From the Dope Bag of the October 1940 American Rifleman - The End of No. 80
"SR (Sporting Rifle) powder No. 80 has been supplanted by SR No. 4759, according to information received from the duPont Burnside Laboratory. It is intended for reduced or midrange charges in rifles and it is not recommended for use in handguns. Per weight of charge it develops higher velocity at lower pressures as compared with No. 80. Also the new No. 4759 powder is cleaner burning and more uniform in ballistical behavior under slightly varying combustion conditions as it is less sensitive to changes in loading density and powder position in the case than was No. 80 powder."

This is my favorite cast bullet powder by far.
Very bulky, takes up a lot of space in the case and will burn cleanly if pressures are elevated just above BP levels.

All my 4759 match loads are ignited with Federal pistol primers. Never had a misfire.

Good info, Frank, thanks.

It moved the bullet a good inch so the engraving was on the first half.   

Powder was somewhat caked together.

Loading density (29gr) was about half full.   

That coupled with the one click-bang points to loading density.

Maybe.  I'll try something different next trip to the range.