overall. Its barrel is a light contour 16-inch tube with a 1:8-inch twist. To accommodate a suppressor, the muzzle is threaded 5/8-24 threads per inch. It comes fitted with a low-profile muzzle thread protector.
The stock is black molded plastic, but is a big improvement over the earliest Remington Model 7 synthetic stocks. Several years ago, I spent a season hunting with a pre-production stainless synthetic Model 7. If the stock brushed against brush, a jacket zipper, etc., the stock “rang,” which at the least was annoying and at the worst game scaring.
This Model 7’s stock is much more solid in construction and significantly deadens sound. Textured in strategic locations, this stock wears a raised, rough finish on the wrist of the stock and the bottom and sides of the forearm. The stock measures 28 7/8 inches, its length of pull spans 13 inches, and it wears sling swivel attachment points fore and aft. Although not necessary, the butt wears a soft 1-inch recoil pad. A significant component of the stock is an adjustable cheek piece. It allows 1 ¼ inches of rise at the front of the cheek piece and 2 ¼ inches at the rear. This allows the shooter’s eye to align more easily with large objective scopes, and helps with high scope mounting.
The Micro 7 300 BLK offers flexibility with optics mounting. Instead of a standard Weaver-style or other scope ring base, AAC opted to include a mounted Picatinny rail that bridges the action. Just below the ejection port, the stock has a cut-out that makes loading easier. Although loading is easy, ejection is iffy with a fired case. It appears the Picatinny rail mount interferes with ejection and causes the empty case to frequently fall back on the magazine stack. This Micro 7 comes in black nitride finish, which includes the bore and chamber.
Magazine capacity is four rounds. This rifle wears one of the best triggers I have ever used on a production-grade Remington bolt-action rifle. Its X-Mark Adjustable Trigger came from the factory set at 5 ¼ pounds. It has no creep, no over-travel and breaks like a glass rod. It was a simple task to pull the barreled action from the stock and use an Allen wrench to back the trigger pull weight out to its minimum 2 1/2-pound setting. Once adjusted, I put a small drop of Locktite on the screw to keep it in place.
Down Range
This rifle is a hoot to shoot! Whenever I take my youngest son, Luke, to the range I have to watch him closely to be sure he doesn’t shoot up my test ammo before I have a chance to do my test firing. The majority of shooting we do with the Micro 7 is with an AAC Cyclone suppressor screwed in place. Loaded with subsonic rounds and a silencer in place, the recoil is no more than a .22 LR, and its bolt action is even quieter than an AR-platform in the same caliber.
Bettter Optics
To provide a good opportunity to shoot small groups at 100 yards, I mounted a Leupold Mark V 3.6-18X scope. This is a 35mm tube scope, so I opted to affix it in a set of JP Enterprises mounts. A Mil hash reticle, this is a first focal plane optic.
Handloading tinkerers will enjoy working with this rifle. Even though several manufacturers provide factory loads that will fit this rifle, a wide range of .30 caliber bullets beg to be tried. To ascertain the velocities of various loads, an Oehler 35P recorded data at 15 feet from the muzzle. Providing a basis of comparison, I elected to use a Bulls Bag set atop a solid bench, and used sand bags at the rear.
Now that the 300 BLK has gained popularity, it has provided a lift to sales of .300 Whisper ammunition and rifles. Hornady joined Corbon by adding two factory loads for .300 Whisper. Rifles chambered in 300 BLK will fire .300 Whisper with no discernible difference in chamber pressure or performance.
Factory Fodder
Remington loads two bullet weights for 300 BLK. One is subsonic for the silencer crowd and the other is a “high velocity” round relative to it case size. Neither bullet would be classed as a hunting projectile in construction, leaning more precisely toward target shooting or tactical use. Since AAC touted the 300 BLK as a replacement for the H&K MP5SD when it is chambered in a 9-inch-barreled AR, it makes perfect sense.
Fired from a 16-inch barrel bolt-action, the Remington 125-grain Open Tip Match (OTM), the smallest 100-yard 5-shot group recorded was 1.218 inches. After firing more than 100 rounds of this ammo from this rifle at targets, 5-shot groups at 100 yards averaged 1.48 inches. Velocities from a 10-shot string typically averages 2,076 fps, and I’ve fired several. On the other hand, one 10-shot string posted an extreme spread of 436 fps, and the standard deviation (SD) was a rather high 159 fps. Some chronographed strings posted better SDs in the mid 60 fps range.
