Re: Why IMR 4895 over IMR 4064 for 175 SMKs?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: SP308</div><div class="ubbcode-body">Along with this question - - a general type question -- if IMR 4895 has a "faster burn rate" than say varget of H4895-- what does this mean--
you get more velocity? <span style="font-weight: bold">It depends</span>
you get a dirtier, more fouled bore? <span style="font-weight: bold">It depends</span>
faster burn rate better for shorter barrels? <span style="font-weight: bold">Some believe that </span></div></div>
With a caliber like .308 that has a massive range of bullets it is necessary to have powders of different burn rates. Light bullets can generally use faster powders, the heavies need slower. Velocity is a based upon average pressure behind the bullet but obviously there is a pressure ceiling we are working with. As an example, if you used a relatively fast powder with a heavy bullet, the pressure curve would have a spike and velocity would suffer. On the other end if you filled the case with really slow powder, velocity would also suffer for lack of pressure. We want something in the middle that will have a nice smooth pressure curve for a high average pressure which makes for high velocities, accuracy can come with any of the above examples. YMMV We are controlling an explosion, it would be nice if we had smart powders that would just go to max safe pressure from the instant that primer was touched off and continued till the bullet exits, but that just isn't the case.