What is the difference between XM193 and M193?

M193 refers to a military specification:
[url]http://www.biggerhammer.net/manuals/tm43-0001-27.pdf[/url] (see page 10-3)
The spec calls for a 5.56mmx45mm NATO round loaded with a 55 grain (listed as 56 grains in that document.... close enough I guess) bullet that will travel at 3,250 feet per second muzzle velocity.  This velocity is faster than most regular commercially available ammo with the same bullet (commercial ammo is loaded to be within .223 Remington SAMMI specifications).  Also, military ammo is usually sealed with tar around the bullet and primer for extreme resistance to water.

XM193 is the name of a product that Federal is selling.  I have shot several thousand rounds of this stuff.  The headstamp on the cartridges ("LC") seems to indicate that it is made at Lake City in Independence, Missouri (one of the US military's ammo manufacturing facilities, now managed by [url=http://www.atk.com/]Alliant Techsystems[/url]).  It is made to M193 specifications in as much as the bullet is 55 grains and the velocity is about as hot as you will find (I have measured it at 3,250 to 3,300 fps).  There has been some inconsistency in the lots that were produced in that some have been sealed with tar and some have not.

I don't know how Federal is getting Lake City ammo to sell, but it might have something to do with the fact that ATK owns Federal and CCI/Speer in addition to managing and running the Lake City plant for the government.

If you are looking for newly manufactured ammo made to the M193 specification, then you can't go wrong with the XM193.  (Some people actually care about the tar sealant, though because they want to store their ammo until World War 3 breaks out.)

Another newly manufactured ammo made to the M193 specification is Winchester Q3131A made in Israel (under contract with IMI, who makes ammo for Israel’s military).  I have found the Winchester to be about 50 fps or so slower than the Federal XM193.

Ammo Man sells both Winchester Q3131A and Federal XM193: [url]http://www.ammoman.com/[/url]

You can also buy IMI branded and headstamped M193 spec ammo that is probably very similar, if not the same, as the Winchester Q3131A.
[url]http://www.botach.com/IMI/IMIAmmo/556mm%2055gr%20M193%20FMJ.htm[/url]

Awesome. Thanks Q!

XM193 is made at the Lake City ammunition plant on the same equipment as the military issue M193 ammo. It is the cartridge case from the M855 round with the 55 gr bullet on it. The US military still uses the 55 gr round because there are still M-16A1's in the inventory.