need 5.56MM, M855 load data
wolf
I am trying to duplicate the performance of the military SS109 / M855
cartridge. This is the .223 cal. steel core "green tip" 62 gr.
bullet noted for its accuracy. Does anyone know the factory or "mil
spec" velocity for this round? Using 26.5 grains of H335 I've driven
this bullet to 3200 fps, in a 1-10" twist barrel, but accuracy
sucks.
slam
wolf wrote:
#
# I am trying to duplicate the performance of the military SS109 / M855
# cartridge. This is the .223 cal. steel core "green tip" 62 gr.
# bullet noted for its accuracy. Does anyone know the factory or "mil
# spec" velocity for this round? Using 26.5 grains of H335 I've driven
# this bullet to 3200 fps, in a 1-10" twist barrel, but accuracy
# sucks.
My Book Semi-auto rifles data & comment (NRA Publication) lists 5.56
nato ss109 and xm855 with steel penetrator (Don't know if that's the
same as the green tip?) as 3050 F.P.S. @ zero yd's. You may want to get
this book it has alot of information on the .223 and AR15a1/AR15a2.
Also you indicated a 1-10 twist the ss109 and m855 were designed for a
1-7" twist. Hope this helps?
--
sl...@ghgcorp.com
Arne Carlsten
slam <sl...@ghgcorp.ghgcorp.com> wrote:
The "official" loading data for the M855 round (the officially accepted
as standard version of the XM855) is 26.1 grains of WC 844 under the
"green tip" 62 grain bullet. This is from the Army TM on small arms
ammunition. Velocity is specified as 3025 fps at 78 feet from the
muzzle. Chamber pressure as 55,000 psi.
WC 844 _may_ be available from some of the surplus powder dealers who
advertise in _The Shotgun News_, I've never looked for it before so I
can't say for sure one way or the other.
M855 will work fine in a 1 in 9" or 1 in 10" barrel; the 1 in 7" barrel
specified for the M16A2 and M249 SAW/AR/LMG is to allow the use of the
M856 tracer round. Backing off the velocity to around 3000 fps might
improve your accuracy. You're just getting large groups, right? And not
keyholes or other signs of understabilization?
--
Arne Gustav Carlsten
Flagstaff, Arizona
Chomh da/na le muc...
Doug Owen
wolf (tjs...@seanet.com) wrote:
: I am trying to duplicate the performance of the military SS109 / M855
: cartridge. This is the .223 cal. steel core "green tip" 62 gr.
: bullet noted for its accuracy. Does anyone know the factory or "mil
: spec" velocity for this round? Using 26.5 grains of H335 I've driven
: this bullet to 3200 fps, in a 1-10" twist barrel, but accuracy
: sucks.
Woha, boy, slow down. First off, this here M16A1/M16A2 Rifle
Marksmanship Field Manual I got here sez the A2 with the m855 round is
3,100 fps.
Second off, I've *never* heard this "noted for its' accuracy", where does
this come from? For sure it is trouble in a slow twist barrel, what are
you shooting? FWIW, this bullet has nearly *everything* working against
it WRT accuracy. It mass produced, thick jacketed, dual cored (ever
check out how uniform the penetrators are? They're not. Easy to get to
them, crush a few bullet tips in vice grips, or a real vice) with a steel
bit (no spring back, guaranteed poor bond) for openers. No serious
target bullet uses any of these.
Understand this book lists this gun/ammo at 50% probable hit on a man
size target at 300 meters, hardly a target gun. Typical *good* military
guns in a machine rest with good ball ammo are still *over* 2 MOA. Every
time. These are not target guns or ammo. If you want small groups, use
the HPBTM bullets, even the 55 grainers shoot very well in fast barrels.
With the "right" twist for the bullet they are tops, that's why "Match"
is in the name.
No serious High Power shooter uses this ammo, unless you make him through
the rules.
Doug Owen