greyling22
Member
so I've been struggling a bit with leading in my 9mm. I'm pushing a pretty hard 124grn .356 lead bullet about 950 fps with liquid alox as lube. (bullet is dropping a true .356, and I slugged the bore out to .356 as well) I get some leading that is following the rifling down the barrel. According this http://www.lasc.us/Fryxell_Book_Chapter_7_Leading.htm
" Streaks, following the rifling: If the leading is seen to "follow the rifling" (i.e. streaks that twist down the barrel in close association with the rifling grooves), then this is a tell-tale sign that the bullet is cast too hard and failing to obturate. Obturation is usually thought of as a plastic deformation that swells the bullet's diameter, but it also leads to a back-filling of engraving defects along the trailing edge of the land. If the bullet is cast too hard to obturate, these defects will not be back-filled and gas-cutting will take place through these voids, following the trailing edge of that particular land. This effect can be mitigated somewhat through judicious choice of lube, but lube by itself can only do so much. The real solution here is to go with a softer bullet and a better lube."
you cast bullet wizards, does that seem right to you? if so, I'll try a softer bullet, double coat with alox, and push it a little faster. or some combination of the above. I'm using 4.4 grns of 3n37 as powder. I started out using red dot, but I was getting keyholing, so I went with a slower powder/harder bullet combo and the issue went away.
" Streaks, following the rifling: If the leading is seen to "follow the rifling" (i.e. streaks that twist down the barrel in close association with the rifling grooves), then this is a tell-tale sign that the bullet is cast too hard and failing to obturate. Obturation is usually thought of as a plastic deformation that swells the bullet's diameter, but it also leads to a back-filling of engraving defects along the trailing edge of the land. If the bullet is cast too hard to obturate, these defects will not be back-filled and gas-cutting will take place through these voids, following the trailing edge of that particular land. This effect can be mitigated somewhat through judicious choice of lube, but lube by itself can only do so much. The real solution here is to go with a softer bullet and a better lube."
you cast bullet wizards, does that seem right to you? if so, I'll try a softer bullet, double coat with alox, and push it a little faster. or some combination of the above. I'm using 4.4 grns of 3n37 as powder. I started out using red dot, but I was getting keyholing, so I went with a slower powder/harder bullet combo and the issue went away.