Winchester 748
This power is ideal for 55-77 grain bullets. 
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Winchester 748
This is Ball powder.  But it has a slower burn rate in 223.  This has a similar, we would say, burn tate to Varget or Reloader 15, except its a flattened ball powder, not a stick powder.  I would think its a little faster burning than say AA2520 or CFE223, and slower burning than AA2230, 2460 or H335. 

We like this powder, and think its very versatile for 5.56.  It can do it all.  It showed consistent accuracy across a variety of loads and bullets.  It was high velocity as well.  It meters great. 

You would be doing well if this was the only powder you used for 5.56, it is good at everything.  Not the best, but good enough we think...
Brass
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Some pressure signs, minor, started to show up 24 grains of Hornady 75 Grain BTHP Match, and also 27 grains of 55 grain Berger Match.  But very minor.  We would shoot that all day, its OK for us. 
It was 90 degrees out during this test.  Gun was super hot.  Didn't matter, it just kept grouping tight over and over.
Winchester 748
Good performer overall.  A lot of groups in the .2-.4 range.  Remembert, this is 50 yards.  We convert to MOA below...  What makes this powder good, perhaps, is that the 26.1-27 grain loads in the Berger 55 Match bullets, all had basically the same point of impact.  That is really good trait.

Some of the Loads we tried
Load at your own risk.  What we load doesn't Blue highlighted rows are commercial, premium bullets for comparison.  Good velocities.  Very good Standard Deviation, this is a very good powder you can be happy to own and use for 5.56.