I have a few of the newer 69 gr. Sierra Tipped Match King projectiles. Because they are .10" longer than the standard 69 gr. Sierra, there seems no way to load these for magazine length.

Just load them long and single feed them?

Have you tried different magazines to see if they fit?

https://sierrabulletsblog.com/2016/04/20/seating-concerns-with-sierra-tipped-matchking-tmk-bullets/

You can single load for offhand, I guess. I wouldn't bother at 600. Using 69s, I mean.

Seat them to COL <= 2.260" OAL and they will fit.

You can load them mag length, no problem.

I have a couple of the 20 round Stainless Steel CMI mags. I like them because they are thin-walled and drop free from the receiver easily by their own weight. Good idea, maybe I should try it with TAC.

I purchased the 69 gr. Sierra TMK's because of the higher advertised BC and wanted to try shooting them across the course, hoping I could use them at 600. I figured they would be longer, just not a tenth of an inch longer. I would like to be familiar with shooting a magazine length round at the normal distances in Highpower and become aware of the ballistics and not just with an 80 gr. Sierra at 600.