Like its larger brother the .308 Winchester, the 5.56x45mm/.223 Remington cartridge has been used by wildcatters since its inception to create new and interesting cartridges. Since the 5.56 is already a .22-caliber cartridge, necking it down hasn’t really been feasible until recently. But necking it up to take larger-caliber bullets has been practiced for a while. One of those necked-up variants that has enjoyed some degree of popularity over the years is the 6x45mm.
As the name suggests, the 6×45 is just the 5.56×45 necked up to accept 6mm-diameter bullets. That allows for a few things:
- Increased muzzle velocity with the same bullet weight;
- Use of the cartridge to hunt deer in states that ban hunting with .22-caliber cartridges;
- Development of a popular target and hunting cartridge; and
- Use of standard AR-15 magazines and bolts.
Because of the increased bore diameter of the 6×45, bullets of the same weight will travel faster in the 6×45 than in the 5.56×45. Use of light 50- to 60-grain bullets has long been popular in the 6×45 not only for target shooters such as benchrest shooters, but also for hide hunters looking to shoot foxes, coyotes and other fur-bearing animals. Light 6mm varmint bullets have a great reputation for blowing up quickly inside their targets and not damaging fur and hide.
Because of the 45mm cartridge case length, and because magazines for many 6×45 rifles comply with the 2.26”-2.30” maximum length found in AR-15 magazines, the 6×45 can’t be loaded with many of the longer, heavier 6mm target bullets that have come into vogue recently. Those wishing to shoot those bullets in the 6×45 will have to single load them.
Especially for those shooting the 6x45mm in AR-15 rifles, the heaviest bullets available are generally around 85 grains. Only a handful of heavier bullets are capable of being loaded to magazine length, including the now-discontinued 90-grain Sierra GameKing full metal jacket, the 95-grain Nosler Ballistic Tip, and the 100-grain Speer softpoint.
Ballistics for the 6×45 will range from a 55-grain bullet at 3,500 feet per second to a 100-grain bullet at 2,600 feet per second, with that performance coming from a 24” barrel. Muzzle energy is around 1,500 foot-pounds, slightly higher than the 5.56×45, and perfectly adequate for personal defense. With the right bullets, hunting deer can be accomplished pretty easily.
As with many more obscure cartridges, the major knock on 6×45 is the lack of ammunition availability. The 6×45 has had periodic bouts of popularity throughout its history, with the last big boom occurring about a decade ago. That was the last time 6×45 AR-15 barrels and ammunition were readily available.
As of right now, there is essentially no 6×45 ammo available anywhere. If you were to find some, it would be much more expensive than 5.56×45, which makes 6×45 essentially a handloading-only proposition.
If you’re willing to take the time and effort to handload 6×45 and build your own rifles, it could provide better performance and more versatility than 5.56×45. But if you’re looking for something cheap and easy for home defense, 5.56×45 may be the better choice for you.
This article was originally posted on Red Tea News.