We all enjoy our 1917 style 45ACP revolvers, whether it’s a model 25, 325, or 625, for their versatility & big-bore thump. Many of us like them even more when they’re flavored in 45 Colt. Unfortunately it seems S&W doesn’t like stamping 4-letter words on its revolver barrels so they’ve been far & few between, by comparison.
Sadly, just reaming out a 45ACP cylinder to accept the longer 45 Colt cartridge won’t work. Converting a 45ACP (rimless) revolver to shoot 45 Colt (rimmed) is involved, mainly stemming from the gross headspace needed for the moon-clipped rounds as well as the 45ACP’s cylinder’s shorter length & its related extended barrel breach.
The 45ACP is typically loaded with 230gr bullets as a standard max weight though heavier can be found from specialty vendors. Heavier bullets in 45ACP cases just take up too much of the small case’s volume, in my opinion.
The 45 Colt’s ample case length is better suited for 250gr & heavier bullets but at the moderate power level they operate at in the 625 it’s really too much case capacity. Fully charged they often still have too much unused space.
The shorter overall length of the old .45 S&W Schofield would be helpful but it’s still the same problem of trying to adapt a rimmed cartridge to a rimless setup.
.
I got the idea, which is somewhat of a compromise but still the best of both worlds, rimmed & rimless, for use in a 45ACP M625.
Enter the 45 Winchester Short Magnum (45WSM). (That's what I'm calling it for now anyway.
)
You get there by trimming a Starline 45 Winchester Magnum (45WM) rimless case (1.198") down to 45 S&W Schofield length (1.100") & reaming the 45ACP cylinder's chambers to the appropriate depth, to accommodate the 45WSM's extra case length, using a standard 45ACP reamer. That's it.
With them loaded up to 45 Super power level (25K-28K psi) there would be no safety issue since the cylinders can already handle that.
Furthermore, you would not have to worry about a dangerously high power 45WM (41.5K psi, SAAMI) round accidentally finding its way in to one of the modified chambers as they're too long to allow the cylinder to close if it's only reamed to accommodate a 45 Schofield’s length.
As in the 45ACP you can still shoot the taper crimped 45WSM rounds individually (without moon-clips & extracted individually) or with moon-clips.
Use cannelured and heavier 45 Colt bullets with a roll crimp along with moon-clips.
Of course, moon-clipped 45ACP rounds can still be shot in the modified cylinder's chambers, as well as 45 Auto Rims, if desired.
.
.
.
Details on how I did it:
-------------------------
I bought a new stainless M625 45ACP cylinder from MidwayUSA, #666363 (S&W# 412200000) for $118, for the conversion. Of course my original cylinder could have been used as well for the conversion but I wanted to error on the side of caution & use a second cylinder.
Also, as a general rule, I prefer not to shoot short cartridges in chambers intended for longer ones (no 38 Specials in my 357 cylinders, or 40 S&W in my 10mm Auto cylinders), so having a dedicated separate cylinder for this longer cartridge seemed appropriate here.
Modern 625 cylinders are ~1.539” long overall, as this one measured, & it weighs in at 7.3oz as it comes out of the box, only equipped with an extractor.
Four out of six of its throats checked at ~.4528” diameter while the remaining two were tighter on the inside diameter at ~.4522”.
The head end of its chambers ran ~.4790” while the mouth’s end ran ~.4745”.
Their chambers’ shoulder depth averaged .823”.
These measurements are nominal & compare similarly to the other 45ACP cylinders I have.
I have potentially three 45ACP revolvers for the project: 325NG, 325TR & a 625PC. Unfortunately using the heavier weight 625PC (39oz.) was out for this conversion because S&W uses a shorter than normal cylinder (1.425” long) in them.
The other two have standard 1.539” long cylinders so I picked the longer barrel (4” -vs- 2.75”), and slightly heavier weight (31oz –vs- 27oz), 325TR for the conversion. (One day I’ll find a 5” M625 I’ve been wanting.
)
The new cylinder installed in the 325TR revolver easily using the extractor from the 325TR’s original factory cylinder as well as all the other related hardware.
It required no adjustments as the endshake was nominal (like the original’s) and the gross headspace (.097”) & the barrel-cylinder gap (.005”) were also the same as the original’s.
I calculated that a mid-length 45WSM case (1.095”), being .202” longer than a mid-length 45ACP case (.893”), should have the new 45WSM chamber’s shoulder cut to 1.024” deep. (Of the four 45ACP cylinders I have on hand their shoulders averaged .822” deep.)
