Burn rate charts only give you a relative burning rate of powders, ie, one burns faster than another, but how much faster or slower? I have used Quickloads for four years now and that is a great computer simulation for internal ballistics. It has really helped me pick out what I think would be the best powder to use in the calibers and bullets I am using. It does mean I may have to trade or wait for the powders I want to use to become available. It will also tell me the limitations of what powders I may have available at the time in terms of chamber pressures, muzzle velocities and barrel dwell times for best predicted accuracy. For me it has been a money saver, not wasting my time trying out various powders and loads that may not be the best suited for the rifles I am load developing.
Ive been using Quickload for some years now and have made some interesting observations and put them to the test as well. I'm not trying to start a debate, just pass on a few things I've learned. Since using it, I seldom test more than 2-3 powders and that at times even less.
It is very easy to match a specific powder to a cartridge and bullet. I have also found many shooters use a powder that is far too slow, often wasting as much as 30% of it out the muzzle as a flash. For example, I recently started testing in my new 284 Win using 120 gr Barnes TTSX. Many recommended 4831 but when looking at it, I couldn't get the velocities and pressure was very low, and much of it was burned outside the muzzle as a flash. What a waste. Also, that burning and unburned powder being forced thru the barrel is like sandpaper and helps to erode the throat as well as the bore. I started running simulations on 4350, RL-16, 26 & 17 which seemed like a good fit so I found a good OBT load and made that the center load and worked out in .3 gr increments higher and lower (in case QL powder burn rate were off). Of those 3, RL-16 shot best and was reasonably efficient. Loaded up some more RL-16 to test and at the last minute, started looking at faster powders. IMR-4166 was showing to be very efficient, good case fill, nice velocity (3136) curve, and about 97% burned. Bingo! Across 4 .3 gr increases I got ES numbers, 3,4,5,6. SD numbers from 3.7 to 5.6. The best group was the load just below OBT load measuring .1". I also had a 243 that shot bug holes using IMR-3031 with 100 gr bullets. I seldom use anything anymore slower than 4350 because for my cartridges, they just aren't needed. Using this same method, I recently tested a friends 350 Legend and again .5" groups which is impressive for that cartridge. using this method on a number of cartridges, I can usually hit on .7" groups or less first trip out on my hunting rifles. Im not saying the methods of other s don't work, just that this has worked very well for me. I also use some other tricks to get my numbers low also but this post is already far too long.
Another way to help match the perfect powders to a cartridge is play with loads until you can stack the Z1 and P1 lines on top of each other. Often that is the perfect burn speed powder. As always, the devil is in the details and precise input data is the key. i.e. H2O capacity, barrel length, case length, bullet length, etc. There are other numbers to tweak as well to fine tune. QL is NOT for the novice handloader nor is it meant to replace loading manuals. Ive found that it can be way off too at times. It does remove a lot of guess work and is a huge help with wildcats that aren't in manuals. I shoot 243ai, 250ai, 257ai, 7x57ai, and 20 Vartarg and it has been a huge help. For example, during load workups on my 250ai, I wanted to find the upper limit by loading in .3 gr increments without QL. Eventually, I got to slightly stiff bolt lift and slight burnish on the case head. I punched in the data for that load in QL and it showed my pressure over 74,000 psi. I was well over pressure by the time signs showed. My method works for me every time, your mileage may vary and I apologize if I've ruffled any feathers as it was not my intention.
I don't shoot the big magnums anymore and I realize they require the slow burning powders. I'm just referring to the cartridges that I load and test.
Also, there is a free internal ballistic program called Gordon's Reloading Tool (GRT) on the web which I have not used but hear it is a good program and getting better.