Variance in reloading data

General Firearms Reloading & Ammunition
1

I’m a bit confused by the variance in load data between my Lyman 49th edition manual, the powder manufacturers data, and the bullet manufacturers load data. Min and Max ranges can vary by up to 1-2 grains of powder in some instances:
Which would you trust more out of all the sources and why, and is there danger to starting at the lowest charge shown out of all three sources? I assume the variances are due to the differences in barrels/chambers used to develop the load data.

Here is an example in .223 using H335 powder and 69gr Sierra match kings.
My first 50 rounds I loaded were started at 22.9 per the Lyman manual, but it didn’t feel like a particularly light load in my 16" 1x7 carbine and if I went by the sierra data, I would be pushing close to max load, and if I ever worked up to mid range according to the Lyman manual I would be at max for Hogdon’s and past Max for Sierra’s data.

Lyman manual: 22.9 to 25.5 grs
Hogdon Powder Company website: 22 to 24 grs
Sierra rifle reloading data (AR-15) PDF: 21.2 to 23.8 grs

I’m more inclined to believe the Sierra data simply because it is meant specifically for the AR-15, however the Lyman data I have was also tested in a colt AR-15 20" 1-7 twist rifle. The Hogdon data’s specs mention a 1:12" twist 24" barrel configuration with a short C.O.L. of 2.235" which would indicate to me it was not meant for an AR-15 type chamber.

2

B52U,

You have to remember that the publishers of those books publish a max for those exact test conditions which you may not be exactly duplicating a la: chamber dimension variance, case capacity variance, powder lot variance, type of primer, etc. etc. So it is really no wonder that things are not going to come out exactly the same - too many variables.

I am not a reloading expert by any means, but most everything I had read on the subject indicates that this fear of undercharging with powder is mostly overdone, and relates to cartridges using slow powder (.223 uses medium burning powder, not slow) and substantial undercharges. The Lee manual has some interesting things about this, and maybe there are some other sources also. In any case I think it safe to say that if you are using substantially similar components, that you are going to be perfectly safe using the lowest published load as a starting load. Work up your load slowly from there, watching for pressure signs, and if you have any concerns stay under published max charges.

You are already ahead of most reloaders based on the fact that you are cross referencing multiple sources of load data.

Best of luck.