flashman wrote:Well thanks In2 had a theory with the crimp giving it time for the pressure to rise and all the powder given a chance to burn , giving me a cleaner burn we are talking nano seconds....
or well I could be wrong ............
AKA "shot start" - indeed ignition can be altered through the use of a crimp. This is particularly relevant for lead bullets as they are much "slipperier" than jacketed, and tend to exit the barrel sooner, demanding a faster powder or perhaps accelerated ignition. Also, if gettting close to lands is an impossibility (either due to magazine-length limitations, or perhaps just the design of the action/chamber) increased shot start
might yield better accuracy, I stress the word
might here, lots of annecdotes fly about. Some of my service buddies seem to think various service rifle design needs crimping for accuracy, for this reason (big jumps to the lands) - I'm still on the fence about this. May or may not be true, but I'd rather inherently tighter-tension over a crimp.
But you can also improve ignition through perhaps the use of a magnum primer, or think about other ways to increase inherent neck tension. One "hack" way I use to increase neck tension is to get myself a Lee Collet die and polish down the mandrel a thou or three as needed (in a drill with fine steel wool and polishing compount). You can even get offically undersized mandrels from flea bay, or just get a spare if you want to retain the original mandrel that shipped with the die. All my Service Rifles go through the Collet using undersized mandrals because as I said, a quick fire event is hard on the cartridges and I want to prevent any bullet set-back.
Then there are all the fancier dies, like the Redding bushing dies - which work great at precisely controlling neck tension. But they are expensive and couple you to a certain brand brass. You can make very accurate ammo without them.
But then my Target Rifle (single feed) is a different story. I don't use an undersized mandrel - I just bog standard mandrel and I'm only Collet Dieing lightly to minimise brass runout - neck tension is light and consistent, which comes from a combination of things a) brass annealing 2) good quality brass 3) FLS to achieve neck tension
Food for thought. In2.