Do NOT mix headstamps…EVER!
Why not? I do all the time *except* when loading maximum pressure loads, such as for self/home defense or hunting loads. If you are using a mid range load, the difference between various brands of brass should never be enough to increase pressures to any noticeable degree.
If I'm loading max loads I always use same brand brass and work my way up in steps to get what I want from any given powder/bullet combo.
The only potential scenario where you might not want to mix head stamps is when there is military brass included. I usually just use military brass for low to mid range practice loads as the difference between military and commercial brass can be substantial. Personally, if I have military brass in the mix, I always develope the load with military brass. Commercial brass with the same load might chronograph a bit lower but will always be safe. One thing, you will seldom get the best accuracy out of military brass!
If you're going to try and squeeze the last bit of accuracy out of your rifle, start with Lapua brass! Maybe ADG, although I have never found any available from any source. I've been trying to get some Lapua .223 brass for a couple of years with no success but that will be used in a heavy barreled AR that already shoots pretty small groups.
Using the word "never" in a reloading context is something that should be avoided! Unless you're talking about exceeding the maximum book loads by virtually any degree. There is almost always some kind of exception! Almost, but not always! This is where experience comes in. Too often people use the strength of modern firearms to protect them from themselves! It will never pay off in the long run.
While I say "never" use just one manual, I have violated this when there is only one single source of information available for a given powder or bullet. In general, you can use load data for a specific bullet for a bullet *of similar construction* of the same weight. Where this will NOT work is when you have data for a cup & lead core bullet and you are using a mono bullet (e.g. all copper) even if the weight is the same. Another one that is claimed to be different when it comes to powder charges is the Speer Gold Dot. I will take Speer's word for this and use their data for their bullet as there are few other sources specifically for Gold Dot bullets. Beyond that, always start with a low or mid range load and work your way up to maximum loads. Or most accurate, whatever you are looking to get out of your firearm!
Lastly, another good source of reloading data is powder manufacturers websites. While I much prefer a book in front of me, there is still valuable data to be had online from numerous websites. However, do be careful where you get your info! Using a load that some guy on the internet gave you is not a good idea unless you can confirm it safe with data from a loading manual! Sometimes a guy who only shoots 2 rounds a year can get away with way overloading a cartridge without blowing the bolt back into his forehead! You might not be so lucky!
Cheers,
crkckr
