Federal M vs XM (5.56) and XM193 vs XM855

X vs XM…XM193 vs XM855?!?

Learn the confusing differences between Federal’s X and XM designations of their 5.56 ammo, as well as the differences between XM193 and XM855 rounds.

Plus ammo recommendations!

Federal 5.56 M193 vs XM193


In a nutshell, “M” by itself means that it meets military specification (mil-spec) while “XM” means it does not.

But just keep in mind that mil-spec is very stringent and even a small thing out of specification can lead to tons of ammo being rejected.

And overwhelming consensus/review is that XM193 is some fine shooting ammo.  But for some sleep-inducing reading pleasure, you can check up the mil-spec standards of M193 for yourself.

Federal must have gotten so many questions that they put up a site that describes XM193.  Emphasis is done by me.

XM193 product is first run, first quality product manufactured at the Lake City Army Ammunition Plant for Federal Cartridges and is made to Federal specifications typical for commercial ammunition.

All XM193 product is the same regardless of the sku or part number. (ie. XM193C is the same as XM193F, XM193CBP and etc … )  The only difference is the package configuation.

Sadly the page is now down (as of 2016) but here is the link (slow load) where I grabbed a cache of it from 2012 and a screenshot of the cache below.

Federal XM193 FAQ
Federal XM193 FAQ

I think they were just trying to calm fears that it was inferior ammo for the shooting public.

If you’re trying to be technical…I guess it is inferior to mil-spec, but still fine enough for commercial specification.

And to make it more confusing, the M vs XM only applies to Federal/American Eagle.  Other manufacturers such as PMC use the M193 designation.

As far as I know, it’s really good ammo but just because it’s called M193 doesn’t mean it’s mil-spec.

So Can You Buy M193?

Once it is designated M193, it should be going to the military so you’re going to have a hard time getting the “real deal” without possibly breaking some laws.

We do not recommend that.

But we do recommend the below ammo:

M193 vs M855

The M193 cartridge is a 55 gr lead core surrounded by a copper jacket (FMJ-BT, full metal jacket with boat tail).

While the M855 “green tip” cartridge is 62 gr and has a steel core “penetrator” at the tip which helps it go through barriers more easily (also FMJ-BT).  You can see the lighter gray of the steel below.

M855 Cutaway, Bearingarms.com
M855 Cutaway, Bearingarms.com

To make things a little more confusing, you might also see SS109, which is more often the designation of the bullet projectile but for some non-US ammo manufacturers, it could refer to the entire cartridge.

Green Tip SS109 Projectiles
Green Tip SS109 Projectiles

Should I get M193 or M855?

You’re probably thinking…”penetrator” sounds pretty badass and it goes through barriers more easily…so I need it.

In reality, M193 does a better job against soft targets under 100 yards since it fragments more than the M855 which has the steel core.  After that length, the M855 seems to catch up.

M193 Fragmentation, Ammo Oracle
M193 Fragmentation, Ammo Oracle

Also, keep in mind that the barrel twist of your rifle will also dictate how well the heavier projectile will fair.

If you have a 1:7 or 1:8 twist, it will be fine, but if you have the more commercially popular 1:9, you’re better off sticking with the M193 55 gr.

Ideal Bullet Weight vs Twist, Shooters Log
Ideal Bullet Weight vs Twist, Shooters Log

Now for penetration, below is a picture of regular PMC Bronze .223 (approximation to XM193) vs XM855.

PMC Bronze .223 vs XM855 Green Tip
PMC Bronze .223 vs XM855 Green Tip

The depth of penetration against the 3/4″ steel plate was .20 inches for the 55gr and .35 inches for the XM855.

The complete video is here, but get ready for a lot of misses (I’d start halfway in).  So I’d say it does penetrate more but it doesn’t cut through steel like butter.

And because it penetrates, it will do a good number on steel targets and potentially spark a fire, so many ranges do not allow it.

Last thing, is the price difference.  Most likely you’re going to see 193 slightly cheaper than 855 by a few cents.  Nothing too much of a deal breaker.

So to sum it all up:

  • Pricing is pretty similar
  • Some ranges do not allow steel core bullets such as the M855
  • M193 likes 1:9 barrels while M855 likes 1:8 or 1:7
  • M855 penetrates slightly better
  • M193 better performance against soft targets under 100 yards

And FYI, there was a brief scare in 2015 that the ATF was classifying M855 as armor piercing and taking it away from civilians, but they’ve since backed down.

Supplies dwindled as people thought it was going to be banned, but now it’s almost back to normal.

And our recommendation with the 855 thrown in there.  See our Best Ammo For Your AR-15 for more.

Got any questions? What do you shoot through your rifle? Let us know in the comments!

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7 Comments on "Federal M vs XM (5.56) and XM193 vs XM855"

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My boxes of XM193 literally say “military grade” on them, for even more confusion!

We been shooting here on the property for 27 years. All or m4s AR’s came with 1-7 twist. Daughter shoots 55gr with a red dot site. She likes up the red dot with the standard ar front site, no carry handle in rear. The girl can almost always hit the eggs at 150 yards and it’s pissing me off. Wife has a scope on her build on top of ar carry handle.. She has some trouble but seems to better with 62 gr. She is the sniper, also I struggle to keep her scope or carry handle from comming loose.… Read more »
Norm Morris
Good overview, thanks, but have to disagree on the twist rate comment. When I bought my first AR in 1994, 1:9 was it; there was no such thing as a faster twist, and those guns had no problem at all with M855/Ss109 “penetrator” ammo. To this day my 1:9 Bushmaster Dissipator shoots better with the 62 grain bullet than with the M193. When the M4 and 1:7 standard came along everyone assumed that was the best for all bullet weights, even 40 grainers, but the 1;9 is better for those light loads, and equally accurate and stabilizing as long as… Read more »
Joe Smith

I’ve contacted Federal. The difference in the M vs XM designation isn’t that the XM failed anything. XM designated ammo was not submitted for military batch acceptance. Same ammo, no defects. Just to clarify.