From the sound of it you are using a 1-12" or 1-14" twist barrel in your rifle. In that case I wouldn't bother with the 55s. Especially if you are shooting primarily 300 yards and in.

Some folks will tell you that the superior BC of the 55s compared to the 40s mean less drop at 300 yards. That would be true if both were fired at the same velocity, however the 40s can be launched at substantially higher velocities. Since drop is purely a function of time of flight the 40s win out to 300 no problem. As far as varminting goes to 40 will do anything a 55 will.

My pet load is a moly coated 40 gr Nosler BT, a Lapua case, Winchester primer and either 21.5 gr of IMR 4198 or 22.0 gr of H4198. The two powders are not exactly the same. Going to Winchester brass which is quite a bit lighter than the Lapua charge weights are increased by 0.5 gr. Muzzle velocity runs about 3600 out of a 26" barrel and about 3550 out of a 24" barrel. Since it is a comparatively mild load barrel wear is very low. This load is very similar to a favorite bench rest load from the days when the .222 rules the roost.

For shooting past 300 yards with a .223 the 69 gr and heavier bullets should be used where the higher BC will make a difference, but then you get into needing fast twist barrels.

A few years back I did considerable experimentation with the .223, testing about 750 seperate combinations of powder, bullets and primers. Took the best part of a year. What it proved to me at least, was that all of the exotic and new powders didn't prove to work any better than a classic load. If I want to go faster, I have a 22-250. But for varminting and trigger time practicing it's an ideal load, quite, no recoil worth mentioning, cheap on powder, and easy on the barrel.

After using just about all of them. My favorite is 2015.

Does anyone know if 2230C is the same stuff Jeff Bartlett was selling sometime back as "PSA?" That stuff was supposed to have been made in China under contract to Accurate as 2230, but was rejected. Bartlett said to use 3031 data. It made the most impressive muzzle flashes of any powder I've ever fired, but is mighty good shooting stuff in several cartridges that use that burning rate. I bought 8 lbs, wish I'd bought more when he had it at $56/8 lbs.

Have to agree with several others that my favorite .223 powder was Accurate 2015-BR. It gave top velocities and accuracy in a Savage 110GV, 24" barrel, 1 in 12" twist. Favorite bullet was the Nosler 50 gr Ballistic Tip with CCI BR-4 primers, winchester brass. Tried most of the others, 748 was so-so, 4198 gave mediocre velocity, 2230 was not as consistent (had better luck with 2460) 2200 gave mediocre velocity. I think that Varget may be good for the heavy bullet (68 grains and up) uses, but I found nothing special about it with the 50 and 55 gr bullets.