6mmx45 or 6mm br in ar15 platform. What to do?

[robescc]

I am staring a build for my own custom ar15.  I want something out of the ordinary.  I can't decide if I want to go with the 6x45(necked up .223 brass) or a 6mm br.  I have read a few articles that say the 6mm br cartridge does not feed well in auto loaders but other people say it's great.  Any ideas?  I will be using it for a target/varment rifle.

[mkcj]

You might find this site helpful for the 6BR load.

http://www.6mmbr.com/index.html

[robescc]

I am aware of this site.  I have read about every page.  I was looking for opinions from guys who have had experiance with 1, both calibers and 2, in an ar platform.

[AWS]

No experience with them in a AR but have a great little Rem 600 in 6x45mm and it won't ever get sold.  The 6x45 should work great.

Too bad your restricted by mag length  a 6mm/204 is a great round also.

AWS

[robescc]

I have looked at the .204 ruger. I believe from what I have read that crtridge will work in the ar15.  I have seen  few companies that offer that caliber.

[AWS]

When you go to 6mm the bullet length gets to be a problem as they would have to be seated so far into the case that you lose whatever you gain by using the 204 case.  my 6mm/204's are running 2.40 with  55gr BK's.

AWS

[robescc]

That's a good point.  Thanks AWS

[CastleRocker]

I don't know if you have looked into it or not, but if you really like the 6mm, you may want to consider the 243 WSSM.  I don't have one personally, I do have a 25 WSSM, (only because that's what was for sale when I was looking for the 243), and it feeds great, shoots unbelievably well, and with the upper I have, there is very little recoil or muzzle jump.  Ballistically, my 25 is between my 257 Roberts and a 25'06.  It just has a much quicker follow-up shot!  Magazine followers need a bit of modification, but they work well. 

You might pm Rainshadow, as he has one in 243 WSSM and just shot a cougar with it.  They are a little "different" when used in an AR, but you can still buy factory ammo in a pinch.  Just a suggestion. 

I still have my 6.5 TCU barrel for my contender from the silhouette shooting days, and it is still one of the most accurate firearms I own.  I've been thinking about a new upper myself that would be a little different...hmmm