Reflections on Centaure Conversions & the 1871-72  Open Top

# The Gold Standard - How Do Measurements of Modern 1860 Cap & Ballers or their Conversions Compare to Originals?

# Working Assumptions

# 1860 Armies

# Thuer Armies

# Richards Armies

# Richards-Mason Armies

# Caveat Regarding Modern Colt Breech Loading Army Conversions

# Conclusions

# Yes we can but do we Want?


The Gold Standard - How do Measurements of Modern 1860 Cap & Ballers or their Conversions Compare to Originals? This is the time to ask which repros are close to the measurements, to that gold standard set by the original Colt Armies from yesteryear.

Are our measurements of the 1st generation and period conversions within the ranges provided by R. Bruce McDowell in his sought after “conversion bible” from 1997 titled A STUDY OF COLT CONVERSIONS AND OTHER PERCUSSION REVOLVERS?

What is the impact of production tolerances back then and today?

To answer these questions for

# Colt 1860 Army Pattern C&B Pistols – Sample (reference 1st gen Colt 1860 Army)

·        Centaure 1960 Civilian & RNMAs of production 1960 through 1972

·        2nd & 3rd gen Colt 1860 Army

·        Euroarms

·        Pietta

·        Uberti

# Colt 1860 Army Pattern Conversion Pistols – Sample (reference 1st gen Colt 1860 Army Thuer, Richards, Richards-Mason conversions)

·        Dave Anderson USPFA Richards

·        Gren 2nd gen Colt Richards

·        Kenny Howell 2nd gen Colt Richards

·        Karl Nedbal Centaure Thuer, Richards, Richards-Mason

·        Karl Nedbal Uberti Thuer

·        R&D 2nd gen Colt Richards

·        Uberti Richards Transitional, Richards-Mason

in a reasonable way measurements were taken in a standardized manner with digital calipers. This task could be accomplished within a short period of time thanks to the help of the FROCS community around the globe. These are the critical areas measured and eventually compared:

# front diameter of the cylinder

# rebate diameter of the cylinder

# overall height of the barrel lug

Working assumptions: A healthy human eye will note differences of ca. 0,5 mm/.02 in in size of comparable objects.

·     Deviations within these ranges are considered “regular production tolerances” (RPTs), or not significant.

·    Deviations beyond RPTs are considered significant. They are what we refer to as “beefed-up” or “on steroids”. Hence, they are printed in bold face type in the tables below.

The numbers in brackets in the Serial Number column indicate the number of pistols per manufacturer measured. Numbers in that same column without brackets are serial numbers of individual guns.

When more than 1 gun was available from a manufacturer measurements were averaged, to take into account production tolerances. Ranges of the measurements are provided as appropriate.

Measurements of 1st gen. Colt Army pistols are printed in blue/red bold type.

Blue * marked data is from McDowell’s book.

Facts & Figures (mm/in)

Model Army 1860

Serial Number

Cylinder Diameter


Cylinder Diameter Rebate

Barrel Lug


Centaure 1960 NMA

average (9)






40,67/1.601 - 41,00/1.614

38,23/1.505 - 38,90/1.531

47,43/1.867 - 47,83/1.883

Colt 1860 Army 1st gen

average (3)






41,15/1.621 - 41,23/1.623

38,75/1.526 - 38,96/1.534

47,42/1.867 - 47,92/1.887

Colt 1860 Army 1st gen




n. a.

Colt 1860 Army 2nd gen

average (12)






40,71/1.602 - 40,88/1.610

38,76/1.526 - 39,15/1.541

46,46/1.829 - 47,54/1.872

Colt 1860 Army 3rd gen





Euroarms 1860 Army





Pietta 1860 Army

average (3)






40,44/1.592 - 40,51/1.595

38,79/1.527 - 38,99/1.535

47,04/1.852 - 47,63/1.875

Uberti 1860 Army

average (4)






40,49/1.594 - 41,91/1.650

38,86/1.530 - 39,67/1.562

46,99/1.850 - 47,72/1.879

This 1860 Army data above indicates that most measurements from modern C&B 1860 model revolvers are within RPTs if we accept that only three (3) 1st gen originals were at hand for reference. If that is OK one should also note the very close tolerances of these 1st generation Colts!

Please, note some selective comments regarding brands or manufacturers below.

