For the .41 and .38 's best I can tell they held on to the heel based stuff right through the end of black powder cartridge production. Not so with the .45
Then in their early years of smokeless production they shifted to an internal groove round nose hollow base bullet in .41 and .38 cartridge production hoping the paradigm of getting the bullet to obdurate to fill the bore would work ok in the guns they had already produced without causing penalty in the ones where they had downsized the bore.
History on the problems Colt had and how they addressed them is sometimes contradictory in the sources I have read. But clearly the arrival of the S&W 38 special cartridge caused them great problems in the market and they eventually threw in the towel and adopted the cartridge themselves.
I do believe the straight bore cylinder never worked out for them once smokeless arrived, and exasperated the problem of getting a good gas seal on the use of the .357 diameter bullets, hollow base or not, and especially getting them to enter the forcing cone correctly from those straight bore cylinders in 38 and 41 revolvers.
Colt's .38 and .41 ammo sources went to inside lubrication around the time smokeless came in. They used hollow base bullets to set up in the cylinder and barrel.
There was a gunzine writer who had USFA make him a modernized .41 LC with .386 throats and barrel for solid base inside lubricated bullets.
Code Name: JET STREAM
Using pretty normal current +p data easily gets a 158gr hardcast bullet over 1k fps in a 4" gun.
I have a harder time wrapping my head around why I can't get a 125gr jhp to 1100fps safely with current data.
Tangentially related. I have a Hand Ejector that Mr Jinks said was made between 1916-1919. I'd have to get it lettered for him to nail it down. It has a divot machined into the inside of top strap. When I asked him about it he said that was a space for the trash from the BP loaded .38 Specials to collect so that it wouldn't interfere with the rotation of the cylinder. It was phased out during the 1930s.
Men freely believe that which they desire.
Julius Caesar
Hammer of Thor is more than just stuffing more powder in a cartridge case. Don’t forget that bullet weight makes a significant difference. Nominal bullet diameter is practically the same, but a 158 grain bullet can go places/do things that a lighter weight 115/124 grain bullet can not.