I still have both on the shelf. I've not chronographed them side by side. I suspect that there's less difference than many make out to be.
I'd only suggest that a person take the same normal precautions he would when hand loading from a different lot of powder. This would apply mostly to maximum loads anyway.
2400 especially seems to have a reputation as being changed and is now considered to be faster. I think it's the same product. It'd be senseless in this day and age for a manufacturer to market a product radically different from recognized performance levels and represent it as the same product. Alliant is selling 2400, not "2401." They'd be courting a law suit for sure if they materially altered the burning rate of 2400 without changing its name.
I've worked back up to my chosen magnum 2400 load in my S&W Model 27 with the new stuff. It gave all appearances of identical performance and pressure signs. One of these days I'll load a batch of old and new lot 2400 and shoot them side by side over the chronograph to see if there's any major velocity differences. I imagine there's not.
A generation of Americans have arisen with the "Chicken Little" syndrome. They are frightened of their own shadows. They are scared of everything including global warming, second hand smoke, cell phone generated brain cancer, cholesterol, trans fats, tap water, sun's rays, their health insurance plan, what the Muslims might think about them, agricultural pesticides, firearms, high school sports, motorcycles without helmets, red meat, and 2400. They're not afraid at all of trading their freedoms away for some tofu and some government protection. If they live long enough they're gonna die but they seem to think they can avoid the event if they will only "watch out" for stuff that's out to get them. They also enjoy pontificating (as I am here) about what they think they know and communicating it to all and sundry in order that everyone can stew about it together.
:lol: No apology necessary. I don't actually load to the top end anymore. My Blackhawk and my Rossi 357s seem to like 14.0 of 2400 (old 2400) with Elmer's bullet. 15.0 in the handgun only gave me an extra 37 fps. I might try it again later because I didn't own the carbine at the time. It's beginning to sound to me like nothing more than normal lot-to-lot differences.
+1 on what Brian said...I couldn't have worded it any better.
I use the very same Unique and 2400 loads as I did in the old Hercules days - with basically the same velocities as before. As you say, the minor differences I've seen on the Chrony could be attributed to lot variations.
I will declare that "New" Alliant Unique is noticeably cleaner-burning than the older formula - but I never considered it to be a particularly "dirty" powder anyway.
The burning rate of these powders has not changed.
Does it seem strange that powders are supposedly always changed in the very way that would make them more dangerous? We are told that their burning rate has been increased.
If the manufacturers increased the burning rate of powders this would be a serious liability for them. Because the simple fact is that many peole don't buy the latest manual.
My tests with these powders shows only the normal lot to lot variation, which is in fact very small. In checking my notes I found that the highest velocity and greatest pressure sign with my 2400 .357 load actually came fro an old container of Hercules 2400 made in 1966. Even then I only had to adjust the powder charge down 4/10 of a grain.
I think it is safe to say that this myth of powder burning rates being increased, is just that a myth.