To be cautious (you can always cut deeper later, if needed, but you can’t add back metal) I decide to go with a shorter shoulder depth of 1.019” initially.
It’s a conservative depth that would also help insure that individual rounds could be fired without moon-clips while headspacing on the chamber shoulder only, as in a semi-auto pistol, which I like to do for casual shooting.
For the job I purchased a standard 45ACP finishing reamer (FA45AUTO), with a solid pilot for Cylinders (not Barrel for semi-autos) from Dave Manson Precision Reamers ($75 + shipping), after confirming with them that it’s cutting depth was adequate for this job.
The reamer’s maximum cutting depth is more than adequate at ~1.160”.
The solid cylinder pilot’s diameter is .4512” & would be fine with my new cylinder’s existing throats. I didn’t see a need to buy the more expensive finisher version with removable pilot & a pilot pack.
The finisher is 5” long, has a 7/16” shank with a 3/8” square drive on the end.
Dave Manson was out of stock at the time I called but they allow back-orders. He said they should have one made & ready to ship in 3-4 weeks max. Mine shipped in just 2 weeks.
Reaming the new cylinder’s chamber depth, by hand in a vise, isn’t difficult but takes some time (at least it did for me). Establishing the new cut is rough for a handful of turns but smooths out & remains so for the rest of the way.
Use adequate cutting oil, moderate pressure, & frequent cleaning of the chamber & reamer to remove the cutting’s chips, will ensure a good finish & longevity of the reamer.
As you near the desired depth, be patient & don’t rush the process. It doesn’t take much to remove more than you expected or wanted. Each chamber took me approximately 25-30 mins.
So how did this part of the process come out?
The new throats are all uniform now, after reaming, at .4529", inside/outside diameter.
The new chamber mouths are unchanged at .4745".
The new chamber heads are now .4810" (+.002" from new), within 45WM SAAMI specs.
Chamber shoulder to cylinder face depth averaged ~1.0145"
Headspace clearance = .014" (shell head to frame, with a 1.094" case headspacing on the chamber's shoulder). This is roughly what was the headspace clearance for a moon-clipped 45ACP round in the factory cylinder.
.
.
Now to conjure up some 45WSM ammo for it.
------------------------------------------------------
COAL:
-------
My COAL” of 1.475” for the 45WSM is based on the 45WM having a SAAMI max COAL of 1.575" & since I removed almost 0.100” from it that seems appropriate.
However, since this will be used in a revolver, & not a pistol, the OAL” of the cylinder will have the final determination of it's ultimate maximum length. I come up with ~1.610” as a maximum COAL, if other factors allow.
Case Capacity:
----------------
A mid-length (1.095”) 45WSM case, cut from a brass Starline 45WM case, will hold 34.3grs of H²O. (Starline’s nickel cases run a tad more at 34.5grs/H²O, for some reason.)
This is 25.6% more volume than a 45ACP case.
In other capacity comparisons, the 45WSM has:
-----------------------------------------------------
1.5% less volume than a 41 MAGNUM
9.7% less volume than a 45 WIN MAG
18.9% less volume than a 45 COLT
7.9% more volume than a 10mm MAGNUM
28.9% more volume than a 357 MAGNUM
42.3% more volume than a 10mm AUTO
Accuracy:
-----------
Using .4512” Hornady 230gr HAP bullets (.648” long) in my work-up loads, so far, it’s been every bit as accurate as before the modification using Unique, Power Pistol & Blue Dot powders loaded to a COAL of 1.435”.
At just under (100) work-up loads thru it, & all fired without moon-clips, I’ve not had any issues.
Some of these used Zero’s 185gr JHP in 45 Super equivalent work-ups also.
I also have (500) .4528” Acme 250gr Hi-Tek coated L-RNFP bullets to work with next. Proportionally these bullets seat more of their .656” length in the case when seated & roll-crimped at the cannelure (.352” deep). COAL is 1.392”
My next L-SWC bullets will have longer noses & seat more of their weight outside of the case.
I’ll be continuing with more range time as I finalize loads.
.
.
What’s in the name:
------------------------
I searched & couldn’t find where this had been done before (apologies if I missed it), and if not, it needed a name.
45 WSM: 45 Winchester Short Magnum seemed the most obvious, since it’s just a shorter version of the 45 Winchester Magnum, also because of the new rifle cartridge trend to name shorter versions “WSM”s.
Some other possibilities:
45 SLA: 45 Super Long Auto, being essentially a longer version of the 45 Super.
45 SCA: 45 Short Colt Auto, being essentially a shorter rimless version of the 45 (Long) Colt but for use in a semi-auto.
