#Energy

In the mid-1950s, the People’s Republic of China followed the Soviet Union’s example and adopted the intermediate 7.62x39mm round. This decision substantially helped to promote that cartridge’s ubiquity throughout the world, as millions of cheap Chinese-made SKS and AK rifles were exported to every corner of the globe. However, at the very end of Chairman Mao Zedong’s regime, an effort was started to develop a new, modernized caliber that would improve performance and conserve materials versus the 7.62×39. That program resulted in the 5.8x42mm caliber, standardized in the late 1980s with the DBP-87 and DBP-88 rounds. Unusually, the 5.8x42mm used a system with two different overall length standards, one of about 58mm for the DBP-87 rifle cartridge, and the other of about 62mm for the DBP-88 support round. This allowed the marksman’s rifle to shoot the DBP-87, if necessary, but also allowed for a longer, lower drag bullet to be put in the DBP-88 case, improving the ballistics of the QBU-88 marksman’s rifle and the QJY-88 general purpose machine gun.

In the late 1950s, after the first public demonstrations of the AR-15 and its new small caliber, high velocity cartridge, the Soviet Union took notice of the radical developments in military .22 caliber rounds in the United States. By 1959, four years before the adoption of the AR-15 as the M16 by the US Army, Soviet ballisticians were already testing Soviet-made replica 55gr spitzer FMJ bullets fired at over 3,000 ft/s from modified necked down 7.62x39mm cases. This program for a new small caliber high velocity lasted into the late 1960s, but it wasn’t until the mid-1970s that the 5.45x39mm caliber was eventually issued alongside the AK-74 rifle, a modified but significantly more effective variant of the previous 7.62x39mm AKM assault rifle.

At this point we’ve looked at the data for seven intermediate calibers currently on the market, each of which is – one way or another – influencing the discussion around the question of what next generation military rifle caliber will be. Those rounds were: The 5.56mm NATO, the 7.62x39mm Soviet, the 6.8x43mm SPC, the 6.5x38mm Grendel, the .300 AAC Blackout, the 7.62×40 WT, and the .25-45 Sharps. Initially, I intended for this series to be limited to just these seven, and I picked them as a cross section of different concepts and schools of thought regarding the intermediate caliber problem. Now, however, I have decided to expand this discussion to other calibers, including the latest developments outside the West. I figure I’ll just handle the extra clunk this introduces by breaking up the final comparative discussion into segments, that way all the data is presented clearly, and there are more posts for my readers to chew on. Everyone is happy.

Since we know that gunshot wounds follow physical laws – Newtonian mechanics, specifically – we can use physical quantities to describe what happens to a bullet when it enters a fleshy target. In a previous post, we were introduced to three physical quantities: Force, work, and kinetic energy. To see how these apply to a gunshot, let’s use the example of a hollow point bullet as it impacts and penetrates 10% ballistic gelatin.

In a recent post, I discussed four ballistics myths that I’ve heard over the years, and why they are just that – myths. One of these was the myth that the momentum of a projectile is equivalent or otherwise indicative of the stopping power of that projectile. I have for several years now been arguing that it is not, and the subject comes up again and again in my comments, so it’s high time I directly addressed it in a post. The short answer is “no”, as I wrote in “4 Ballistics Myths”: