Welcome to the forum.
The site above is a good one but several years out of date now. Below is my complete list excluding Bisley and Birdshead which are all steel and all the same size regardless of usage:
All GRIP FRAME MATERIAL & IDENTIFICATION NUMBERS (Founder's Marks) CAST ON GRIP FRAMES (N/A to Bearcat)
Notes:
Most all grip frames are 1/2" thick unless otherwise noted below.
For convenience, NM frames in the two most common sizes are often referred to by their old model #s as XR3 'SIZE' or XR3-RED 'SIZE' but they have their own Casting numbers.
NM BLUE STEEL and ALLOY:
Small steel (OM #XR3 size) 1/8" closer to trigger guard than XR3-RED size, (cut for indexing pawl system, no extensions into main frame & only 7/16" thick) = A (in a square), no other marking observed; w & w/o lock. New Vaq w/o lock has a 512 prefix serial #, locks discontinued in 2012
Large steel (OM #XR3-RED size): Early = A (in a square) XR-3 (that's XR dash 3), Late = A & T in separate 1/8" circles
Large alloy (OM #XR3-RED size) w/o lock: Early = NXR3-RED, Late = XRN-3RED. With lock = XR & L, locks discontinued in 2012
Short steel 'Vaquerito' .32s = A (in a square) XR-3. If ordered as a separate part = 302 A (in a square) 3/16" shorter in length than the XR3 and XR3-RED sizes
SBH = No marking on Dragoon frames (1/4" longer than standard grip). Large round guard steel frames supplied on all barrel lengths less than 7 ½" (Old Model #XR3-RED size) = same as Large steel above marking
Birdshead** steel = # in circle, MR00307, A in circle
Bisley** steel grip frames come in only one size that fit all Ruger new models.
NM STAINLESS:
Small, (XR3 size) 1/8" shorter horizontally behind the trigger guard (cut for indexing pawl system, no extensions into main frame & only 7/16" thick = K (in circle); w & w/o lock
Large (OM #XR3-RED size): Earliest = KXR-3*, Next = KXR-3 with a separate N, Late = K (in circle) XRN-3, most current = no markings
Short 'Vaquerito' .32s = KXR-3* 3/16" shorter in length than the XR3 and XR3-RED sizes
SBH Hunter = KHRN 3 (Dragoon length but with a round trigger guard)
SBH = No marking on Dragoon frames (1/4" longer than standard grip). Large round guard steel frames supplied on all barrel lengths less than 7 ½" (Old Model #XR3-RED size) = same as Large above marking
Birdshead** = # K in circle, MR00307
Bisley** steel grip frames come in only one size that fit all Ruger new models.
OM BLUE STEEL and ALLOY:
Small alloy = XR3, original style to 1962, 1/8" closer to trigger guard than large size
Large alloy = XR3-RED, (part # SS3), new style in 1962 to 1972, also used on Pre 1985 Old Army - alloy w/narrow trig slot, and on Hawkeye - alloy w/wide trigger slot
SBH = steel dragoon, sq back trigger guard (1/4" longer than standard grip) no marking; Early 'long frame' 5/32" longer than later dragoon marked with C (only ~300 made)
Old Army steel (OM XR3-RED size) = XRN-3 beginning 1985 with wide trigger slot and is the only OM GF in carbon steel other than the SBH.
STAINLESS OM - Old Army only:
Large (OM XR3-RED size) = KXR-3*
*Note: same # KXR-3 used on two different frames: earliest NM SS XR3-RED size and OM SS Old Army XR3-RED size, because based on how they are machined, they can be used for either application.
**Birdsheads and Bisleys supplied on New Vaqueros cut for free spin pawl system and have no extensions into main frame, but are interchangeable to all models.
BRASS FRAMES OM only:
Marked "MR-3DB." = Super Blackhawk Brass "Dragoon" style with square back trigger guard. Same dimensions as 1959 Super Blackhawk. Initially for Super Blackhawks only, then shipped on various Blackhawks, majority in 1972.
The three basic grip frame sizes: Just be aware that the New Model Flat Top BH & NEW Vaquero XR3 size steel grip frames are 7/16" thick, old model XR3 size and all other steel and aluminum frames are 1/2" but this does not affect the interchangeability, just the feel in your hand.
