3F will produce a higher pressure then 2F but that is no guarantee that it will produce a higher velocity for the bullet because of the problem that can happen in my last post. In other words a whole column of 2F ignited by the cap all at once can give the same or even more velocity then 3F if it's same length of column does not all ignite by the cap at once.
In revolvers the cap blast most likely can make through 3F ok But it might not in a rifle where the powder column is 3 times longer.
Plus the fact that since the 3F burns faster and creates a higher pressure, that any powder not getting lit by the cap will packed so dense that it can get thrown out the muzzle without burning.
This is all explained in this document below: (plus anything else you would ever want to know about gunpowder) If I remember right it was printed in 1886.
HANDBOOK OF THE MANUFACTURE AND PROOF OF GUNPOWDER,
AS CARRIED ON AT THE Royal Gunpowder Factory, Waltham Abbey.
Captain F. M. SMITH, Royal Artillery,
ASSISTANT SUPERINTENDENT.
Printed By Order Of The Secretary Of State For War.
LONDON:
Printed under the Superintendence of Her Majesty's Stationery Office
By George Edward Eyre and William Spottiswoode,
Printers to the Queen's most Excellent Majesty.
And sold by W. Clowes & Sons, 14, Charing Cross; Harrison & Sons, 59, Pall Mall;
W. H. Allen & Co., 13, Waterloo Place; W. Mitchell, 39, Charing Cross;
Longman & Co., Paternoster Row; and Trubner & Co., Paternoster Row;
Also by A. & C. Black, Edinburgh;
Alex. Thom, Abbey Street, and E. Ponsonby, Grafton Street, Dublin;
Price Five Shillings.