FAUL’s Centaure

Colt Army 2nd generation

# Centaures front & rebate diameters are below RPTs

# 2nd gen. Colts barrel lug height ranges are below RPTs

Colt Army 3rd generation

Euroarms 1860 Army

# 3rd gen. Colt barrel lug height is below RPTs

# Euroarms barrel lug height is above RPTs

Pietta 1860 Army

Uberti 1860 Army

# Pietta front cylinder diameters are below RPTs

# Uberti front cylinder and barrel lug height ranges are below, the rebate cylinder diameter ranges above RPTs.


Thuer Army Conversions: Only a small sample of four (4) Thuers was available for measurements, two (2) original Colts from the 19th century and two (2) Nedbal conversions (table below). Therefore, only a few careful comments seem appropriate:

# The height of the barrel lug of the two (2) original Colts is smaller than that of their C&B versions presented in the table above, and only just within their respective RPTs.

# The measurements of the two (2) Nedbal conversions are almost identical although base guns of different makers were converted. This was expected regarding their cylinders because they were copied from the same original in his collection. Some additional details:

Facts & Figures (mm/in)

Model Thuer Army

Serial Number

Cylinder Diameter


Cylinder Diameter


Barrel Lug


Colt 1860 Army Thuer

average (2)




Nedbal Centaure 1960 Thuer





Nedbal Uberti 1860 Thuer





# Colts’ rebate cylinder diameter is above RPTs compared to the respective C&B originals. This might indicate that it was purpose made back then but was not a converted percussion cylinder.

# The height of barrel lug of the two Nedbal conversions is above RPTs of Colt Thuers but within reference C&B originals!

Nedbal Uberti Thuer Army from the right side

Nedbal Uberti Thuer Army left side

Pictures of rare custom and replica industry Thuer Armies below.

HEGE Thuer Army made of Uberti parts

Uberti factory Thuer


Richards (RI) Armies: We are comforted that the specs of the four (4) originals from the 1870s are within RPTs, like those of their C&B brothers. The Anderson, Centaure and Howell 2nd gen. Colt conversions are within RPTs, whereas the Gren and R&D 2nd gen. Colts are off in one measurement only, but the Uberti Richards Transitional (RII: they don’t make a RI) is pretty much beefed-up!

Details regarding these significant deviations from the RPTs are listed below.

Facts & Figures (mm/in)

Model Richards

Serial Number

Cylinder Diameter Front

Cylinder Diameter Rebate

Barrel Lug


Anderson USPFA 1860 Richards





Colt 1860 Army Richards




n. a.

Colt 1860 Army Richards

average (4)









Gren Colt 2nd gen Richards

average (2)









Howell Colt 2nd gen Richards

1996 (p)




Nedbal Centaure 1960 Richards





R&D Colt 2nd gen "Richards"

1979 (p)




Uberti 1860 Richards II





Here are a few more specific comments regarding the above measurements and pictures of rare and not so rare modern Richards (RI and RII) custom and factory conversions.

USPFA Richards (RI)

Gren 2nd gen Colts Richards (RI)

# USPFA Richards is within ranges of originals

# Gren 2nd gen Colt rebate cylinder diameters are below RPTs

Nedbal Uberti Richards (RI)

Uberti factory Richards Transitional (RII)

# R&D 2nd gen Colt front cylinder diameter is below RPTs

# beefed-up Uberti RII in all 3 measurements!

Nedbal Centaure Richards (RI) #4079 (top) & Richards Transitional (RII) #6981 (bottom)


Richards-Mason Army: We only have the McDowell data for reference. Regretfully, he is offering no measurements for barrel lug height. Although Colt used newly fabricated barrels for their RMs, the geometry of the frames was not altered. Therefore, it is fair to assume that the height of the Colt RM barrel lug compares to their C&B brothers.

No data of original RMs could be provided by any of the FROCS members around the globe.

Facts & Figures (mm/in)

Model Richards-Mason



Cylinder Diameter Front

Cylinder Diameter Rebate

Barrel Lug


Colt 1860 Army RM




n. a.

Nedbal Centaure 1960 RM





Uberti 1860 RM





Here are the findings:

# The forward area of both Centaure & Uberti RM cylinders are beefed-up

# the Centaure is OK in the other 2 measurements but the Uberti is beefed up in all 3 departments!

Go figure.

