Winchester 748 with Sierra 40 gr soft points in .223?

Sierra's 50th anniversary edition.
Sierra 40gr Soft Point (Hornet Bullet) Cartridge OAL 2.125"
Sierra 40gr Hollow Point Cartridge OAL 2.175"

Powder: 748
Minimum: 26.6gr 3100 FPS
Maximum: 28.2 3300 FPS

The use of the 748 powder really limits the range of velocity but it is usable. The test rifle was a Colt AR-15A2 HBAR with a 20" 1:7 Barrel. My best accuracy loads with the really light bullets around 40gr come in around 3300 FPS from my 1:7 Colt AR guns. Using 748 around 26.1 gr should work fairly well. Winchester 748 being a ball type powder I like using primers like CCI 450 or CCI #41 which are both small rifle magnum. While I doubt it is necessary I still work my loads up using ball or spherical powder using magnum primers.

Ron

Be mindful that 748 is temperature sensitive. Loads developed in cool weather may prove excessively hot in warm weather.

I have used 748 with good success with both 40 and 45gr. bullets. My Vanguard bolt rifle shoots the 40gr Hornet bullets loaded with 748 with great accuracy. This rifle has a slower twist rate and shoots most bullets under 55gr. very accurately.