The .25 NAA is a pistol cartridge introduced by the North American Arms company in 2002. It was originally created for use in a smaller and lighter model of their Guardian pistol.

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.25 NAA
.25 NAA basic shape
Type	Pistol
Place of origin	United States
Production history
Designer	J.B. Wood
Designed	1999
Manufacturer	North American Arms
Produced	2002–present
Specifications
Parent case	None
Case type	Rimless, bottlenecked
Bullet diameter	.251 in (6.4 mm)
Neck diameter	.276 in (7.0 mm)
Shoulder diameter	.333 in (8.5 mm)
Base diameter	.337 in (8.6 mm)
Rim diameter	.337 in (8.6 mm)
Rim thickness	.046 in (1.2 mm)
Case length	.745 in (18.9 mm)
Overall length	.960 in (24.4 mm)
Case capacity	9.75 gr H2O (0.632 cm3)
Rifling twist	1 in 16 in (410 mm)
Primer type	Small Pistol
Maximum pressure	23,000 psi (160 MPa)
Ballistic performance
Bullet mass/type Velocity Energy 35 gr (2 g) XTP 1,200 ft/s (370 m/s) 121 ft⋅lbf (164 J)
Source(s): Cartridges of the World[1]

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Despite popular belief, the 25 NAA cartridge is not based on the 32 ACP case. It is based on a rimless version of the .32 H&R case, shortened to .745" and necked down to accept .251-inch diameter (.25 ACP) bullets. The 32 ACP case, at only .680" long, is too short for use in 25 NAA production.

The cartridge was originally conceived of and prototyped by gunwriter J.B. Wood, and called the "25/32 JBW".

North American Arms and Cor-Bon Ammunition then further developed the cartridge, and the NAA Guardian .25 NAA pistol combination for production in consultation with Ed Sanow.

The finalized cartridge and pistol were introduced at the 2004 SHOT Show.^[2]

It followed the successful introduction of two other commercial bottleneck handgun cartridges, the .357 SIG in 1994 (which necked a .40 S&W case down to accept .355 caliber bullets); and the .400 Corbon in 1996 (which necked a .45 ACP case down to accept .40 caliber bullets).

According to NAA's website, the .25 NAA's 35 gr bullets travel faster (1,200 f.p.s.) and hit harder (20% more energy on average) than larger, .32 ACP caliber, bullets.

• .32 NAA
• 5.45×18mm