Smith & Wesson 300 Whisper/300 Blackout AR-15 Complete Upper Assembly Using High Performance Ammunition

by Jeff Quinn

photography by Jeff Quinn & Boge Quinn

July 7th, 2012




Click pictures for a larger version.





Muzzle brake.



ACE skeleton buttstock on Jeff's DPMS lower.



Tactical Solutions Karma-7 sound suppressor.



Timney Trigger makes long-range accuracy easier to achieve.







Since being standardized as the 300 Blackout by SAAMI, the 300 Whisper cartridge has really taken off in popularity. The Whisper series of cartridges developed by J.D. Jones of SSK Industries has been around for many years, but only enjoyed a relatively small but loyal following. However, Mr. Jones’ work in developing the 300 Whisper and the others in the Whisper family is what started the search for a multi-purpose cartridge for both hunting and social work, that could be used with subsonic and supersonic loads in a variety of weapons. The ability of the 300 Whisper and Blackout to perform admirably in the standard AR-15/M-16/M-4 series of weapons has led to its popularity. The cartridge uses standard AR magazines, standard 5.56mm AR bolts, and standard AR gas system. Also, unlike the attempts to chamber the 7.62x39mm cartridge in the AR, the Whisper/Blackout works extremely well in the AR. While there are slight differences in the final specifications of the Blackout as compared to the Whisper, for the purposes of this review, they are interchangeable. That does not mean that every 300 Whisper rifle ever built will work well with the Blackout ammunition, nor the Blackout with every 300 Whisper cartridge, but it is generally understood that one can use both 300 Whisper and 300 Blackout in a 300 Blackout rifle, but only 300 Whisper ammo in a 300 Whisper rifle. Smith & Wesson marks their weapon to work with both, and that is what we are reviewing here. Also, I want the reader to be aware that there is a family of Whisper cartridges, from 300 up through 50 caliber (510 inch bullet diameter), but in this review, “Whisper’ will be referring to the 300.

I reviewed the 300 Blackout rifle from Advanced Armament Corporation a couple of months ago, but in this review, we will be looking at the 300 Whisper/300 Blackout upper for the AR-15 that is available from Smith & Wesson, along with some very specialized premium ammunition from Lehigh Defense that was not available to me in my previous review. The S&W upper assembly comes complete with a sixteen-inch M-4 profile barrel, quad rail, bolt carrier, bolt, and everything else need to quickly attach to any standard AR-15/M-16/M-4 lower receiver. I attached the upper to a DPMS lower that normally has my Alexander Arms 50 Beowulf upper attached.

Since my earlier review of the 300 Blackout, I have discovered Lehigh Defense ammunition. Lehigh makes both subsonic and supersonic ammunition for the 300 Blackout/Whisper, and the ammo is loaded with specialized bullets built for specific applications. The Lehigh ammo is loaded with Controlled Fracturing bullets that are designed to come apart after impact, with the pieces radiating into the target. Other Lehigh bullets are designed for maximum diameter expansion, with pedals folding out from the bullet shank for maximum tissue damage. Lehigh subsonic ammunition is built to expand at low impact velocities. These heavy bullets are machined to expand rapidly, producing pedals and/or fracturing like the supersonic loads, for maximum effect on target.

I fired the Lehigh ammunition on targets from twenty-five out to over 600 yards. As expected, the trajectory of the subsonic loads made hitting at distances greater than about 200 yards a challenge, as they are intended for close-range use from a suppressed weapon. However, even at greater distances, once I had figured out the trajectory, hitting the target was not too difficult, but was probably a waste of good ammunition in that effort. The supersonic Lehigh ammunition performed admirably out to the farthest shots attempted. Hitting steel rams at 547 yards was no challenge at all, shooting from a Target Shooting, Inc. Model 500 rifle rest. I ran the S&W upper with a Tactical Solutions suppressor attached at all times. All Lehigh subsonic Whisper ammunition is loaded to a nominal velocity of 1040 Feet-per-second (fps), in 300, 338, and 510 Whisper cartridges, but higher velocities were recorded from this sixteen inch barrel.

All accuracy and velocity testing was done at an elevation of 541 feet above sea level, with temperatures in the 105 degree Fahrenheit range, with a light breeze and a relative humidity of twenty-seven percent. All accuracy testing was done firing from a solid bench using a Target Shooting, Inc. Model 500 rifle rest. For accuracy testing, I used a Leupold Mark 4 4.5 to 14 power scope set to the highest magnification. The scope was attached using an Accushot one-piece base. Subsonic ammunition testing was done at fifty yards, and supersonic ammunition was tested for accuracy at one hundred yards. Velocities are listed in the charts below. Velocities are listed in feet-per-second (fps). Bullet weights are listed in grains.

