Howdy
I have a couple of 1858 Remingtons with 45 Colt conversion cylinders. Mine are the six chamber style, I suspect your Howell conversion for 45 ACP is only five chambers. That is because Howell patented the slightly angled chambers for 45 Colt in the 1858 Remington, because the rims are too large for six chambers in a cylinder the size of the 1858 Remington. Howell sold his patent to Taylors number of years ago, who has exclusive rights to make a six chambered cylinder for the 1858 Remington in large calibers, so he is restricted to only putting five chambers in his large caliber cylinders for the 1858 Remington.
All that aside, if you are going to be using either real Black Powder or Pyrodex in your cartridges you will need to use a Black Powder compatible bullet lube. I used to do all that stuff about putting lube cookies under my bullets in my BP cartridges, and made my own BP lube with Crisco and Beeswax, and pan lubed standard hard cast bullets to get rid of the factory lube and relubed them with my BP lube. Then I discovered the Big Lube series of Black Powder bullets that have a huge lube groove to carry enough BP compatible lube to keep the barrel of a rifle coated with lube for its entire length. I never used lube cookies again.
Here is a photo of one of my BP 44-40 loads on the left and one of my BP 45 Colt loads on the right. Next to each round is the appropriate Big Lube bullet, with and without lube, demonstrating how much lube each bullet carries.
I used to shoot these 45 Colt rounds in my Remingtons all the time.
Because the frame is so thin in the area where the loading ram passes through the frame, and because the grip of a Remington is a little bit more uncomfortable than a Colt SAA, I eventually started shooting 45 Schofield ammunition in my Remmies. The Schofield round being shorter than the Colt round, it holds less powder.
In fact, I designed a Big Lube bullet specifically for the 45 Schofield cartridge. At the time the only Big Lube bullet available for 45 Colt was the 250 grain PRS bullet. I designed a 200 grain bullet which would generate less recoil than the 250 grain bullet, and coupled with the 45 Schofield case, it made a pretty good cartridge for my 45 Colt Remingtons.
The bullet became known as the J/P 45-200, for Johnson and my collaborator whose name was Peterson. Here is a photo of one of my 45 Schofield rounds and the components that go into it. The bullet is the original version of the J/P 45-200.
I would suggest you look into the J/P 45-200 for your Black Powder 45 ACP ammunition. If you don't want to cast them yourself you can buy lubed and sized bullets here:
http://www.whyteleatherworks.com/BigLube.html
I used to cast, lube and size my own bullets, but these days I buy them. The J/P 45-200 is dead center on the page. The shape has undergone some slight changes since when I used to cast them myself, the nose is not quite so flat as mine were.
Here is a photo of all the Black Powder cartridges I load. Left to right they are 44 Russian, 45 Schofield, 38-40, 44-40, and 45 Colt. They all have big lube bullets in them. The 45-70 on the right is the only BP cartridge I load with bullets other than Big Lube bullets.
Here is a photo of the bullets used in these cartridges. All are Big Lube except the 405 grain 45-70 round second from the right, and the standard hard cast 45 Colt round on the far right, illustrating how skimpy the lube grove is in a standard hard cast bullet.
I am not sue if you can use the 45 Cowboy Special in your cylinder, it is a rimmed cartridge, with a rim the same dimensions as the 45 Colt rim. Is your cylinder counterbored for rims? If not, you cannot use the 45 Cowboy Special round. The 45 CS has the same internal capacity as a 45 ACP, and the same Smokeless loading data can be used. The only difference is the 45 Cowboy Special has a rim just like the 45 Colt.
This photo shows several 45 Caliber cartridges. Left to right they are 45 Colt, 45 Schofield, 45 Cowboy Special, 45 Auto Rim, and 45 ACP.
Yes, if you want to load 45 CS you should really use a die that forms a roll crimp. You can use standard 45 ACP dies for decapping, sizing, and belling the case mouth. You can use a 45 Colt die to seat and crimp.
If you don't want to mess with soft BP compatible lube you can load using American Pioneer Powder (APP). It is a BP substitute that does not require BP specific bullet lube, standard bullet lube in standard hard cast bullets works fine with APP.
Regarding a drop tube: I have been loading Black Powder in all of these cartridges for a long time. There is no advantage to using a drop tube for these cartridges. I just pour in enough powder so that when the bullet is seated it will compress the powder between 1/16" -1/8". That's all there is to it, it is really that simple. The only cartridge I use a drop tube for is 45-70.
Regarding Smokeless powder in these cylinders: Understand it is the cylinder, not the frame or barrel that must be able to withstand the pressure generated when a cartridge fires. Not the frame and not the barrel. My cylinders were made of 4150 arsenal grade steel and the caps are made from 4140 steel. I would be surprised if Howell was using a steel inferior to these.
Regarding pressure generated by Cowboy Ammunition: There is no SAAMI standard for Cowboy Ammunition. You will often hear it stated that a velocity of so many feet per second is achieved by certain ammunition. It is too much
pressure, not velocity, that bursts cylinders. Stating velocity means nothing since even with the same weight of bullet the same velocity can be achieved with different powders resulting in widely different pressure.
If I had your 45ACP cylinders I would be loading my ammo with Black Powder and the 45 J/P 200 bullet. No, I do not get any money, I designed the bullet for free, for the Black Powder shooting community, I have never made a penny off of it. If I wanted to load Smokeless I would be using lead bullets with the minimal recommended powder charge from any recognized published loading manual.