So, Do the big cased cartridges we all love burn ALL the powder contained? I'm talking the STW, the RUMs and Weatherbys and bigger. OR, does some of that powder exit the barrel unburned? If you say yes, do you have proof? WHY isn't it burned? Shouldn't the newer powders available have addressed the problem if it existed? Also, if all powder is not burned, does it accelerate throat erosion? I've heard some "experts" expound upon this while bashing big magnums. What do you guys know? mtmuley
This is my belief, some powder types will burn far more efficiently than others. I agree with Michael Eichele, it's true, it happens some of the time.
An easy fix if it's happening with a single base propellant is to switch to a double base propellant that is slightly slower ie: switch H4831sc to RE22 for example.
The reason it's not burned is because the pressure hasn't risen fast enough to allow peak pressure to be reached, as you know as pressure increases so does the burn rate, and so as pressure is increased further more powder is burned quicker.
Throat erosion is caused by a 'plug' of unburnt powder moving from the brass case to the chamber throat, which is larger and longer in big cases than small ones. It acts very much like the glass beads in sand blasting on the barrel steel, and the more powder that is not burnt on initial ignition the worse it's effects will be.
Single base powders seem to be the worst for this, I'm not sure why, I think it is because double base powders release their energy quicker than single base powders, but switching to either a ball powder or double base extruded powder seems to prolong barrel life.
So to answer your question about big cases not burning all the powder, yes and no, it depends on your choice of powder and also loading technique, which by this I mean 'packing scheme' of your selected powder. If you slow drop the powder for a tighter pack or use the swirl charge method, you will get more uniform ignition and the powder will burn correctly, and lessen the chance of the 'plug' forming.
Cheers.
MagnumManiac.
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