July 02, 2020
By Tom Beckstrand
Ammunition is one of the most misunderstood categories in the firearms industry. Ammo often gets classified as “good”, or not, based on how it shoots out of a rifle or pistol, with very little thought or discussion about what it takes to create that ammo in the first place. Also, performance out of one firearm in a single, or even a handful of experiences, is far from a good indicator of performance on a broader scale.
To fully understand what separates one brand of ammunition from another, you have to take a look at the company that makes it. Who runs the show, the experience of the people involved, funding and engineering prowess are all critical aspects that will absolutely affect the ammunition’s large-scale performance. SIG Sauer’s ammo division has an impressive staff that has already demonstrated their ability to find solutions where others have failed.
300 AAC Blackout Case Study
Many are familiar with the rise of the 300 AAC Blackout. This cartridge has its roots in the Special Operations community where the need exists for a cartridge that feeds reliably out of AR-15-pattern magazines, uses the same bolt and magazine, and offers improved lethality over the 5.56x45mm. The shooting industry worked closely with the Special Operation community to produce it. With its larger projectile and ability to function reliably at both supersonic and subsonic velocities, the 300 BLK appeared to be just what the doctor ordered.
The one problem that had everybody stumped was how to get a bullet to expand at subsonic velocity. Good terminal performance at subsonic velocity allows soldiers to shoot suppressed with almost no signature. It has the added benefit of being hearing safe, even inside a small room, where anything supersonic would require hearing protection. Hearing protection complicates communication between teammates.
Subsonic bullets from the 300 BLK are long and very heavy, so they require a very fast twist in the barrel. The barrels also tend to be very short, to limit velocity to subsonic levels. So, additional twist is needed to compensate for that.
By the time enough testing data came in on barrel twist rates, the Special Operations guys decided a 1-7 inch twist was necessary to stabilize the subsonic heavies the way they liked. Accuracy became acceptable at subsonic velocity when the heavy bullets had the stabilization that the 1-7 inch twist provided.
However, that fast of a twist rate also caused the slow bullet to have poor terminal effects because it was so stable, that it wouldn’t yaw, tumble and break apart on impact. No one expected the slow, 220-grain .30-cal match bullets designed for magnum rifle velocities with correspondingly thick jackets, to fragment. There was some hope though that it wasn’t so stable that it couldn’t tumble and perhaps break apart. The hope was that if terminal performance expectations were kept low enough, the 220 grain-ish bullets might deliver. Nope. The heavy and super-stable bullets just drilled right into ballistic gel with no expansion or fragmentation, and very poor terminal effects.
There were a couple of small and innovative manufacturers that experimented with monolithic bullets that had heavily scored internal cavities. These bullets would open on impact at subsonic velocity and had good terminal effects. It looked like someone had found the answer to this complicated problem.
Those hopes soon turned to disappointment when testing showed that those bullets started to open upon leaving the muzzle when spun in a 1-7 inch twist barrel. This wouldn’t have been too big of a problem had it not been for the damage that happens when a suppressor is attached to the barrel. The bullet opens enough inside the suppressor to cause baffle strikes and erratic accuracy.
All appeared lost until the SIG Sauer ammo folks decided to look at the problem. The end result was the highly unusual 300 BLK V-Crown bullet seen here. It looks like no bullet I’ve ever seen because it solves a problem that, up until recently, no other manufacturer could address.
SIG Sauer leveraged the known advantages of a polymer tip to initiate expansion on this bullet. Polymer tips are the only way to start a bullet’s expansion on contact at low velocity. Supersonic bullets can use exposed lead, but that doesn’t work at 1,000 feet per second.
The next issue SIG Sauer handled was how to get 30 rounds to feed reliably out of a 30-round magazine designed for 5.56x45mm. The 300 BLK V-Crown bullet has a stepped ogive that has a shank of approximately .30-caliber. It steps down to a much smaller diameter as the ogive approaches the tip.
The purpose of the two-stage ogive is to allow the ribs in the magazine enough room to support the bullet orientation instead of interfere with it. Most 300 BLK bullets have the standard .30-cal ogives. These designs have a diameter that is too large to fit in a 5.56mm magazine without touching the ribs that run along the sides. The ribs push the bullet noses towards the centerline causing the rounds to sit crookedly once loaded. Instead of stacking parallel, the rounds lay diagonally across each other. This greatly increases column height of loaded rounds and makes it hard for the feed lips to hold rounds in place.
Once SIG figured out the polymer tip and stepped ogive, they still had to make the projectile. Where others were using monolithic bullets and high-speed lathes, SIG opted for the more machinery-intense option of forming dies and bullet assembly machines. This was a much more expensive option, but it allowed SIG to make what the Special Operations community needed, not what SIG felt like producing.
SIG’s solution to the complicated problem of producing an expanding subsonic bullet that feeds reliably out of 5.56x45mm magazines shows just how much depth they bring to the ammunition production game. They have the engineers to design and test, and the manufacturing capacity to produce what they design. It sounds like a simple task, but it was one beyond the reach of the rest of the industry in this case. You will be happy to know this bullet is available commercially for hunting/self-protection as the 300 BLK Tipped Hunting. For more information visit www.sigsauer.com.