6x45mm......What do you know?.......

[Out Rider]

I got in a trade a 6x45mm barrel. Is this a good round, or one of those that looks good on paper but fails to produce down range?
Any one have any Ideas?.........Thanks,.........

[Colorado Osprey]

The 6x45 is a wildcat. It was originally a TC encore chambering. The 6x45 is a solution to a problem that has been overcome by the 6.8 SPC or the .300 Whisper.

It falls short of the .243, but hits harder than the .223. it would be ok for CQB or coyotes up close. It also makes an AR legal to hunt deer and antelope at closer ranges while using a low cap mag.

[Colorado Osprey]

Ok, Ok, this last post got me thinking and I had to make one myself.


I own a few .223 rifles. I use these mainly on prairie dogs. I had a new AR-15 reciever to make another one but couldn't seem to find a hole in my collection that needs filling. I already have WSSM and pistol caliber AR-15's. I thought that maybe there is a cartridge that will fit in the AR-15 platform that will buck the wind a little better than the .224 cal bullets but still be available cheaply and plentifully like the .223.

Solution: 6x45
It uses standard .223 brass just necked up to accept the 6mm/.243 bullets. This means just a barrel change in any standard Ar-15 and I'm in business. I am building one just for this caliber though. Intersting enough the lightest bullet weight that I load (70 grain) in .243 loaded in a 6x45 actually is equal in energy and speed to a 22-250 in a 70 grain. That means I'm not shooting an AR-15 with the velocity of a 22-250 without changing anything other than the barrel. even standard mags work.
Now that same 6x45 can also be loaded with 100 grain bullets, something not possible with the .223, and used to hunt coyotes in stiff wind, even smaller deer or antelope.

Will my .243 do this and more? Sure, just not so economically. The .243 uses the same bullets and powder as the 6x45 but just about 10 grains less powder and brass is waaay cheaper.

[Out Rider]

I've been listening and now I'm getting Antsy about getting mine together,.....

[Colorado Osprey]

Let me tell you a little more:
I had believed that the round was originally developed by TC for the encore pistols...upon further inverstigation...that cartridge is just a little different. It is called the 6mm TCU and is loaded lighter and has a different shoulder than the 6x45.

The 6x45 was originally developed for the US Army in it's development of the M249 SAW as something with a little more range and energy than the 5.56 In testing the cartridge proved itself...but the military in it's infinate wisdom chose not to pursue it and instead used the standard 5.56 to keep logistics simpler.

With the same weight bullets as the 5.56 it will shoot on average 2-300ft/sec faster because of the less bearing surface per weight when shooting in larger caliber. This also allows for more case volume too. When shooting the same lenght bullets the velocities are almost identical to the 5.56, but it is shooting a larger diameter and heavier bullet which in turn gives it about 20-30% more energy on target at any given distance.

The beauty of this cartridge is either shot out of an M249 (like we all have those) or any other 5.56 platform...all that is required is a barrel change.

Here are a few pics of the difference in loaded ammo and brass.
223 vs 6x45 brass and loaded ammo
http://i88.photobucket.com/albums/k175/ColoradoOsprey/DSC04164.jpg
Top view
http://i88.photobucket.com/albums/k175/ColoradoOsprey/DSC04165.jpg
.223 vs. 6x45 vs. .243
http://i88.photobucket.com/albums/k175/ColoradoOsprey/DSC04167.jpg
The 6x45 has also seen a lot of popularity as a bench gun. It still holds many accuracy records...but most are over 15-20 years old. With the advent of the PPC and BR 6mm's the 6x45 has lost it's populartity as a bench gun but is still favored by varminters for something with more reach and heavier hitting than a .223 but less than a .243

Barrel life is considered excellent and most barrels actually outlast .223 barrels as far as throat erosion.

[Colorado Osprey]

Here's my 6x45 rifle:
http://i88.photobucket.com/albums/k175/ColoradoOsprey/Dsc04237.jpg

[Out Rider]

The actual round that paralleled the development of the M249 was called 6mm SAW, it looked more like a 5.45x39mm round. The slug weighed 105gns and run at about 2500fps,....XM732 Ball. The 6x45 is what they ended up with but it started out as a 6x51(243Win.?) and they even experimented with basically a 17 Remington too(4.32x45),.... can you imagine the problems there.........

Good Read Here,...... http://www.thegunzone.com/556dw-2.html