I just bought 2 New 1911 Kimbers, I am going to reload my own shells,can anyone recommend the best and cleanest powder to use,any help would be much appreciated
Get a reloading manual. Lee (2nd ed.) and Lyman (49th) are good. At this time, the situation in handgun powder availability being what it is, you will be looking for 'useable and available', never mind 'best and cleanest'.
As pressures increase, even "dirty powders" clean up quite a bit. Pressure wise, the .45 acp stops where other cartridges are just getting going. Some powders are better than others though. I use mostly Bullseye and Unique for my .45 acp loads, which are ancient and fairly dirty powders. Add cast bullets to the mix and things get pretty gunky looking.
But who cares, cleaning a 1911 ain't hard, and it's therapeutic to boot.
As previously noted, what you use will come down to what you can get your hands on. Fortunately .45 acp works quite well with a huge variety of powders.
"Best" is a relative term. Best at what?
Too many variables to quantify a logical
I believe what your interested in is effiency.
Study a reloading manual such as these kind
Folks have mentioned. Look for a correlation
In working pressure and velocity. You can apply this
Knowledge to the components you have.
I'm using IMR 700x for 45ACP. It's running pretty clean and I don't have any complaints. +1 to everyone on the reloading manual and that ymmv. Everyone is looking for different things in a powder (availability being high on the list lately), so best is pretty arbitrary.