Subsonic Ammunition

Ammunition Bullet Weight Velocity
Lehigh Defense Controlled Fracturing 170 1238
Lehigh Defense Controlled Fracturing 186 1146
Lehigh Defense Maximum Expansion 200 1172
Remington OTM 220 1064


Supersonic Ammunition

Ammunition Bullet Weight Velocity
Lehigh Defense Controlled Fracturing 140 2101
Atlanta Arms Pink Tip 125 2249
Remington OTM 125 2224

As can be seen in the charts above, most of the subsonic ammunition was not subsonic from this sixteen inch barrel. The 300 Whisper/Blackout cartridge was developed for use in short-barreled rifles (SBR) and submachine guns. Ideally, a barrel length in the nine inch range offers optimum performance with subsonic ammo, and it is for those shorter barrels that the ammunition is loaded. In the shorter barrels, the Lehigh ammunition runs at approximately 1040 feet-per-second (fps), and is much quieter at that speed. Having no SBR handy, my testing was limited to this sixteen-inch carbine. The supersonic really interests me, as I see this as a very good choice for a relatively quiet, low-recoil hunting cartridge. The supersonic 300 Whisper/Blackout is pretty much equal in power to the 7.62x39 and 30 WCF (30-30 Winchester) cartridges, and has plenty of power to harvest Southern whitetail deer.

Accuracy from the S&W upper was very good, especially with the supersonic ammunition. In fact, accuracy was excellent with all of the supersonic loads tested. The heavier subsonic loads showed signs of instability at 50 yards, but still, accuracy was acceptable at that distance. I am really anxious to try that Lehigh specialty ammo on whitetail deer this coming Fall. If it expands like the fired bullets which I have seen, it should be very effective.

In addition to my accuracy testing here in Tennessee, I carried the Whisper to the NRA Whittington Center near Raton, New Mexico last month for some long range shooting. The NRAWC is a great place for shooting at distance, as the arid ground makes spotting misses easy, for windage and elevation correction out to as far as one wants to shoot. For the 300, I limited my shots to a maximum of 600 yards with the supersonic ammo, and 300 yards with the subsonic. For the slow stuff, hits on random targets like small rocks and such were pretty easy to make out to around 200 yards, but after that, the trajectory is such that it would take a much better shooter than I to guarantee a hit. This is not a derogatory remark regarding the cartridge, the rifle, nor the ammunition. The combo performed very well. The subsonic ammo is designed for use from short to moderate range. Again, think short-barreled rifle or submachine gun. However, I was pleasantly surprised by the long range performance of the supersonic 300 ammunition. Hitting the steel rams on the metallic silhouette range was extremely easy from the Target Shooting, Inc. Model 500 rifle rest atop a solid bench. These rams sit out at 547 yards (500 meters for you tactical types), and the 4.5 to 14 power Leupold Mark 4 took all the guesswork out of holdover at that distance. Shooting standing offhand at targets of unknown distances out to 600 yards was again plenty easy, when I did my job well pulling the trigger.

The sound signature was greatly reduced, using both the subsonic and supersonic ammunition, by the Tactical Solutions Karma-7 suppressor. The S&W upper is already threaded 5/8x24 TPI, so installation was as easy as screwing the brake off of and the can onto the muzzle. As noted above, most of the subsonic loads were supersonic from the sixteen inch S&W barrel, but still noise was well-suppressed. While the Lehigh Defense subsonic ammunition is obviously built to be fired from a SBR or sub gun, it is still a good choice for longer barreled rifles and carbines. I know of no such plans from Lehigh, but with more sixteen inch carbines hitting the market, they maybe should consider a subsonic load for these longer barrels, in addition to the ones which they now manufacture.

The 220 grain Remington ammo was subsonic from the S&W barrel, and the sound signature greatly reduced. Of course, a handloader could tailor his loads to whatever powder charge was needed to achieve the desired velocity. The 300 Whisper/Blackout seems to be taking hold, but time will tell if it achieves the popularity that it deserves. The cartridge is a very versatile one, having applications in the hunting field, as well as its usefulness as a military cartridge for submachine guns.

Check out the extensive line of Smith & Wesson firearms and accessories online at

For the location of a Smith & Wesson dealer near you, click on the DEALER FINDER at

To order a Smith & Wesson firearm online, go to

For high performance subsonic and supersonic 300 Blackout ammunition, go to,, and

For quality optics, and a specialty premium riflescope set up for the 300 Whisper/Blackout cartridge, go to

For more information on the 300 Blackout and 300 Whisper cartridges, go to and

Jeff Quinn

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Leupold Mark 4 scope with illuminated reticle.



Factory ammo tested.



Subsonic ammunition (L to R): Lehigh Defense 170, 186, and 200 grain, Remington 220 match.



Supersonic ammo (L to R): Lehigh Defense 140 Controlled Fracturing, Atlanta Arms 125 Pink Tip, Remington 125 match.



Lehigh Controlled Fracturing (top) and Maximum Expansion bullets (bottom) have longitudinal machined slits to promote rapid expansion at low velocity.