The Lyman 45, 46 and 47th books say to use CCI 450, BUT . . ,
If I understand your concern, it is over ignition. Ball powders are supposed to be harder to ignite. Because I've been such an advocate of using 26.5gr 748 with regular CCI-400's, not the magnum 450's, I pulled out a bunch of my reference articles concerning 748 & CCI primers that I could find quickly. I wish I had more recent articles to share.
Harvey Bellamy's "The Seven-Inch Twist AR-15" (Rifle #103, January-February 1986, page 16) uses CCI 400 and 450 (as well as Remington 6.5 and 7.5, Federal 205, and Winchester WSR primers) with several powders, including 25-26gr 748 and 52 and 53gr Hornady bullets. Using these lighter charges of 748, 3031, 4320 and H335, he said he'd always used CCI 400 before, but based on his tests he was switching to WSR's.
Al Miller's "AR-15 Match Loads" (Handloader #67, May-June 1977, page 30) uses CCI primers, 27gr 748 with 52gr Sierra HPBT and 53gr Sierra HP's. He did not specify whether they were magnum or not (p 54), but did specify not to use a hotter primer or pressures would be higher (p 56 at end).
Ken Waters' "Pet Loads" (Handloader #85, May-June 1980, page 23, at 24) was for loads fired in a bolt-action rifle, not a AR, and I worry about some of his loads in an AR giving excess gas pressures at the port, causing too vigorous AR cycling. He used the CCI BR-4 (match, but same as 400) with 25gr 748 and the 53gr Hornady, but uses the CCI-450 with 55 grain bullets and well more than 26.5gr of 748.
Winchester's data for 748 says use a standard Winchester WSR primer with 748.
One is wise to look into this concern. After firing several thousand, I've never had ignition issues with 52gr SMK/26.5gr 748/CCI primer, even at temperatures down near 10F. The discussions over on the National Match board also do not mention any ignition issues:
http://www.nationalmatch.us/forums/index.php?showtopic=694&hl=ball powder&st=0
Actually, I don't like CCI primers, and other than this load, I've never heard of anyone using CCI primers of any sort to shoot Service Rifle. Zediker's "The Competitive AR-15" says the same thing about CCI primers. That being said, this load works.
