6×45mm

6x45 mm
Type	Rifle
Place of origin	USA
Production history
Designed	1965
Specifications
Parent case	.223 Remington
Case type	Rimless, bottleneck
Bullet diameter	0.243 (6 mm)
Neck diameter	0.272 in (6.9 mm)
Shoulder diameter	0.354 in (9.0 mm)
Base diameter	0.376 in (9.6 mm)
Rim diameter	0.378 in (9.6 mm)
Case length	1.76 in (45 mm)
Primer type	Small rifle
Ballistic performance
Bullet mass/type Velocity Energy 75 gr (5 g) SP 2,700 ft/s (820 m/s) 1,214 ft⋅lbf (1,646 J) 80 gr (5 g) SP 2,650 ft/s (810 m/s) 1,248 ft⋅lbf (1,692 J) 90 gr (6 g) SP 2,540 ft/s (770 m/s) 1,300 ft⋅lbf (1,800 J) 100 gr (6 g) SP 2,400 ft/s (730 m/s) 1,279 ft⋅lbf (1,734 J)

The 6x45mm cartridge is the .223 or 5.56x45mm NATO round necked up to 6 mm. It is a fine small game or varmint round. It can be used in small bolt action or AR-15 type rifles. It was also tested by the US Army for a Squad Automatic Weapon.

The 6x45mm has a rather small powder capacity and will thus give best results using bullets of low to moderate weight (up to approx. 90 grains). Initial velocities are normally between 750 m/s and 850 m/s depending on bullet weight. Due to the low velocity and moderate effect on the game, it is a rather popular wildcat cartridge for small game hunting for meat.

In 1973 the cartridge set a new IBS 200yard record of 0.3062”. The cartridge could not compete with the 308 Win in match competition though and in the benchrest arena it was replaced by the 6 mm PPC. Today in the US this cartridge is relegated to the occasional varminter.

This cartridge has become quite popular in South Africa as a small game cartridge in bushveld conditions using the 100gr bullet at about 2350ft/s. At this velocity it is adequate for our most common small antelope the impala but it is also capable of handling slightly larger animals such as blesbok and in a pinch Hartbeest or Njala.

Ideal is regarded as around 2300 to 2400ft/s. At this velocity meat damage is minimised, penetration is excellent, it has sufficient range for bushveld hunting (most shots below 150 yards) and one gets reliable performance from conventional construction bullets.

The beauty of this cartridge is that you can build very small light rifles on the mini actions (the Zastava mini action has been the action of choice). Many people have fallen in love with these small rifles and the 6X45 with its low recoil is perfect for this application. It also has notably less muzzle blast than many of the “standard” calibres (243, 308 etc.)

Note, the cartridge is not just short; it has a small case-head meaning you actually use the small bolt, not just a short action with a standard diameter bolt.

There is probably no other 'wildcat', which has seen as wide application as this one in Africa and it grew to such an extent that one of our larger ammunition manufacturers started producing factory ammunition for it. This expanded its use to non-reloaders and increased its popularity further.

With the lighter bullets the cartridge can be used as a plains country springbok calibre if shots are kept below 300 yards.

Many people obtained these rifles under the pretext that it is for the wife or children (and the rifle is truly excellent for this purpose) and then fall in love with it and before long it is their preferred rifle.

Rifles for this calibre are either built on the mini actions or alternatively people simply buy a 223 and rebarrel it. People who fall in love with small rifles such as .22 Hornet etc. will understand the magic of this little cartridge.

In addition to small bolt action rifles numerous companies in the US are using the 6X45 on military and civilian semi automatic rifles AR15/M16 type. The advantages of the 6X45 outweigh most of the exotic AR15 rifle calibers due to the cost. With so much surpluss brass as well as the readily available .243 (6mm) bullets reloaders have multitudes of options when working up a load as well as commercially available ammo at prices equal to the .223 or 5.56.

Manufacturers of the Rifes are The Spirit Gun MFG. Co LLC in West Palm Beach Fl. offering variations for Military and Law enforcement, as well as consumer and sporting rifles. Ammunition is also readily available through many Retail outlets and distributors, Black Hills Ammunition is currently producing the 6X45 ammunition and is distributed through Sporting Products LLC in Florida. Ammunition is loaded in military brass and 3 bullet weights are available. 62 Grain Barnes varmint grenade @ 2900 FPS, the sierra Gameking 85 Grain @ 2800 FPS, and the 100 Grain sierra game king @ 2700 FPS. All load balisitics provided were shot through a 20" pressure barrel and are within SAAMI spec. The 100 grain bullet produces roughly 58000 CUP at 100% case capacity. Loads are available in Mil packs stripper clip loaded, as well as 50 round commercial boxes.

From a military application the 6X45 has not only downrange benefits; but substantial cost savings on the actual rifle hardware. The only change to the existing US military M4, M5, & M16 would be a barrel change. The case is the same as the 5.56 NATO and the OAL case length is the same as a 77 grain 5.56. Using the same magazine makes the 6X45 a viable contender for special security missions.

Downrange ballistics roughly increase 20% at the muzzle when comparing 77 grain VS the 100 grain bullet and this number jumps about 10% per hundred yards. When shot out of the tradition M4 carbine the 6X45 can provide infantry with long range capabilities while not being selected as a primary sniper in a platoon. The 6X45 died many years ago as a bench rest cartridge but with advances in powders and weapons platforms the cartridge has been reborn as a viable hunting round, for furry and non-furry targets.

See also

• List of rifle cartridges
• 6 mm caliber

References

www.spiritgunmfg.com www.sportinproducts.com www.blackhillsammunition.com