45 SWA: 45 Smith & Wesson Auto, seeing S&W doesn’t have a .45 semi-auto cartridge with its name on it.
Maybe they should?
.
.
.
.
Sadly, just reaming out a 45ACP cylinder to accept the longer 45 Colt cartridge won’t work. Converting a 45ACP (rimless) revolver to shoot 45 Colt (rimmed) is involved, mainly stemming from the gross headspace needed for the moon-clipped rounds as well as the 45ACP’s cylinder’s shorter length & its related extended barrel breach.
The 45ACP is typically loaded with 230gr bullets as a standard max weight though heavier can be found from specialty vendors. Heavier bullets in 45ACP cases just take up too much of the small case’s volume, in my opinion.
The 45 Colt’s ample case length is better suited for 250gr & heavier bullets but at the moderate power level they operate at in the 625 it’s really too much case capacity. Fully charged they often still have too much unused space.
The shorter overall length of the old .45 S&W Schofield would be helpful but it’s still the same problem of trying to adapt a rimmed cartridge to a rimless setup.
.
I got the idea, which is somewhat of a compromise but still the best of both worlds, rimmed & rimless, for use in a 45ACP M625.
Enter the 45 Winchester Short Magnum (45WSM). (That's what I'm calling it for now anyway.
)You get there by trimming a Starline 45 Winchester Magnum (45WM) rimless case (1.198") down to 45 S&W Schofield length (1.100") & reaming the 45ACP cylinder's chambers to the appropriate depth, to accommodate the 45WSM's extra case length, using a standard 45ACP reamer. That's it.
With them loaded up to 45 Super power level (25K-28K psi) there would be no safety issue since the cylinders can already handle that.
Furthermore, you would not have to worry about a dangerously high power 45WM (41.5K psi, SAAMI) round accidentally finding its way in to one of the modified chambers as they're too long to allow the cylinder to close if it's only reamed to accommodate a 45 Schofield’s length.
As in the 45ACP you can still shoot the taper crimped 45WSM rounds individually (without moon-clips & extracted individually) or with moon-clips.
Use cannelured and heavier 45 Colt bullets with a roll crimp along with moon-clips.
Of course, moon-clipped 45ACP rounds can still be shot in the modified cylinder's chambers, as well as 45 Auto Rims, if desired.
.
.
.
Details on how I did it:
-------------------------
I bought a new stainless M625 45ACP cylinder from MidwayUSA, #666363 (S&W# 412200000) for $118, for the conversion. Of course my original cylinder could have been used as well for the conversion but I wanted to error on the side of caution & use a second cylinder.
Also, as a general rule, I prefer not to shoot short cartridges in chambers intended for longer ones (no 38 Specials in my 357 cylinders, or 40 S&W in my 10mm Auto cylinders), so having a dedicated separate cylinder for this longer cartridge seemed appropriate here.
Modern 625 cylinders are ~1.539” long overall, as this one measured, & it weighs in at 7.3oz as it comes out of the box, only equipped with an extractor.
Four out of six of its throats checked at ~.4528” diameter while the remaining two were tighter on the inside diameter at ~.4522”.
The head end of its chambers ran ~.4790” while the mouth’s end ran ~.4745”.
Their chambers’ shoulder depth averaged .823”.
These measurements are nominal & compare similarly to the other 45ACP cylinders I have.
I have potentially three 45ACP revolvers for the project: 325NG, 325TR & a 625PC. Unfortunately using the heavier weight 625PC (39oz.) was out for this conversion because S&W uses a shorter than normal cylinder (1.425” long) in them.
The other two have standard 1.539” long cylinders so I picked the longer barrel (4” -vs- 2.75”), and slightly heavier weight (31oz –vs- 27oz), 325TR for the conversion. (One day I’ll find a 5” M625 I’ve been wanting.
)The new cylinder installed in the 325TR revolver easily using the extractor from the 325TR’s original factory cylinder as well as all the other related hardware.
It required no adjustments as the endshake was nominal (like the original’s) and the gross headspace (.097”) & the barrel-cylinder gap (.005”) were also the same as the original’s.
I calculated that a mid-length 45WSM case (1.095”), being .202” longer than a mid-length 45ACP case (.893”), should have the new 45WSM chamber’s shoulder cut to 1.024” deep. (Of the four 45ACP cylinders I have on hand their shoulders averaged .822” deep.)
To be cautious (you can always cut deeper later, if needed, but you can’t add back metal) I decide to go with a shorter shoulder depth of 1.019” initially.
