223 reloading question?

I am a reloading instructor.

I am not familiar with Benchmark. With the current powder shortage - I have been using allot of new powders this summer with some surprisingly awesome results.

40gr was the original weight bullet when the 223 Remington was hatched - but - that was a bolt gun with a 1:16 twist barrel. Almost all the guns made today are 1:9 twist or faster - so - you might not be able to get the kind of accuracy people talked about decades ago with the older rifles. It will be good - but - not 'tack driving two or three rounds in the same hole at 200 yards good'. Moving to 62gr to 69gr will do better for you. With the more expensive 68/69 grain models being the most awesome and best.

Be sure to always buy a big box of 1,000 primers when you work up this powder load. Jumping from one brand to another makes a difference in this cartridge.

They can only put so much load data on the side of a can. Be sure to visit the manufacturer's web site - I would bet money they have more data for many other weight bullets.

the can data is the most up to date for that powder lot. Adjust up and or down to get best group size. Load development take a skill level few actually possess. Look at primers for pressure signs, burn marks on the neck of the fired cartridge.

In a new modern firearm you will find max is pretty reliable for most rifles.