Unspent powder.

[LynnMassGuy]

2 different loads that shoot very accuratlely and feel normal if not a little light are leaving un-burned powder in the brass, in the cylinder, and on the bench in front of me. The first load is 3.3 grains of Herco in .38 special with a 148 grain wadcutter. The other load that is doing it is 4.6 grains if Green Dot in .357 Magnum with a 148 grain wadcutter. They are both being fired from a 4"bbl .357 magnum Security Six. Both loads feel very mild and shoot very well but are making somewhat of a mess. Is this normal.

 

[Sheldon]

My Speer #12 manual does not even show those two powders you used, listed for the 38 Special. I think those slower burning powders are too slow for the 38 Special, which is probably why they don't list loads using them and why they might not be burning cleaner. Unburned powder can cause problems like jamming and such if the unburned powder starts to build up in your pistol. Nothing like a flake of powder under the extractor on a wheelgun to get things stopped fast. I would think faster burning powder might help your problem. I use Bullseye a lot, but my manual also shows Red Dot, 231, HP-38, 700-X, and AA#2 as viable choices in the 38 Special.

 

[Mark whiz]

It's common for slower powders to leave some unburnt powder grains lying around, but as Sheldon said, those may not be the best choices of powders for those calibers anyway.

You might want to try putting a little more crimp on those loads, especially the .357Mag...............................sometimes that will help with the powder "leftovers".

BTW...........I shoot the same pistol and have found that Hodgdon Universal Clays gives me excellent results (158gr LSWCs and 4.0gr for .38 and 7.0gr for .357). And it is a little on the slow end of the burn spectrum and does tend to leave a few unburned grains laying around at the end of the day - but those loads shoot REALLY well for me.

 

[stans]

Those are some really slow powders for your use and you are not generating enough pressure for complete combustion. I would recommend something faster. For wadcutter loads, powders no slower than Unique are usually used and the most popular choices are Bullseye and W-231/HP-38.