Boolit Base Cupping and more defects

[303Guy]

http://i388.photobucket.com/albums/oo327/303Guy/BaseCupping.jpg Base rebate stops edge drag feathering.

http://i388.photobucket.com/albums/oo327/303Guy/MVC-723F.jpg The shiny patch is from patch wear through.

The only skidding or slip on this boolit is from the patch wearing through on the driving face.

http://i388.photobucket.com/albums/oo327/303Guy/MVC-722F-1.jpg

The other side has no patch wear through making the shear wear clearer.

http://i388.photobucket.com/albums/oo327/303Guy/MVC-724F.jpg

Hear are some strange 'rifling' impressions on the nose section of this same boolit. Strange because it's a two-groove!

http://i388.photobucket.com/albums/oo327/303Guy/Two-GroovePP30grAR220957grBran.jpg

This boolit was harder and had no cupping but it did have drag feathering. The patch shear is greater on this one.

It seems that the softer the alloy, the less rifling shear occurs but then I get more base cupping.

A softer boolit.

http://i388.photobucket.com/albums/oo327/303Guy/Two-GroovePP28grAR220910grBran2.jpg No base rebate.

Here there is edge drag feathering plus cupping but no rifling shear - hard to see in the pic.

[303Guy]

I found the cause and got rid of it!

http://i388.photobucket.com/albums/oo327/303Guy/SizedCore208gr.jpg

There is no rifling shear and no patch failure and this with a 208gr boolit. The trick? size to smaller than bore diameter and patch to fit the throat. The powder and filler probably play a role too - 28gr 4350 plus 9gr wheat bran with the boolit seated with the base at the base of the neck. Final patched size - .313 tapering to .310 The patch 'confettied'.