It’s a conservative depth that would also help insure that individual rounds could be fired without moon-clips while headspacing on the chamber shoulder only, as in a semi-auto pistol, which I like to do for casual shooting.
For the job I purchased a standard 45ACP finishing reamer (FA45AUTO), with a solid pilot for Cylinders (not Barrel for semi-autos) from Dave Manson Precision Reamers ($75 + shipping), after confirming with them that it’s cutting depth was adequate for this job.
The reamer’s maximum cutting depth is more than adequate at ~1.160”.
The solid cylinder pilot’s diameter is .4512” & would be fine with my new cylinder’s existing throats. I didn’t see a need to buy the more expensive finisher version with removable pilot & a pilot pack.
The finisher is 5” long, has a 7/16” shank with a 3/8” square drive on the end.
Dave Manson was out of stock at the time I called but they allow back-orders. He said they should have one made & ready to ship in 3-4 weeks max. Mine shipped in just 2 weeks.
Reaming the new cylinder’s chamber depth, by hand in a vise, isn’t difficult but takes some time (at least it did for me). Establishing the new cut is rough for a handful of turns but smooths out & remains so for the rest of the way.
Use adequate cutting oil, moderate pressure, & frequent cleaning of the chamber & reamer to remove the cutting’s chips, will ensure a good finish & longevity of the reamer.
As you near the desired depth, be patient & don’t rush the process. It doesn’t take much to remove more than you expected or wanted. Each chamber took me approximately 25-30 mins.
So how did this part of the process come out?
The new throats are all uniform now, after reaming, at .4529", inside/outside diameter.
The new chamber mouths are unchanged at .4745".
The new chamber heads are now .4810" (+.002" from new), within 45WM SAAMI specs.
Chamber shoulder to cylinder face depth averaged ~1.0145"
Headspace clearance = .014" (shell head to frame, with a 1.094" case headspacing on the chamber's shoulder). This is roughly what was the headspace clearance for a moon-clipped 45ACP round in the factory cylinder.
.
.
Now to conjure up some 45WSM ammo for it.
------------------------------------------------------
COAL:
-------
My COAL” of 1.475” for the 45WSM is based on the 45WM having a SAAMI max COAL of 1.575" & since I removed almost 0.100” from it that seems appropriate.
However, since this will be used in a revolver, & not a pistol, the OAL” of the cylinder will have the final determination of it's ultimate maximum length. I come up with ~1.610” as a maximum COAL, if other factors allow.
Case Capacity:
----------------
A mid-length (1.095”) 45WSM case, cut from a brass Starline 45WM case, will hold 34.3grs of H²O. (Starline’s nickel cases run a tad more at 34.5grs/H²O, for some reason.)
This is 25.6% more volume than a 45ACP case.
In other capacity comparisons, the 45WSM has:
-----------------------------------------------------
1.5% less volume than a 41 MAGNUM
9.7% less volume than a 45 WIN MAG
18.9% less volume than a 45 COLT
7.9% more volume than a 10mm MAGNUM
28.9% more volume than a 357 MAGNUM
42.3% more volume than a 10mm AUTO
Accuracy:
-----------
Using .4512” Hornady 230gr HAP bullets (.648” long) in my work-up loads, so far, it’s been every bit as accurate as before the modification using Unique, Power Pistol & Blue Dot powders loaded to a COAL of 1.435”.
At just under (100) work-up loads thru it, & all fired without moon-clips, I’ve not had any issues.
Some of these used Zero’s 185gr JHP in 45 Super equivalent work-ups also.
I also have (500) .4528” Acme 250gr Hi-Tek coated L-RNFP bullets to work with next. Proportionally these bullets seat more of their .656” length in the case when seated & roll-crimped at the cannelure (.352” deep). COAL is 1.392”
My next L-SWC bullets will have longer noses & seat more of their weight outside of the case.
I’ll be continuing with more range time as I finalize loads.
.
.
What’s in the name:
------------------------
I searched & couldn’t find where this had been done before (apologies if I missed it), and if not, it needed a name.
45 WSM: 45 Winchester Short Magnum seemed the most obvious, since it’s just a shorter version of the 45 Winchester Magnum, also because of the new rifle cartridge trend to name shorter versions “WSM”s.
Some other possibilities:
45 SLA: 45 Super Long Auto, being essentially a longer version of the 45 Super.
45 SCA: 45 Short Colt Auto, being essentially a shorter rimless version of the 45 (Long) Colt but for use in a semi-auto.
45 SWA: 45 Smith & Wesson Auto, seeing S&W doesn’t have a .45 semi-auto cartridge with its name on it.
Maybe they should?
.
.
.
.
Last edited:
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