The long loop of 9mm to 10mm to .40 S&W to 9mm by the FBI looks like a caliber argument until the medium of the test is revealed. When handgun bullets are compared to barriers and gel calibration charts, the focal question becomes not the one that asks about the size of the round. to whether a bullet is any good when it hits anything messy first heavy fabric, wallboard, sheet metal, or angled windshield glass then, nevertheless, get to where it counts.
The latter can be traced to one failure mode, that is the popular load of 9mm that could not consistently press deeply past the intermediate setbacks. Scott, who is a long time FBI ballistic researcher, put it in some stark terms to describe the cost: “It didn’t have the ability to penetrate intervening barriers and then to enter the human target and penetrate deep enough to disrupt a vital organ,” and then, “We buried two special agents because of it.”
It is starting there that the Bureau constructed an engineering language based on standardized testing. The protocol of the FBI is based on the calibrated 10 percent ballistic gelatin in order that various loads may be compared across lots as well as years but not merely across anecdotes. Calibration is not an act of worship, but rather an obligation; gel is put in a test to ensure a projectile with predictable behavior falls within a fine range of penetration. After that, rounds are requested back again after obstacles intended to invalidate the assumptions hollow points are based on: cloth that can seal up holes, auto glass that can bend and shred jackets, sheet metal that can bash noses, wall board that can destabilize. The predictable penetration corresponding to vital anatomy at imperfect angles was the result the FBI maximized. The 12-18 inches of gel penetration which is well known in the Bureau became the window since the short tracks might not reach the critical structures whereas the over penetration would put more risk in the downstream.
Within that scheme, 10mm Auto appeared to be an easy solution on a sheet of paper: more power, more room, less justifications. Practically it became a fleet problem. “We had enormous problems with 10 millimeters,” said Scott, and the problems were not as much as to do with toughness as to do with the scale of recoil and reliability in a mass of thousands of shooters and pistols. Smith and Wesson 1076 was introduced and according to Scott, there was one divided experience whereby about half the guns required custom-shop adjustments- and one faction ended up with pistols that they believed in and another group that could not maintain them on a regular basis.
The .40 S&W was an effort at the same concept identical bullets in a reduced case but it took the lessons of systems with it. Recoil impulse, slide velocity, size of pistol, and variability of shooters became more important than raw ballistic performance. Scott explained the natural response when the malfunctions showed up in smaller.40s: “Everyone initially thinks, Hey, what is wrong with the ammo?” The underlying problem was that full-power loads might exceed the lifespan and time limits of small-duty pistols as they were offered in a diverse variety of hand sizes and abilities.
The gel-and-barrier results started converging around the end of the 2000s and the early 2010s. Newer 9mm projectiles, designed with more secure bonding and controlled expansion, began to perform equivalently to.40 S&W over the FBI test without compelling the equivalent stability shortcomings. Dave Emery explained the process by which it was made possible as follows: “Because you allow us velocity,” a bow to the design room engineers receive when a cartridge can run fast enough to be expanded and at the same time remain reliable when subjected to service pistols. To Scott, his bottom line was: “there is not even a nickel worth of difference between the two.”
The decision was taken out of the laboratory and into human hands by data provided by shooting courses. Scott found that, between inexperienced personnel and elite operators, six out of ten shooters were found running faster and with more accuracy on 9mm than on.40 S&W. To an agency producing handguns on large scale, the caliber response turned out to be not a number but an imperative: capable of passing through barriers, predictable to penetrate, manageable recoil, and pistols that can continue to perform throughout the entire fleet.
