6x45 in an AR

[cfts0914]

A lot of load data out there for 6x45 (6mm-223) in an AR revolves around loading to mag length. I’m considering 6x45 for an xtc gun but it all depends on what bullet I can shoot at 600 slow fire. Since it would not be limited to mag length for that stage, what is the maximum velocity I could get with a 95 to 105 grain bullet loaded as far as the throat will allow? If I can’t get those bullets up to speed I might as well stay with 223. Thanks

 

[Jason D Hostetter]

Well, that depends on many things, what powder you intend to use, barrel length, you even have to consider the gas system, to keep from killing the brass as it rips it out and ejects it. You can have a capacity similar to 6arc when using LC brass (around 32grns h2o) and loading 2.5"+, and you can run a much higher pressure. Power Pro Varmint will get 95s over 3k fps from a 24" barrel, and 105/109s to 2800 with Leverevolution, CFE223, and AA2520. But, just like the ARC, if you want to use single base extruded powder, you'll be down 150fps, likely using Benchmark/8208xbr and N530 to get decent results.

 

[SeabeeKen]

Well, that depends on many things, what powder you intend to use, barrel length, you even have to consider the gas system, to keep from killing the brass as it rips it out and ejects it. You can have a capacity similar to 6arc when using LC brass (around 32grns h2o) and loading 2.5"+, and you can run a much higher pressure. Power Pro Varmint will get 95s over 3k fps from a 24" barrel, and 105/109s to 2800 with Leverevolution, CFE223, and AA2520. But, just like the ARC, if you want to use single base extruded powder, you'll be down 150fps, likely using Benchmark/8208xbr and N530 to get decent results.

N-530 was discontinued.

 

[Jason D Hostetter]

You can still find N530 here and there, although I find it completely unnecessary, I've found that N530 produce near identical results to most lots of H4895, or some slower lots of 8208xbr. You could even get away with the 6arcs favorite powder, leverevolution, but I suspect only with 105-110grn bullets and it would be fairly compressed. 31grns of that, in Alpha brass, with CCI 450s and 105 hunting vlds, gives me 2990fps from a 27" Shilen/Kauger bolt action 6arc. 30.7 is my go to for accuracy though, shoots the 105s at 2955 avg and just does hold a single digit SD of around 8.6 usually, and shoots high .1s low .2s, does equally as well with 109s, but the average slows to 2939. I figure a similar combo, albeit, around 29grns, in a 6x45 with a 24" barrel and ~62k psi would put it in the 2830-2850 range. Carefully of course, because I've never tried leverevolution in the 6x45, I've heard from others that it does work pretty well though. I no longer shoot the 6x45, I shoot a 30" 223 and then skip to the ARC and BR, I also shoot the 224lbc and 22GT, but those pressures will kill an AR15 bolt, and the 22GT will kill brass at those pressures, probably even with +3 gas in an AR10.

 

[HandgunHTR]

IMR 8208XBR and AR Comp are the two powders that have given me the best results across a variety of bullet weights in my 6X45 AR. Mine is an 18" barrel with a rifle-length gas system, adjustable gas block and I run it suppressed.

The heaviest bullet I have used is an 87 grain Sierra because I do load to mag length in ASC mags (a bit longer than others), and I don't want to window them. I have gotten them up to 2650 out of that barrel, but my accuracy load with those bullets is down around 2610 using AR Comp.