Unburnt powder? 
Squib ?
Interesting. A squib with a light charge of W296?
I am extremely interested in the pic . Explanation please .
The sixgun is a converted Ruger Bisley in 357 Mag. The load was 12.5 grains of WC820 with a CCI550 primer. I used this charge for the first 1000 rounds though the gun with a MagTec 158 grain HP bullet. It shot lights out. The trouble came when I replaced the bullet with the NOE 360-160-WFN in hollow point form. The bullet weight is close to 158 grains but because of less resistance in the barrel the pressure wasn’t high enough for a good burn. I raised the power charge to 13.5 grains & the problem went away & hasn’t returned regardless of conditions.
Not familiar with NOE molds … so wanted to look up some history on thd name couldnt find it even on their own website . But none- the less a squib but not really a squib just an underpowered load due to too light of a charge behind a bullet with less overall mass.
So, you’re saying
That could make fireworks with a revolver 
This happened a few times before I figured the charge was too lite.
I’ve used several of their moulds, all aluminum. Never a problem with them.
Best to play is safe 
Thanks for sharing the details.
NOE stands for Night Owl Enterprise best I recall.
That 360-160-WFN is a good looking bullet.
It’s a nice bullet & easy to cast.
My only reservation is that I’d likely run them full throttle a lot, and I’m not sure if my Marlin will need a gas check or not. I just haven’t tested it enough yet.
I’ve shot some plain based bullets at 38 Special level and they didn’t lead, but I didn’t shoot enough to really test accuracy yet.
I have a full power load worked up with the RCBS 38-150-SWC for another gun, that shoots clean. But I don’t have any cast up right now.
My Marlin has ran semi-wadcutters just fine so far, but I’ve not tested that bullet yet, due to being out.