NLM,
First, we are assuming this is for an 1858 NMA Remington model, given the fact that you've posted your question in that section. If so, proceed.
DROP-IN CYLINDERSNext, you need to determine if your gun is an Uberti, Pietta, or 'other' manufacture. If either Pietta or Uberti, proceed. If ASM, ASP, or other manufacturer, send it to a gunsmith for installation and tuning. If Pietta or Uberti manufactured, proceed.
Next, determine date of manufacture by reading either the Roman numerals or capital letters within a box stamped on the lower frame. For dating info, see this thread:
https://coltcountryforum.com/index.php/topic,4942.0.htmlIf your revolver is a Pietta and was manufactured
PRIOR TO 2002 when CAM/CAD machining was introduced, it's quite likely it will
not be a drop-in. I can't say definitively when Uberti moved to this process...proceed with caution.
Next, determine whether you want a SIX SHOT or FIVE SHOT configuration. Note that the six shot version
do not have safety notch between cylinders so when carrying, for safety's sake load five and drop the hammer on the empty. When shooting at the range it's probably OK to load six at the firing line. Both Taylor's and Howell offer the six shot. When installing the six shot version, most likely if it's a drop-in fit, you won't have to mess with timing.
Still with me?
If you have decided the 5 shot is your huckleberry, I recommend sending it to a BP gunsmith. Not only will it need timing (moving from a 6 to 5 shot spacing) but it's recommended a two-stage hand be installed at this time. Also note that altering the timing from a 6 to 5 will make your original C&B cylinder much less likely to operate properly.
If you have determined your gun is a Pietta, post '02 production, and you are going for the Howell's or Taylor's 6 shot conversion, chances are very good it will drop right in with no alterations and swap between conversion and C&B in seconds. However, if it does not...you still have the option to send it to a 'smith. Both Howell's and Taylor's offer installation and fitting services as does our resident gunsmith expert, 45 Dragoon (Goon's Gun Works)
GATED CONVERSION:If planning on a gated conversion, I recommend sending it out. Period.
Links:
Goon's Gun Workshttps://www.goonsgunworks.com/Howell's Old Westhttps://www.howellarms.com/1858-remingtonTaylor's and Co.https://taylorsfirearms.com/accessories/conversion-cylinders/1858-remington.htmlKirst Konverterhttps://kirstkonverter.com/1858-remington.html