I am ocassionally reminded that not everyone shares my appreciation for the .30-06 as the true "do it all" cartridge. Some years ago, our old friend from Virginia, Dave Whitford, became one of those lost souls who succumbed to the siren song of the AR15 and its promise of high scores with low recoil - more's the pity, for Dave was a true .30 caliber man. However, there is hope; in this article Dave tells us of his recent work with a new .30 caliber cartridge for the AR15 and its applicability to Highpower competition. It would appear from Dave's effort and experience that the 300 BLK is not just for the Carlos Hathcock pretenders, but might, in fact, find a useful purpose among competitive shooters. Well done, Dave! -GAS-
300 BLK for Over the Course
by Dave Whitford
AAC stands for Advanced Armament Corporation in Georgia, the cartridge’s developer. AAC is under the same conglomerate umbrella as Remington, Bushmaster, DPMS, and several others, which explains why Remington pushed for SAAMI approval. AAC makes rifles and carbines, Remington produces ammo, Forster makes die sets, and Pacific Precision makes the reamers. As an addicted wildcatter, I loved this availability of no-trouble SAAMI-spec reamers and dies when I adopted my 300 BLK project in February 2011.
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| (L) 300 BLK with 125 gr. Speer, (C) .223 Remington, (R) 300 BLK with 155 gr. Hornady |
The cartridge, like the .30 US Carbine round, is a pistol cartridge in a short-rifle. It’s a non-proprietary update of JDK's proprietary 300 Whisper from the late 1980s, early 1990s. Apparently Remington and AAC tweaked chamber specs or cartridge dimensions slightly so as not to infringe on JDK's proprietary claim.
However, despite the small changes, the new AAC cartridge is the ballistic equivalent of the .300 Whisper and its wildcat .300-221 Fireball spinoffs. Like the 7.62x39 Russian, it boasts .30-30 ballistic equivalency, although more efficiently with less gunpowder. More power than the .30 US Carbine comes from cut-down .223 brass that is 0.020″ bigger in diameter and about 0.040″ longer.
In the middle to late 1990s, good new .22 caliber bullets and faster-twist barrels made AR15s competitive over the course out to 600 yards. Because the ARs don’t kick much, they reduce fatigue and give a rapid-fire advantage. The .30 caliber scoring rule applied for the sub-caliber bullets: if a bullet hole was in question whether it would break the next-higher scoring line, the scorer inserted the NRA .30 caliber plug to determine the outcome.
The AR successes apparently annoyed the die-hard .30 caliber NRA fathers. Viewing the AR shooters as cheaters who used less-than-manly rifles, they passed a punitive rule that said, “If your bullet hole doesn’t break the line, you get the lower score. Period!”
This rule change annoyed me since day one. I shoot several local short-range reduced-course competitions at 100 and 200 yards so that I can shoot as many weekends year ‘round as possible. Like any shooter, I lose points when my bullet holes miss the center. I especially loathe the points lost to skinny-bullet squeakers that close in on but fail to break a scoring ring. Being annoyed about this for numerous years, I’ve been shopping for a cheap, low-recoiling .30 caliber AR to shoot. The 7.62x39 Russian was out due to its funny magazines, bad feeding reputation, and new-bolt requirement.
Three-plus years ago I became too old, slow, and deliberate, to score well in sitting rapid-fire with my beloved bolt guns and switched entirely to AR-15s. My first was a 6BR crafted by Eric Bellows. Eric also produces these in 6BRX, 6.5BR, 7BR, and 30BR and became my AR mentor.
When I reviewed the new 300 Blackout info in January, 2011, I thought I’d struck gold. After working through some development glitches, I still think so. Here was a ready-to-go AR15 cartridge that required no new bolt or magazines, but would make .30 caliber bullet holes in 100-yard targets.
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| Larry Racine at the lathe. |
I contracted with Eric’s uncle, Larry Racine in New Hampshire (LPRGunSmith.com) to chamber and fit the barrel and I had Pacific Tool & Gauge send him the new reamer. Larry has a hoard of hammer-forged .30 caliber barrel blanks that were originally destined to be replacements on M1A rifles. Their manufacture was overseen by Creighton Audette in the 1980s, and their bores are like mirrors. When Larry was finished with his work, the barrel blank had become a heavy, twenty-inch, chrome-moly, 1 in12″ twist AR15 barrel.
AAC’s Robert Silvers was generous with his advice for my project. He’s apparently the company’s chief promoter and developer of 300 BLK ARs; most of which are suppressed, short-barreled M4 carbines for law enforcement and “black-ops” organizations. AAC also provides a 300 BLK bolt gun on a Remington Model 7 action.
Robert advised that if I were to use a 20-inch barrel, I’d need to use a carbine-length gas system. The gas port, he said, would need to be in the 0.080″ to 0.110″ range. I alerted Larry and he drilled a minimum-size gas port. Sneaking up on the final gas port one numeric drill-bit size at a time with function tests according to Eric’s prior tutelage, I arrived at 0.104″ as the appropriate gas port size for my rifle.
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| AR15 float tube with offhand riser and handstop before finishing. |
My 6BR has a 28″ barrel. When I later got a 26″ barreled .223 upper from John Holliger’s White Oak Precision, I put a short bloop tube on it to extend the sight radius to be the same as on the 6BR; ditto for the 300 BLK, which resulted in its long, heavy bloop tube.
The carbine-length gas system meant that I’d either need to cut and alter an expensive free-float tube from White Oak or make my own. I made my own, which was cheaper if you don’t count my expensive workshop time on an interesting and fiddly project. As normal, this project began with a trip to Lowe’s to get electrical conduit, the basis for many of my rifle innovations.