BISLEY VS. DRAGOON GRIP FRAMES:
In Cary's sketch below, unfortunately the front edge of the two grips are not aligned for easy comparison. The SBH plow handle grips are effectively a slight 1/8" shorter on the fore grip. Both the SBH and standard XR3-RED grip frame are both wider than the Bisley at that section of the grip frame level with the trigger guard, and at the butt. The Bisley is longer on the backstrap which goes up higher and I think why some prefer it. I don't like the dragoon sq trigger guard so I've opt for the SBH Hunter with round guard on all my big bore single action Rugers.
I measured the Bisley and the Flat Top XR3 grip frames from the vertical center of trigger when cocked, horizontally to the back strap; 2.790" vs. 2.830" respectively.
So the Bisley is .040" (>3/64") shorter than the Flat Top grip frame; within margin of error due to grip frame finishing variances.
Bisley is .210" shorter than the XR3-RED grip frame 3.000".
Bisley is .250" shorter than SBH Dragoon grip frame 3.040".
But the Bisley grip measures .177" (almost 3/16") closer to the trigger guard than the standard XR3-RED size (aluminum and steel) and almost ¼" closer than the Dragoon grip. Because the Bisley trigger guard is larger, therefore closer to the grip frame, it gives the Bisley the absolute least space of any Ruger grip frame. Even closer than the old 'knuckle busting' XR3 size plow handle grip frame!
So the SBH/Hunter Dragoon grip frames have the most of any Ruger grip frames, and the round guard Hunter has the least chance of rapping the knuckle under recoil.
COMPLETE USAGE OF BLUE STEEL GRIP FRAME VS. ALUMINUM ALLOY INCLUDING SIZE, and USAGE OF STEEL VS. ALUM EJECTOR ROD HOUSING:
Note: Ruger refers to their blue steel grip frames as alloy steel in their catalog, meaning Chrome Molybdenum (Chromoly) as opposed to Alum alloy, and the stainless steel grip frames.
Blue steel GFs* on the following models:
All New Model Flat Top Blackhawk mid and large size cylinder frames.
All New Vaquero mid & large size cylinder frames, XR3 size (also cut for indexing pawl system, no extensions into main frame & only 7/16" thick).
All original large frame Vaqueros, XR3-RED size.
All Super BHs old and new models, XR3-RED size on short brl. lengths; Dragoon size with 7 1/2" & 10" barrels.
All .32 Mag Vaq. style single sixes, SHORT grip & XR3-RED size.
Old Army beginning 1985, XR3-RED size.
All Bisley and Birdshead grip frames.
All "Super" Bearcat old models introduced in 1971, have steel frames.
All new model Bearcats introduced in 1993, have steel frames.
Aluminum alloy grip frames on the following models:
All blue Super Single SAixes 22 and 32, XRE-RED size.
All large size cyl frame NON-flat top Blackhawks, XR3-RED size.
All Old Models, XR3 size, pre 1963.
All Old Models 1963 to 1973, XR3-RED size, including Hawkeye single shot.
Old Army XR3-RED size, pre 1985.
All Old Model Bearcats prior to the Supers have alum alloy frames.
Steel ERH* on the following models:
All pre c. 1962 old models including Bearcats; new model Super BHs since c. 1999 in all barrel lengths (including 5" ERH on 44 & 357 Max 10" barrel).
Original Vaquero large frames post c. 1999.
All New Vaqueros and .32 single six 'Vaqueritos'.
All New Model Flat Top Blackhawks.
Alloy ERH* on the following models:
All old models with alloy grip frames post 1962.
Old Model and NM Super BHs post c. 1962 and pre c. 1999.
Original large frame Vaqueros pre c. 1999.
Old model Bearcats post 1962.
All "Super" Bearcat old models introduced in 1971.
All new model Bearcats introduced in 1993.
The early stainless new model Bearcats have alloy silver anodized ERHs, only recently changed to Stainless ERHs.
*NOTE: There are several dealer exclusive, non-regular production model exceptions to the above such as the Buckeye Blackhawk convertibles that have steel GFs and ERHs, etc.
