I thinking about building a 6x45 ar-15 . Is the faq on this gun build somewhere on the net?
I a correct the only difference between .223 and a 6mm is the barrel?
Do you have any feed issue with the gun?
I am thinking abou building a 6mm mostly because it would be more accurate than a .233. I am I correct in this assunption?

Barrel only.

The 6x45 is a .223 case necked up to a 6mm/.243 caliber. All components are swap-able with the .223/5.56mm NATO, you just need a new
barrel for the change over, in your case a 6x45 (6mm-.223) chambered barrel to swap with your exsisting .223/5.56mm.

Good luck.

My 6x45 has been very accurate but I really haven't even wrung it out that well yet.  Check your PM's.

I've owned no less than 4 6x45's AR's over the years......also had a Remmy 700 chambered in this cartridge and currently have a Savage 10 chambered in this wildcat.  In the AR platform its just a barrel swap. Although you are hindered by the magazine when seating bullets to the OAL.

IMHO the 6x45 shines with bullets in the 80-85 weight class.......for hunting I use the Barnes 85 grain tsx and Nosler 85 grain partition. 27 grains of BLC-2 is about what Ive used with either bullet for years. For general paper punching I use the Sierra 80 grain blitz king. Bullets of a heavier weight are best served in the .243 Winchester platform. 1x10 twist will stabilize the aforementioned bullets.....although I see some barrels are being rifled with a 1x9 twist...........

My last project was completed using a barrel from Black Hole Weaponry.........very nice barrel and well made.....Ive used barrels from Oly arms and ER Shaw..........

What kind of velocities are you getting in the 6x45?

Anything need to be done to the brass besides necking it up?

Its a simple neck up thats it.  I haven't even really wrung it out but If memory serves it was 2828 fps with 85 grain sierras.  In a 20 inch barrel

Does anyone know about Black Hole Weaponry's 6x45mm poly rifled barrels and their quality??

The BHW barrels are definitely Good To Go. I use them for all my AR needs....

I for one dont load hot.........as I recall I was getting in the 2700's with 80 grain bullets with a 20inch oly arms barrel......I am running a BHW 6x45 poly barrel.........very nice.......accurate.........

I bought one in 18" with a rifle length gas system, 1-9 twist.  It looked good but I did have some minor issues.
- Large burr in the bore at the gas port location.  I knocked some of it down with a bore brush.
- Barrel threads out of spec.  I could not screw on a flash hider by hand and had a lot of resistance with a wrench.  I decided to buy a die to clean up the treads.
- Gas port not quite large enough.  I had major function issues with several different loads on a rifle lower.  Gas port diameter as delivered was .102".  I opened the port to .109" (my next larger drill size) and now it functions fine.

That being said overall I am satified and I would buy another.

If you build one I would suggest the RCBS AR series dies.  I got mine from Midway for less than $40 and they work great.

I like the scenery........what bullet weights? powders are you using...........curious

Thanks!  One of the things I love about living out here is the wide open spaces.

This is my first 6x45 so I'm still playing with loads.  I built my 6x45 with the intent of shooting heavier bullets than normally shot in the 5.56.

So far I've tried 70 to 87 grain bullets from Sierra and Hornady.  My goal is to find an accurate load with the 85 grain Sierra Game King or 87 grain Hornady Match HPBT loaded to mag length.  I've had the best luck thus far with IMR 8208.

I've only used Winchester 748 and Hodgdon BLC-2..........I normally use the 80 grain Sierra blitz for paper punching.........works well in my bolt gun as well.......

I am currently in the middle of my first 6x45 mm upper build and will be using an 18" standard profile SS BHW for my barrel selection.  I have one on my 6.5 PCC upper and could not be happier, it is probably 'the' most accurate barrel I own on any of my rifles (besides my Tikkas).  I would agree with the one poster who suggested the RCBS AR dies and when I get an opportunity, will also be sending Lee a blank for an FCD in 6x45 mm because I crimp everything (although the RCBS has a taper crimp built into the seater die).  My powder of choice so far appears to be either H335 or H322 and will more than likely be shooting 55 gr to 85 gr flat based bullets, but will be trying others just for the pure fun of doing it.  I am thinking of leaning towards the H322 due to the fact that it is an éxtreme' powder and I live/ shoot/ hunt in temperatures that vary from -35 F to 90+ F.  Going that route, I will only lose maybe 50 to 100 fps or less depending on load.  The reason for the use of the flat based bullets is because of case capacity.  While experimenting with loads for the 6.5 PCC, I noticed that I could get a little more powder in than when using the BTs and getting better down range velocity.  Also, if you can get a hold of an HK 416 magazine or a PRi 10 rd magazine (unless your state does not have magazine restrictions) get them because you will be able to load out to 2.300" OAL and get a little more out of the round instead of being handicapped to 2.260" OAL (doesn't sound like much, but when you get to shooting and chronographing, it adds up).  Another build I will be doing in the 'near' future, will be a 20 Tactical in 24" barrel, that way if I find myelf in the middle of a P-Dog apocolypse, I can swap uppers and not get over heated.