laker415
When you look at load data for the .223/5.56 the first thing you should do is look at the twist rate for the rifle being used for the test data. You will find rifles with 1 in 14, 1 in 12, 1 in 9, 1 in 8, 1 in 7 ect. the load data where you see 25 grains of H335 as being over max are the rifle with short throats.
Below rifles with a 1 in 14 or 1 in 12 will normally have a short throat and this is why the load data is lower. The shorter throat on the left can not be loaded as "hot" as the throat on the right and this is why you need to look at the rifles twist rate in the load data.
Below is 25 grains of H335 in a longer throated AR15 rifle, and it is 5,000 psi below max pressure and the same practice load I use in my .223/5.56 rifles. The Sierra manual lists 25.7 grains of H335 in their AR15 load data as max and Hodgdons data lists 25.3 as max for a .223 rifle with a 1 in 14 twist.
The Savage .223 rifle I have with a 1 in 9 twist has a "LONGER" throat than either of my AR15 rifles and can be loaded warmer.
Look at the link below and the first chamber listed that Savage uses in their rifles
HOLLIGER ON .223/5.56 CHAMBERS
http://www.radomski.us/njhp/cart_tech.htm
Both the .223 and 5.56 NATO are loaded to the same chamber pressure of 52,000 cup or 55,000 psi SAAMI standards and the only difference is the throat of the rifle.
Todays .223 chambers must be big enough for the cartridge and the company lawyer. And you need to know the twist rate of your .223 rifles and its throat length when reload for your rifle.
This is also "WHY" they tell you to start low and work up your loads, and again my long throated Savage .223 can be loaded warmer than my AR15 rifles.
Look at the freebore lengths below and you will see nothing is written in stone when it comes to loading data................and loading data is "ball park" information.