.50 Cals and UL Level 10 Bullet Resistant Glass

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If you’ve spent some time at a shooting range in the last several years you’ve certainly noted the increasing number of handguns chambered for .50 caliber bullets.  Previously only seen in the battlefield, these half-inch-diameter bullets (nearly the size of a 12-gauge shotgun slug) were first adapted to sidearms in the 1980s, and popularized by the semi-automatic Desert Eagle target pistol.  2003 was a banner year for .50 caliber handguns, when Smith & Wesson–famed for their Model 29 .44 Magnum, which Dirty Harry endorsed as “the most powerful handgun in the world”–developed a .50 caliber Magnum round.  The revolvers chambered for these finger-sized cartridges are almost cartoonishly massive, even when compared to Dirty Harry’s hefty long-barrel Model 29.  A .50 cal pistol weighs in around five pounds, and is almost a foot-and-a-half long from hammer to muzzle.  Despite this girth, the pistol’s cylinder can only accommodate five of these outsize cartridges.  The UL specification for commercial bullet resistant glass doesn’t list anything more powerful than a .44 Mag or a deer rifle, leaving one to wonder:  What kind of bullet resistant glass do you need to stop these giant bullets?

.50 CALIBER PISTOLS VS. .50 CALIBER RIFLES

Total Security Solutions vice president Jim Richards is quick to point out that these newer .50 caliber pistol rounds are an entirely different beast from the military rifle rounds of the same name.  The most common military .50 caliber bullet is the US Browning machine gun round.  Developed in the early 1900s, these are still regularly deployed in the battlefield as a standard full-metal jacket, tracer, or armor piercing bullet, as well as exotic incendiary and saboted sub-caliber projectiles (the latter offering superior accuracy over extremely long distances).  Standard issue .50 cal cartridges generally have a 700 grain bullet (that is, one three times heavier than a .44 Mag) that travels at 3,000 fps (three times faster than a jet fighter), with a muzzle energy exceeding 13,000 foot-pounds (more than thirteen times that of a .44 Mag).

But no one is going to sneak up on you with a military .50 cal: The bullet itself is over five inches long (i.e., longer than the barrel on the popular Glock 19 pistol), and is fired by a four-foot-long, 90-pound, tripod-mounted rifle.

While the .50 caliber standard and Magnum rounds are large–the largest for a standard production pistol–they aren’t nearly the size of the .50 cal military cartridge, and pack nowhere near the punch.  These .50 caliber pistol bullets weigh 325 grains, travel at 1,400 feet-per-second, and leave the barrel with 1,500 foot-pounds of force.  That’s nothing to scoff at, but also isn’t going to punch through a bunker door.

BULLET RESISTANT GLASS FOR .50 CALIBER RIFLES

BULLET RESISTANT GLASS FOR .50 CALIBER RIFLES

Dig deep into the UL standards and you’ll find that there is an established benchmark for stopping the .50 caliber military round: Level 10.  Jim has never heard of a commercial Level 10 system: there is no demand for it in the consumer market, because .50 caliber rifles are so very scarce.  Such a rifle costs $12,000 and fires rounds that cost $2 to $5 a piece.  The vast bulk of consumer .50 cal rifles are in the collections of extremely wealthy gun enthusiasts; according to the US General Accounting Office’s best estimate as of 2001, only a few thousand .50 cal rifles are floating around the United States.

While these rifles are rare in civilian life, every branch of the US armed services–and most military forces worldwide–use .50 cals.  What would it take to stop that bullet?  According to Jim, you’re looking at an “awful thick, awful big, and awful heavy” hunk of bullet resistant glass.  If he were tasked with designing such a system, he’d begin with three inches or more of glass-clad polycarbonate, which would weigh more than 30 pounds per square foot.

BULLET RESISTANT GLASS FOR .50 CAL PISTOLS

As for those ever-more-common .50 caliber hand-canons, Jim has good news: Although not rated for this use, it’s likely that conventional Level 4 bullet resistant glass would stop a standard or Magnum .50 cal bullet.  A .50 caliber pistol throws a 325 grain bullet at 1,500 foot-pounds to a speed of 1,400 feet per second.  By way of comparison, a .44 Mag bullet is 240 grains (a bit lighter), with 1,000 foot-pounds of energy (a bit less force), getting up just past 1,400 feet per second–and that can be stopped by a Level 3 system. Move up to Level 4, and you can stop a .30-06 hunting rifle bullet (the little cousin to the .50 caliber military round); this is a 180 grain bullet (clearly much lighter than the .50 cal pistol round) with 3,000 foot-pounds of energy (twice as much as the .50 cal pistol) moving at almost 2,800 feet per second (again, nearly twice as fast as the .50 caliber Magnum bullet).

Is the Level 4 UL tested and certified to stop a shot from Dirty Harry’s new best friend?  Not yet.  Would Jim feel safe standing behind Level 4 bullet resistant glass?  Yes he would.