No, your friend is misinformed. I think he confused the National Service Rifle Championship calibers with the Wimbledon & Leech.
Years ago, Springfields & Garands were prevalent (.30-06) in service rifle matches. When the M14/M1A came along, they dominated for years (.308). Once better bullets were developed for M-16s/AR-15s, they have become tough to beat due to reduced recoil & good accuracy out to mid-distances. The service rifle matches are shot from 200-600 yards.
To clear up the confusion, I'll give you an overview of the Wimbledon & Leech Cup matches. Both are shot at 1,000 yards. I shot in both last year & will do the same here in two weeks.
There are many, many different calibers used in the Wimbledon & Leech. Although 30-06 and 308 have likely won a few, I'm unaware of ANY Wimbledon or Leech Cup won with a 223. There are actually 3 different sub-matches going on in each.
During the Leech Cup, there are trophies for high service rifle (AR-15/M16, M1A, Garand, etc), high Palma rifle (.308 caliber with iron sights), and high 'any rifle' with iron sights. The most prevalent caliber in 'any rifle' in recent years is 6.5-284. However, you will see 300 Win Mags, 30-338s, 7mm Rem Mags, etc. I shot a 7mm Remington Ultra Mag.
During the Wimbledon Cup, the same three basic categories apply: service rifle, Palma rifle, and any rifle, but scopes are allowed on the 'any rifles' in this one. 'Any rifle' shooters either shoot different rifles in the Leech & Wimbledon or have scope bases on one rifle that allow the iron sights & scopes to be interchanged.
The course of fire for each is: unlimited sighters & 20 rounds for record in 30 minutes. Shooting is done from prone at 1,000 yards with sling support only - no bipods, sandbags, etc.
The high scores from each category in each relay then wait for a shootoff. There are between 100-150 shooters per relay, so three of those 100+ will advance (one for each category). Once the shooting is complete (and after a team match), those 12 shooters will then come forward for the shootoff to compete in front of several hundred people for three very prestigious trophies. They have three sighters & 10 shots for record for all the marbles. If a tie still exists they go to a sudden death, one round at a time shootoff until somebody shoots a 9. That could take a while.
Winning scores are very high. In the Leech Cup, a perfect score of 200 is not uncommon. Since iron sight scores are typically only a couple of points lower than scope scores, it's tough. In the Wimbledon Cup, a score of 200 with a very high x-count is a must to move on to the shootoff. (I had a 198-9X last year & barely made the Top 20). The winner of my relay had a 200-7X, which is unusually low, but he went on to win the shootoff & is the current Wimbledon Cup Champion.
I hope this clears up some confusion. If you go to: www.nra.org
you will find more information. Click on the 'Competitions' section on the left edge, then find the 'Natonal Matches' or 'Camp Perry'. There is enough stuff there to get you started, plus you can always do a broader internet search & come up with more. Good luck!