question about load Discrepancies

[jnestle]

I am new to reloading and been doing my homework and have purchased my equipment and supplies needed to start the journey. I subscribed to Loaddata.com and have bought other manuals as well. I want to start reloading 40 cal for a Springfield XDM.
My observation is I am finding load data discrepancies for the bullet (Nosler 135gr JHP and Powder (Alliant Bullseye) that I have purchased. Example:from Nosler data it shows a maximum load of 6.4 whereas the data from Alliant shows a max load of 7.6. I realize I will not start with a max load but, logically,the descrepancy follows down to the starting load as well. I assume I would want to start with the smaller load suggested by Nosler in that it is smaller than the Alliant starting load. I just want to be safe and sure. Any suggestions would be appreciated!

[1911rocks]

The old method prior to the Internet and higher levels of disposable income was:

1) Buy a loading manual and a Chronograph
2) Decide what Velocity/ Energy that is acceptable for your purposes. (not attainable? Get a more powerful caliber)
3) Start at the minimum and work your way up to attain the desired Velocity/Energy (10% increment)
4) Stop when Desired levels are obtained or when you see signs of over pressure.
5) If Over Pressure signs are observed reduce that load by 10%

[.284]

Not a big deal. It is very common for different manuals to vary their loads from others. Some sources are just a bit more conservative than others. Look and see if the test gun/ barrell length differs as well, I'll bet it does. Also, your are correct to start with the minimum published load and work up.

Good luck, Jeff.

[Unclenick]

There seems to be at least one active thread per month on this topic, so I have the created the following canned answer to paste into posts:

You will not be shooting the same guns the manual authors used, nor will you be loading with the same lots of brass, bullets, powders, or primers they used. All these things have manufacturing tolerances so they are not identical from one production lot to the next. The difference usually is not great, but occasionally the tolerance errors can accumulate unilaterally to cause a problem. To avoid suffering damage from this, seek out at least three sources of load data that include a minimum and maximum load. Take the smallest minimum load from among the three sources and start with that. Use Dan Newberry’s OCW method to work the load up in 0.3 grain increments to find your most accurate load. I have never run into a gun that was most accurate under excessive pressure conditions, so the most accurate load has always been a safe load, IME. But YMMV, so watch for pressure signs anyway, just to be sure.

Because of the tolerance issue, any time you run out of one of your load components and have to buy replacements from a different lot, reduce your final load 5% and work it back up again. If you have to change multiple component lots at the same same, reduce it 10% and work it back up again.