While we are not using firearms at present, here is some information on RL body armor. Last I checked we were the only people allowed to wear vests. Not sure how this information converts to non-ballistic threats-like knives- but maybe some will find it interesting and/or useful.

NIJ Standard 0101.04 & .05

The National Institute of Justice (NIJ) has modified the 0101.03 ballistic standard for the testing of Body Armor. In general, the new 0101.04 standard is almost identical, but just slightly tougher. The interim 05 standard is simply an assurance that no Zylon is used in the manufacture of 04 Certified vests.

"Is armor that complies with NIJ Standard-0101.04 "better" than armor that complies with NIJ Standard-0101.03?

NO. It has only been tested to a different version of the standard."

...Guide to Police Body Armor, National Law Enforcement and Corrections Technology Center (NLECTC.org)

"NIJ Standard-0101.04 is not intended to restrict or otherwise influence the procurement and use of NIJ Standard-0101.03 compliant body armors...

... this revision for new model compliance testing does not invalidate or render unsuitable any body armor models previously determined to be compliant using NIJ Standard-0101.03 requirements."

- NLECTC.org

So, on either standard, you can rest assured you are getting a high-quality vest. There are MUCH more important factors to consider – such as how well the vest covers your body, and how comfortable it is.

The 9 mm FMJ test rounds are exactly the same, it is the secondary test round has been slightly changed - noted in bold below
NIJ 0101.04 & 05 Standard

Level

Tested for:

Difference from the 03 to the 04 / 05 Standard

II-A

9 mm FMJ (Full Metal Jacket) at ~1,090 fps
(332 mps)

.40 S&W Full Metal Jacket at 1,025 fps
(312 mps)

Threat round changed from
.357 Magnum at 1,250 fps to
.40 S&W at 1,025 fps

II

9 mm FMJ, at ~1,175 fps
(~358 mps)

.357 JSP at ~ 1,400 fps
(~427 mps).

.357 Magnum round increased in velocity from 1,395 to 1400 fps

Increase in velocity of 5 fps or 0.4%

III-A

9 mm FMJ at ~1,400 fps
(~427 mps)

.44 Magnum Semi-Jacketed Hollow Point at ~1,400 fps
(~427 mps).
.44 Magnum changed from Lead Semi-Wadcutter to Semi-Jacketed Hollow Point

It is important to note that Level II-A, II and III-A all stop the overwhelming majority of pistol projectiles you are ever likely to encounter (plus 12 gauge, OO buckshot), and also to know that NO armor is ever 100% ‘bulletproof’ under ALL conceivable circumstances.

However, these ratings often have a safety margin for penetration because blunt trauma is usually the limiting factor in certification. For example, Level II body armor would likely stop the III-A test standard, (9 mm submachine gun at 1400 fps) from actually PENETRATING through the Level II vest. But, the Level II vest would fail on blunt trauma impact (the NIJ deems any dent greater than ~1.7" (~44 mm.) on the soft clay test surface, a FAIL).

So, the advantage in increasing protection Levels from II-A, to II, to III-A, is NOT so much protection from PENETRATION of pistol fire, but a significant reduction in the blunt trauma received.

How Does Body Armor Work?

Kevlar®, one of the most popular ballistic fibers, is a synthetic material developed by DuPont, with about 5 times the tensile strength of steel by weight.

“When a handgun bullet strikes body armor, it is caught in a “web” of very strong fibers. These fibers absorb and disperse the impact energy that is transmitted to the vest from the bullet, causing the bullet to deform or “mushroom”.

Additional energy is absorbed by each successive layer of material in the vest, until such time as the bullet has been stopped.”