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| AR15 float tube, finished and installed on the rifle |
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| Top view of float tube, showing cut-out for gas block clearance. |
Although Remington now makes both supersonic ammo with 125 gr. bullets and subsonic ammo with 220 grain Sierra Match Kings for the 300 BLK, component brass for handloading is scarce. Remington brass was briefly available from CMMG in Missouri, but they are presently out of stock with none expected until mid-September 2011. I shorten .223 brass just below the body-shoulder junction, de-burr it, form the new neck and shoulder through the full-length die, trim it to length, and re-anneal it. It’s not hard, just tedious.
I start with cases that weigh either 91 gr. or 92 gr., regardless of manufacture. These cases are at the low end of the weight spectrum, which goes beyond 98 gr. Weight changes in a case so small represent significant percentage differences in capacity. Although you can get cut-down and prepared brass from suppliers like CMMG, I mistrust it because I don’t know whether they began by weight sorting. I feel safer with weighed brass because of the quick-burning pistol powder and near-max recommended loadings.
Robert tested his 300 BLK on Reading’s 600-yard range one miserable Massachusetts day this spring. When he told me, I scoffed. He used a prototype 130 gr., high-BC, Sierra flat-base, which must’ve eased his plight.
Then I ran the ballistics through the Sierra Infinity program and produced some startling numbers, showing that Robert was in the correct ballpark. Although I hadn’t considered using my 300 BLK for anything farther away than 200 yards, Infinity told me that it’s also a viable 600 yard rifle, despite a rainbow trajectory. For example, the 155 gr. A-Max that works well for me, starting at 2250 feet-per-second, retains more than 1400 fps at 600 yards. Wind drift in a 10 mile-an-hour crosswind is 38″, only five inches more than a .223 80 gr. Match King starting at 2750 fps. While not ideal, the 300 BLK is a workable full-course rifle. Imagine my surprise!
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| .300 BLK with the Sierra 100 gr. Varminter |
My two best loads have used the 125 gr. Speer TNT over 18 grains of H110 and the 155 grain Hornady A-Max over 17 gr. of H110. At 2.260″ overall length, the 155s fit the magazines better for rapid-fire. The 125s are too short for such loading, but they still feed OK.
I’d hoped to use 110 gr. Sierra Varminter to minimize recoil, but they pattern from my rifle rather than group. Recoil from even the 155s, however, is moderate because of the tiny powder charge. Shooting the rifle reveals that it’s no .223, of course, but it’s a pussycat compared with my .30 caliber rifles of yore.
I test the 300 BLK differently from any of my previous rifles, for which I used the traditional shoot-the-group-and-measure-it technique. Instead, I fire ten rounds from the magazine, and then see whether I can cover the group with a paper circle cut the same size as the MR-31 target’s 10-ring. It’s the quick way to determine whether the rifle can shoot “possibles” on the 600-reduced-for-100 target. For my present purpose, possibles are good enough. I’m not chasing half-moa groups.
I’m delighted at shooting possibles now because things didn’t begin that way. It was a gamble whether the 300 BLK would be a decent target cartridge, given its “spray-and-pray” heritage in AAC’s suppressed, full-auto M4s. In fact, early results were dismal. Both Eric and Lonnie Miller told me, “Take the upper apart and put it back together. Sometimes that’s all it takes.” Lonnie, a former armorer with the Army Rangers, also offered several juicy assembly tips.I did as suggested, cracking the upper-receiver forging in the process because I had used blue Loctite on the barrel-nut threads during the first assembly. While awaiting a DPMS upper-receiver forging from Midway, I fixed the cracked upper forging the best I could and reassembled the upper as I do my bolt guns: anti-seize lube on the barrel-nut threads and only a modest amount of torque… far less than normally recommended for assembling ARs. The rifle shot better, not great yet, just better!
The new DPMS receiver is better in several respects. Although sold as a “stripped upper”, it’s ready to go as-is because it has no provision for port-cover hardware or the forward–assist assembly, neither of which I need or want. It also has no brass-deflector bump on the side. The deflector on the previous forging was dinging the necks of my hand-built brass upon ejection. One piece was so badly deformed that I needed to throw it away after only one firing. Finally, the DPMS upper is a little heavier-duty throughout.
These were pleasant surprises because I wasn’t aware of the differences when I ordered. Best of all, the rifle began shooting possibles right away with the new forging. My $80 mistake with the first forging really paid off in the long run.
I’ve entered the rifle in six 100-yard competitions since early May with mixed but generally improving results. The big problem was a wandering zero. I isolated that to a moving bloop tube in the most recent competition. After offhand and sitting rapid-fire, I noticed that the bloop tube had migrated almost an inch forward of the witness line I’d marked on the barrel when I first installed it, obviously from recoil. I further tightened the clamp nut and fired the 30 prone shots. The tube moved another eighth inch and might well have caused the vertical stringing on the prone slow-fire target, on which I scored only 191-4X with a pair of 8s.
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| Bloop Tube joint with J-B Weld |
I re-installed the bloop tube at the witness line and re-zeroed it at the range. Then I slathered on green Loctite, the kind that “wicks into” a preassembled thread or joint. While the Loctite cured, I consulted Lonnie, who recommended that I also add some J-B Weld epoxy, which I did.
Now it’s test time again. I’m satisfied that the overall upper assembly – minus the bloop tube – is up to Highpower competition requirements. I’ve never before had a mobile bloop-tube on any of my boltguns or on the .223 upper, but I’ve also never before made one so long and heavy. I can always just mount my foresight on the barrel.Far as I know, I’m the first to put the 300 BLK into Highpower competition, where it fills a good niche.
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| Dave Whitford's 300 BLK AR15 NRA Match Rifle |
