Harkamus, I have editted my post because after doing more research RBCD is not what they claim to be. The link given shows the clear story. See my post above this for it.
I have also found another good link here -
http://www.m4carbine.net/showthread.php?t=19888
This one deals more with their pistol ammunition.
So what you have with the RBCD pistol ammo is basically the use of a nylon "cup" to support the small lead tip of the bullet which then has the copper jacket swaged around it in a bullet forming dye. The lighter weight of the bullet enables a faster powder to be added to the cartridge case to achieve very high velocities which would give very high pressures. The appropriate thing is to ensure that these pressures do not exceed the maximum SAAMI pressure level for the cartridge case.
Given the poor reputation for making false claims by Le Mas which must have been known by RBCD who made the ammunition for them I would be careful on this issue. Certainly I would want a new heavy recoil spring on any pistol which was used to test them.
However, to get back to my point about the 5.7 FN and comparing it with what else is out there ... one of the reasons I have stuck with my 9mm SIG for over 20 years and carried it all over the world is the availability of "proper" ammunition in 9mm to use in specialist care roles.
Here is a link which shows the testing of certain ammunition into Geletain after penetrating level II soft body armour -
http://www.brassfetcher.com/index_files/Page315.htm
As you can see the 5.7 is tested and using it's original military round ( which is not available for general public purchase ) it penetrates about 6 inches. Ideally though for proper effectiveness penetration of 11 to 12 inches is required.
Then check out the 9x19 ( standard 9mm ) Slovakian 71g THV AP round which was fired from a Glock 19. It penetrated 13.6 inches. Twice the depth of the 5.7. The bullet retained it's normal diameter though and did not expand. This will be a consequence of it's construction. Likely it is a steel core with a teflon coat and a moly coat added on top designed not to expand so that it can conform with various military treaties on ammunition and can be used legitimately by military forces. This is the standard armour piercing formula. The vest was only level II ... most modern soft vests are level IIIA ... the Slovakian round would likely have penetrated around 11 inches with this type of armour. It is I believe the level of armour the round is developed for.
This type of ammunition is easily available "worldwide" in 9mm if working in the military or security business and is one reason why using a 9mm pistol has been a logical choice. It is far more effective than the 5.7 FN round.
One interesting point from these tests is that a "civilian" legal round for the 7.62 x 25 Tokarev ( the 85g FMJ from Sellier and Belliot ) actually out performed the 5.7mm restricted round. It penetrated 11.8 inches and expanded to .46 in calibre. This would give excellent stopping power/wound chanel capability. It is also available in quite cheap pistols. The Tokarev T33 and the CZ 52.
I am a big fan of the Tokarev ... the detachable trigger mechanism design was so advanced that it was incorporated into the Sig P210 ... and if you get a good one of these they are remarkably accurate and flat shooting.