Home Forums Reloading Varmint Rifles 5.56 loads in 223 chamber

I believe the issue of 5.56 ammo in bolt-action .223s is all about jamming the bullet into the lands. There's an awful lot of conflicting "information" out there, and some of it comes from folks I would think I should be able to trust...nonetheless, I think they are wrong. Here are some links to info put out by folks who should know...

This came from wiki, IIRC. Not the most reliable source of politically controversial information, but usually is fairly reliable on technical questions:

5.56�45mm NATO

5.56�45mm NATO with measurement, left to right: bullet, empty case, complete round with bullet in case
Type Rifle
Place of origin United States
Service history
In service Since 1962
Used by NATO
Wars Since Vietnam War
Production history
Designer Remington Arms
Specifications
Parent case .223 Remington
Case type Rimless, bottleneck
Bullet diameter 5.70 mm (0.224 in)
Neck diameter 6.43 mm (0.253 in)
Shoulder diameter 9.00 mm (0.354 in)
Base diameter 9.58 mm (0.377 in)
Rim diameter 9.60 mm (0.378 in)
Rim thickness 1.14 mm (0.045 in)
Case length 44.70 mm (1.760 in)
Overall length 57.40 mm (2.260 in)
Case capacity 1.85 cm3 (28.5 gr H2O)
Rifling twist 178 mm or 229 mm (1 in 7 in or 9 in, originally 1 in 14 in)
Primer type Small rifle
Maximum pressure (EPVAT) 430.00 MPa (62,366 psi)
Maximum pressure (SCATP 5.56) 380.00 MPa (55,114 psi)

According to the info I've been able to dig up, SCATP standards are practically identical to SAAMI standards. EPVAT specifies a pressure measurement in a different physical location---near the neck, I believe.


Here is a page out of a 1994 publication of the Department of the Army. Chamber pressure for M193 ammo is given as 52,000 psi.



For now, I am in the camp that says 5.56 NATO ammo is NOT loaded any hotter than commercial .223 Remington can be. I've posted the evidence to support that position, but I won't claim it PROVES it. There may be more to the story.