I have a 308 Bartlein 5R 1:10 Sendero profile blank. I think that its 29" long. I believe it will finish heavier than you desire though. If interested I can look closer.
It needs to be cut out some at the front of the box at the half moon cutout. It was higher than the feed ramp. Also, the follower seemed to short. I ended up with a Rem 223 factory set up and it is working fine. I just didn't take time to work with it after I found the OEM parts.
I just bought this, and it didn't work for me. It won't have the trigger guard and floorplate. It is Wyatt's box, follower, and does include the spring that is not pictured. $50 shipped.
https://wyattsoutdoor.com/product/223-kit/
I just finished pillar bedding this one. Muller barrel and custom 700 action not by me. Timney two stage trigger. Scope, bipod, and muzzle device not included. $1250 shipped. If interested I can go into more details.