223 build.

7.5 twist here with a PTG 223 Match reamer, in a 26" Hawk Hill Marksman contour barrel. I've got a few thousand down the pipe, but I am still launching 80 ELDs at 2900fps with no issues or pressure signs from WCC brass with Varget and FGMM primers. With Federal commercial brass I had them going 2975, again with no pressure.
 
Yea, 7-7.7 twist is perfect for that sort of stuff. I have a Bartlein 7.7 twist on my RPR and it will shoot sub-MOA with most 68-80gr loads no problem without much load workout.
 
What twist and chamber are folks using for 223

Looking to shoot 73-85gn bullets
Mag fed

Since no one else has yet, using the heavies at mag length is a losing proposition. Save yourself the trouble and single load, properly seated, 80 and up bullets, unless you have mags with long enough of an internal dimension. A few of those lighter than 80 also need longer than regular mag length seating.
 
Since no one else has yet, using the heavies at mag length is a losing proposition. Save yourself the trouble and single load, properly seated, 80 and up bullets, unless you have mags with long enough of an internal dimension. A few of those lighter than 80 also need longer than regular mag length seating.

Considering this is the bolt action forum, not gas gun, 'mag length' means something completely different here than in an AR - assuming OP didn't post in the wrong forum by accident. 223 bolt gun mags allow a MUCH longer OAL than AR mags.