I don't shoot Benchrest with the .223, I shoot Service Rifle, but I like Winchester regular primers in the AR. I don't usually like CCI in the .223 AR, but there's one load using 52gr match bullets, 26.5gr 748 and CCI primers that shoots fantastic groups for me.
The CCI #41 primer mentioned above is supposed to be harder than usual, and is supposed to be magnum strength. Lots of people suggest magnum strength primers for Ball/Spherical/globular powders, but I have not found that necessary with the Ball/Spherical/globular powders I usually use (the one I have found it helps with is super slow WCC860). YMMV.
Lots of people like a really hard primer for semi-autos that don't have a firing pin retraction spring, such as the AR. I don't know if your friend is using a bolt or semi-auto rifle. I've always paid close attention to getting primers slightly below flush, and never has a problem with Winchesters. Heck, I used to use Federals, and never had a problem, and they're thought to be the softest and most sensitive.
Here's a link to loads used by Service Rifle match shooters (they shoot out to 600yds), using a range of bullet weights: