Different load data in Hornady vs Lyman books

Swaim13 · Dec 31, 2017

I have a Lyman and a Hornady reloading book. I am typically reloading 223 and noticed the the two books do not line up with the powder loads at all. I am specifically looking at the 75 gr BTHP round utilizing Varget powder. The Hornady book indicates a starting load of 19.4 gr and a max of 23.5 gr and a max velocity of 2600 fps. The Lyman book indicates a starting load of 23.0 gr and a max of 25.6 gr with a max velocity of 2843 fps. The only difference that I can see between the loads is the primers. The Lyman book uses Remington 7.5 primers and the Hornady uses WSR primers.

I also know that Hornady makes match grade cartridges which have a muzzle velocity of 2790 fps but I am not sure what powder is being used.

I noticed similar trends in a few other calibers and loads. Is the Hornady book just being conservative? Am I missing something in particular? Is it safe to use the Lyman numbers if I build up to them?

BradMacc82 · Dec 31, 2017

You also need to look at what type of firearm/receiver was used to develop the listed data. Lyman's 49th shows a Universal receiver with a 24" 1:12 barrel is used for pressure/velocity, but a 20" Colt with a 1:7 barrel was also used for the heavier rounds.

As always, you build up. Sometimes the listed data just isn't going to be feasible in a particular firearm/configuration. Example, the listed max load data for a 60gr Vmax in a .223 using H335 - great in a 24" bolt gun, a disaster in a 16" AR (mid-length gas).

Melnic · Dec 31, 2017

It is not unusual to see differences but that is pretty severe compared to things I've seen. You may also see changes in different revisions of the same reloading manual.
Look at the Hodgdon reloading data center on the website.
They show 22.5 - 25 (compressed) for 75gr bullets

I"ve found the Hodgdon site to be pretty darn close and at least gives me accurate starting loads. I recall 69g bthp would compress for me around 25.5gr of Varget

Doco Overboard · Dec 31, 2017

BradMacc82 said:
You also need to look at what type of firearm/receiver was used to develop the listed data. Lyman's 49th shows a Universal receiver with a 24" 1:12 barrel is used for pressure/velocity, but a 20" Colt with a 1:7 barrel was also used for the heavier rounds.

As always, you build up. Sometimes the listed data just isn't going to be feasible in a particular firearm/configuration. Example, the listed max load data for a 60gr Vmax in a .223 using H335 - great in a 24" bolt gun, a disaster in a 16" AR (mid-length gas).

Thats exactly right. Thats why you always start with a minimum load and the reasons are usually stated in the forward section. And or reduce charges a few percent when components are being substituted or changed. One firearm manufactured exactly after the first could react substantially different with even a starting load.
Factory powders are manufactured in bulk and are blended sometimes from entirely different chemicals to provide uniform ballistics throughout many lots/production runs. Some of these are trade secrets. Trying to imitate factory velocities from canister powders is hard to do not to mention that max velocity loads are not always the most consistent or accurate.
They can even be unsafe when used in arms that the load was not originally developed in.

Pinecone · Jan 3, 2018

Yeap, any change, changes things.

Change of firearm (chamber dimensions) or primer even.

Which is why you ALWAYS start with a reduced load and work up. And the Max in the book is not necessarily the Max in YOUR firearm. Your Max may be higher or lower than the book.

The OCW method of working up loads takes this into account, but making small powder changes, such that if x load is not showing pressure signs, x+1 will not harm the firearm (especially for the on or two rounds fired). And you may be able to work up beyond the book Max. BUT, only for THAT rifle.

Different load data in Hornady vs Lyman books

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