XM193; Poor Google fu

[glock22357]

I spent some time checking the Algore-web trying to find concrete info on XM193, and if it really is a hotter load than M193. I found one reference that said that XM193 is really M193 that the military rejected.

I'm interested because this is what I keep in my 16", 1/9 twist M&P15T, and I'd like to know if this is the best FMJ round given my barrel length and twist. I also read that with the 55 gr. M/XM193 rounds, the twist rate really isn't that important, it's only when heavier bullets are used that the twist rate becomes important.

I did find some good info discussing fragmentation of M193, and that velocities need to be above 2700 fps for fragmentation to realiably occur.
From what I read, XM193 does about 3075 fps. from a 16" barrel, and keeps above 2700 fps out to about 150-200 yards.

So my questions are:

-Is X/M193 (55 gr.) the proper bullet weight ammo for my rifle (vrs. heavier 62 & 77 gr. rounds) given the twist rate and barrel length of my rifle?
-What is the real difference between XM193 and M193 ammo?
-Does barrel twist rate effect velocity to an appreciable degree?

I hunted for answers to these questions before I posted this, but my google-fu was weak today!:rofl:

[mvician]

http://ammo.ar15.com/ammo/

http://www.m4carbine.net/showthread.php?t=25709&highlight=xm193

http://www.thegunzone.com/556xm.html

http://www.m4carbine.net/showthread.php?t=9511

[KalashniKEV]

So my questions are:

-Is X/M193 (55 gr.) the proper bullet weight ammo for my rifle (vrs. heavier 62 & 77 gr. rounds) given the twist rate and barrel length of my rifle?

Optimal twist/weight is:

1/9 - 55gr - M193
1/7 - 62gr - M855

77gr (MK 262 MOD 0/1) will not stabilize, and will most likely keyhole from a 1/9.


-What is the real difference between XM193 and M193 ammo?


XM193 didn't meet contract specs and it's better to recoup some cost and sell it off than throw it away or remanufacture. I think someone's told you a tale...


-Does barrel twist rate effect velocity to an appreciable degree?


No.

[Constructor]

Winchester White Box is M193 for all practical purposes, works great in a 9 twist and available at Wally World cheap.

Some times I run across the Malayisian M193, it's pretty good surplus and hits the required velocity from a 20"
IMO the M193 55gr FMJ will have better terminal effects than M855 from a shorter barrel weapon.

[HogGlocker]

as stated, XM193 is MIL contract ammo that did not meet final MIL inspection [for whatever reason], hence the X designator.

I have a 1/7 twist and a 1/9. The M193 does shoot better in the 1/9 and my M855 [contract ammo] shoots better in the 1/7....marginally.

Inside of the ranges I shoot at [generally <200m] I am still able to take care of my target quite well regardless of the ammo I use in either twist rate.