Nedbal Centaure RM (top) Uberti factory RM (bottom)


Caveat Regarding Modern Colt Breech Loading Army Conversions: According to the research of the late R. Bruce McDowell there are a few other important findings. You may want to consider them when looking for a modern, dimensional and technically correct conversion.

“Richards Transitional”: ~ 4-screw frame, fluted cylinder

“Richards conversion”: ~ 4-screw frame, barrel contour

# Armies with 8” barrels, 3-screw frames and rebated cylinders only were subject to factory conversions.

# No factory converted short barrelled, or 4-screw frame or fluted cylinder Armies are known to exist.


Conclusions: So, where is all this measuring and comparing getting us? These are my subjective conclusions (you were warned about my subjectivity):

# According to our sample the majority of 1st generation Colt 1860 Armies was built with close production tolerances.

# Contrary to opinions voiced elsewhere this applies to their modern clones and re-issues as well.

# If the objective of your conversion project is historical or dimensional correctness rather, of a safe, reliable shooting iron the quality of the steel used for both the base gun & newly manufactured conversion barrel/liner & cylinder becomes THE key issue.

# Centaures are made of harder steel than Italian C&B pistols.

# Historically and dimensionally correct conversion pistols are not available off the rack, only custom made!

# To me this page helps to rationalize my prejudices and preferences vis-à-vis the best wifey of them all to get financial funds sanctioned for my Centaure conversions!

4 x modern 1860 Model Army pistols (top down): Nedbal Centaure Richards #4079, Uberti Richards-Mason #X02711, 2nd gen Colt Army #US0858, Uberti Richards Transitional #X04444


“Yes we can – but do we want?: Some collectors and cowboy gun shooters consider the Colt M 1871-1872 Open Top the queen of the Colt conversions. With the experience already gathered from other Centaure conversion projects it appears the way is now paved for the making of a Centaure Open Top with Army grips in .44 Colt cal. using many original Belgian Centaure parts. Here is the shopping list and a rough outline of such a project:

#1.: original Centaure back-strap, grip and frame incl. small parts can be used. Centaure 3-screw frame needs to have steel plate welded to the lower forward portion to get one straight platform without the typical Army C&B pistol step, see picture below of original OT. A loading gate must be added. Hammer needs to be reworked and a firing pin added, similar to RM project.

#2.: Uberti steel trigger-guard needs to be mated to Belgian frame, back-strap and grip.

Nickel plated original Colt Open Top with ivory grips of Army size: chambered for the .44 Henry rim fire cartridge

#3.: new cartridge cylinder with gas ring needs to be lathed from ordnance steel and engraved in the pattern of the other Centaure conversions. No big deal for a conversion artist.

#4.: semi-finished 7,5” Uberti OT barrel with integrated rear sight in .44 cal./.429 dia needs to be procured, re-contoured and fitted, see RM project, ditto an Uberti OT type wedge.

#5.: new OT ejector housing needs to be made and mated to barrel, see RM project.

Such a Centaure Open Top will have even more Italian genes than the previous Centaure Richards-Mason conversion project.

Will I pursue such a project the War Department permitting?

Probably not. Let me explain:

# Technically and compared to e. g. a Thuer or Richards the making of an Open Top from a Centaure C&B pistol is an unsophisticated piece of solid gunsmith work, but it might represent some unexpected challenges nonetheless.

# Therefore, an experienced, dedicated and top notch conversion artist is required to professionally execute such a project . In Europe I only would trust Karl Nedbal with this task. But Karl will no longer be available for such challenges because he retired during the month of April 2011 …


Finally given the options available to own a modern, hard steel and quality made 1860 model conversion revolver with measurements of a Civil War period Colt M 1860 Army and with due respect to my friends in Gardone and Meßkirch I will be choosing the Centaure customs conversion in .44 Colt caliber every day of the week.

Nedbal Centaure Army Conversions proudly displayed on top of the Austrian flag (top to bottom): Thuer #7266, Richards #4079, Richards Transitional #6981, Richards-Mason #6176, “Mystery” #11691

With that said I am bowing my head in great respect to the outstanding work of Austrian master Karl Nedbal, as exemplified by above quintet of Centaure Army conversions he did for me.

Thanks, my friend, you have been doing good!


WDN/April 3, 2013

© 2007 Wolf D. Niederastroth