Howdy
I have two 1858 Remingtons with the original six shot 45 Colt R&D cylinders that Taylors sells.
Ken Howell took out a patent on his six shot cylinder for the 1858 Remington because six 45 Colt rims would not fit in a cylinder that size without interfering with each other. So Howell bored the chambers at a slight angle, less than 1/2 of one degree, so there would be room for six 45 Colt rims without interfering with each other. No, the slight angle does not make any difference in accuracy, these Remingtons are the most accurate 45 Colt revolvers I own, more accurate than my Colts, clones, or Rugers.
For some reason, Ken sold his patent rights to Taylors. Taylors now has somebody else making their cylinders. Because he sold his patent, Howell cannot make a cylinder with angled chambers. So the only six shot cylinder he offers for the 1858 Remington is chambered for 44 Colt, not 45 Colt. Do not make the mistake of buying that one.
Personally, I never saw the need to put a gate on my Remmies. It is so simple to pop the cylinder out for loading and unloading, that I never saw the need for a loading gate. Plus, you need an ejector to pop out the rounds if you have a loading gate.
On top of that, using the six shot cylinder without a loading gate, I can pop the original C&B cylinder back in if I want to shoot my Remmies as Cap & Ball.
Yes, the cylinders are expensive. My excuse is that I bought my Remmie so long ago (1975) that it had long ago amortized its expense, so buying the cylinder was like buying a new cartridge gun for just the price of the cylinder.
Not long after I converted my first Remmie, I lucked into a used Uberti Stainless Remington that came with the R&D cylinder for a great price.