I'm loading some .223 plinking rounds for my AR useing 24.2gr. of Accurate 2015 and some pulled 62gr. SS109 projectiles.
Looking at the Speer #14 Manual it shows 20.5 to 22.5gr of AA2015 for a 62gr FMJBT bullet.
The Lyman 49th Edition shows 22.0 to 24.5gr for a 63gr jacketed bullet.
The Lyman shows hotter loads for most loads.
Why is that?
Am I gonna be ok with 24.3gr AA2015 begind a 62gr bullet?

Thanks

The differences in load data from each manual is due mainly to the testing equipment and methods. Plus the conditions under which testing was done can be a facter in their results.

Components used by each manufacturer can affect the results.

What results you get depends mainly on what type of rifle you are shooting. Look in the data at the start of the caliber data. Usually they list if a bolt rifle was used, if a test barrel was used or if a semi auto was used. This can give you an idea of which data to use.

You can also average or chart the different loads. Say one book shows 20 to 25 grains as a range and anothe book shows 22 to 27 grains for the same load powder. I would pick 23 grains as a start and adjust up or down depending on what pressure signs I saw never to exceed the max of 27 grains. Doing this method is long work but it can help tune your rifle to something it likes. You do not have to load to the fastest hottest speed on the planet.

Good  luck and shoot safe.

You can start 10% low from the highest number, just work up.  Stop when you reach pressure signs or your desired level of accuracy.

In my experience of developing loads for SS-109 bullets, I have always used the Speer "start" loads for their 62 gr lead core bullets.

Remember we are substituting bullets of the same weight, but different construction.

Begin loading with Speer's "start" load and work up, you will be GTG.

I have not used AA-2015, I have used AA-2230 with great results.

Different data for the "same" load is something to get used to. Happens all the time.

Get as many different sources of data as you can, study it, and make your decision on a starting charge.

Buy more loading manuals as you can.

Good luck.

on a practical basis it really doesnt matter which data you use since you will/should/must start out by making test loads, from 10% under max to the max load listed.  Test fire the loads with the smallest amount of powder and work your way up, STOP! when you see high pressure signs even if you have some test loads with higher powder charges in them.  If you do, then pull those bullets.

Why would loading ten of your SS109 projectiles in front of 20.5 grains of AA2015 be so bad? And then adding 0.5gr for the next ten and so-on until you see pressure signs?  They'll all plink and they'll all be fun !
If you look at the .223 data in your Lyman Manual, you'll see that with some projectiles, they get the most uniform ballistics with starting loads.