I am building a 338-06 on a weatherby mk v action as 338-06 ammunition is not available in the UK where I am do you think a Lee factory crimp die will make my homeloads more accurate thanks in advance.
I've dabbled with the Factory Crimp a little. So far I haven't seen any significant increase in accuracy. I use a light crimp for heavier recoiling rifles as bullets can take a beating in the magazine box. A friend of mine has a couple 338-06 and loves them.
You won't get near as much bang for the buck out of a crimp die as you will a concentricity gage. I've found (as have many thousands of others) reducing runout as much as possible aids in accurate loads. The only rifle cartridge I crimp is 45-70 because it is in a tubular magazine. None of the 6 bottle neck cases I load get a crimp. I experimented with my 223 and found a taper crimp to add some value to my reloads but not enough to recommend it as standard practice. I am not a fan of gimmics or using tools to straighten ammo once it has been loaded. Some are but I'm not. To me that is analagous to putting a bandaid on an arterial wound. Not the right thing to do.
Having said that, what dies are you using to form/resize your cases?