hey guys , i was curious about this some time ago . i didnt know the actual chamber dimentions of my gun until i purchased a sinclair dead neck length gauge ! now my loading book says trim to 1750 - 1760 max ! my remy 700 s/a 223 measures 1789 exactly , so i had some brass that id reloaded quite a few times (lapua) and id annealed them too and they had grown to 1762-1777 so i dicided to cut to 1765. think its worth mentioning that freshly annealed brass streaches a little bit quicker as its slightly softer ! try it if you can you just might even get tighter groups ....