FACTORY LOAD PERFORMANCE
| Velocity | Accuracy | |
| Remington 125 gr. OTM | 2,076 | 1.218 |
| Remington 220 gr. OTM | 887 | 1.737 |
| Hornady 110 gr. VMax | 2,303 | 1.056 |
| Hornady 208 gr. AMax | 938 | 1.017 |
Remington’s 220-grain subsonic loads are built to be quiet, and they certainly are when chugging along at an 887 fps average. Their standard deviation was calculated at 35 fps, and their extreme spread was 133 fps. The smallest 5-shot group measured 1.737 inches. The extreme spread for this load showed up down range, too. Typically, it would cluster four rounds in a group about ¾ inch in size, and then would throw a single round about 2 inches low and right of the cluster.
Hornady leans more toward hunting-style bullets for their .300 Whisper loads. Their high-velocity load is a 110-grain VMax bullet, which averaged 2,303 fps. Its 374 fps extreme spread and a standard deviation of 134 fps was disappointing. Five-shot groups at 100 yards averaged 1.42 inches, while it did cluster its single best group into 1.056 inches.
Hornady’s first sub-sonic loads were tipped with 208-grain Amax bullets. This load averaged 938 fps. The smallest 5-shot, 100-yard group measured 1.017 inches center to center. The average for all groups was 1.28 inches. Today’s best subsoinc hunting loads from Hornady use their 190-grain Sub-X bullets.
Some Handloading Recipes
Not just satisfied with handloading to raise the performance of this rifle, I’ve run a number of cast bullets down the pipe in my quest for cheap, relatively accurate fodder. One bullet that has my interest is the 247-grain Whisper, which is molded from a 5-cavity mold from Night Owl Enterprises. I ordered a mold that drops three plain-base versions and two bullets dimensioned to accept gas checks.
Since most of the rifles chambered in 300 BLK or Whisper have a fast 1:8 twist, I decided to start casting relatively hard bullets from 50 percent wheel weights and an equal portion of linotype. This alloy produces a bullet with a Brinell Hardness Number of 22, which seems to be adequate. So far, I’m not finding any sign of leading in the rifles shooting it. The plain-base version of this bullet averages 1,149 fps when driven by 10.0 grains of IMR 5744. Its standard deviation is 11 fps, and the extreme spread is 34 fps.
HANDLOAD PERFORMANCE
| Handload | Velocity | Accuracy |
| NOE Mold/Cast 247- gr. Whisper | 1,149 | 1.322 |
| Sierra Match King 210 gr. | 1,030 | 0.749 |
| Barnes TTSX 110 gr. | 2,200+ | 1.121 |
The gas-checked version of the 2470grain Whisper averages 1,144 fps, its standard deviation is 7 fps, and the extreme spread was 18 fps. This load isn’t subsonic, which was my goal. It’s not objectionably loud with a suppressor, though. Accuracy is acceptable, too. I have not fired a 5-shot group that measures over 2 ½ inches yet at 100 yards, and the smallest measured 1.322; not bad for a bullet cast from free tire shop scrap.
The 210-grain Sierra Match King driven by 9.3 grains of H110 shoots well. I’ve laid in a good supply of 300 BLK Remington brass, and primed it with Federal Benchrest primers. This load stays subsonic, averaging 1,030 fps. The average 5-shot group is 1.12 inches, and the smallest measured 0.749 center to center.
Another bullet I like for this rifle is Barnes’ 110-grain TTSX. So far, loading with H110 it hovers above 2,200 fps and shoots just over MOA. I’ll keep pushing this bullet with this powder and others to settle on a good whitetail round at ranges under 200 yards.
SPECIFICATIONS
| Manufacturer: | Advanced Armament Corp |
| Model: | Micro 7 |
| Caliber: | 300 AAC Blackout |
| Action: | Bolt |
| Barrel Length: | 16 ins. |
| Capacity: | 4+1 Rounds |
| Muzzle: | 5/8-24 Thread |
| Finish/Color: | Black |
| Grips/Stock: | Synthetic Adjustable |
| Sights: | AAC Picatinny Rail |
| Type of Barrel: | Threaded |
| Used Gun Price: | $780 |
AAC’s Micro 7 in .300 BLK is a great little rifle that’s fun on the range and a handy little woods carbine. After Remington went bankrupt in 2020 and sister company AAC got sold off, no new Model 7s in 300 BLK are being built. But, they’re common in the used gun market and not too hard to find. Give one a try any you’ll become a fan, too.
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