.32 Colt Conv. to .380


November 24, 2006, 08:59 PM
Was looking thru GUNSAMERICA and noticed the following in an add for a .32 Colt 1903 model. It was under Ft. Bend Armory and GA#: 976469202. In part it read, " I rewarded it by up grading it to a 380. Simply bought a 380 barrel and magazine, Wala." Is this Possible? If so, where do you get a barrel and magazine and wouldn't you need at least a new recoil spring also?
Someone with more knowledge about Colt's educate me.

If you enjoyed reading about ".32 Colt Conv. to .380" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!
November 24, 2006, 09:01 PM
Didn't know this was possible. You'd think the Slide would have to be milled to accept a larger diameter barrel?..

November 25, 2006, 03:09 AM
I've been told by a few people on the web that it is possible but I think it was a few different parts.

I've got a 1903 that was my grandfathers carry gun. I really like the feel of the gun. I've thought about trying the .380 mod but am going tojust leave it alone

Mac Attack
December 8, 2006, 10:28 PM
For what its worth, I was researching the same thing on the Nurmrich Colt forum but I wanted to know if you could go from .380 ACP to .32 ACP. I found that the frame and slide on a 1903 .32 ACP is the same as that of a 1908 .380 ACP. The Nurmrich site (e-parts site) states they have a few .32 barrels and some .380 barrels for 1/8 and 3/32 inch extractor cuts.

My .380 barrel is pitted so I plan to pick one up as well as a .32 just for fun.


Jim K
December 8, 2006, 10:46 PM
Not to rain on parades, but the main problem is that the .380 magazine won't fit in the .32 frame, and the .380 cartridge won't fit in the .32 magazine. So the magazine well of the .32 has to be made larger to take the .380 magazine. Also, the recoil spring of the .380 is stronger and has more coils.


Old Fuff
December 9, 2006, 12:21 AM
There can also be a problem with the ejector, which includes cartridge guides. While the same part was used in both .32 and .380 pistols, they were individually modified by the final assemblers for each respective gun. Colt depended largely on their skilled work force. In March 1945, a government inspection team looking into problems with the .380 pistol ask Colt for a set of drawings for the 1908 pocket pistol, caliber .380 - and were informed that such drawings were not available. :eek:

These pistols were largely had fitted, and mix & matching parts can bring one to grief. :uhoh:

December 9, 2006, 11:24 AM
I thought this all sounded too good to be true. Glad Old Fuff and Jim Keenan chimed in 'cause I was about to order some parts. Guess I'll just have to find a .380 somewhere (that's what I really wanted to do all along).

Old Fuff
December 9, 2006, 11:57 AM
In all fairness I am aware of some .32 to .380 conversions that have worked, but like Jim I'm aware of some that didn't.

During the time that the model M was made Colt, was able to do an extraordinary amount of handwork on each pistol. Since the "M" designation covered both caliber pistols I suspect that the raw frames and slides might have been the same, but that those intended to be made into .380 pistols were altered by someone, or the final assembler using a file(s). This could account for the reason that some .380 pistols (at least those sold to the armed forces during late World War Two) had some feeding and other problems that didn't show up in the 1903 .32 pistols.

I had a friend that was an officer in the British SAS who had, shall we say, "extensive experience in handgun combat." He was a solid fan of the .32, which he called, "The most reliable pistol of its kind," but never said anything in like terms about the .380 pocket model.

From a user's point of view, the big problem today in either caliber is to find decent, but reasonably priced, magazines. As is the case with all pistols, good magazines are critical for reliability.

December 9, 2006, 12:44 PM
Excuse my ignorance about the 1903. But would the increased pressure of the .380 be an issue in a conversion of .32?

Old Fuff
December 9, 2006, 02:11 PM
No, the pistol is more then strong enough to handle either cartridge. The .380 did come with a stiffer recoil spring though.

If one had a 1903 (.32) pistol, and wanted to completely rebuild it into a 1908 (.380) they could do so, if they had the knowledge, skill, and parts to do it. But his would involve modifying the frame in most cases, and a .380 slide with internals would be recommended. Then a .380 magazine would be required, as well as a new recoil spring, and possibly an ejector - this at a minimum.

Browning designed the pistol to be a .32 caliber. Colt brought out the .380 version later, and over decades ignored possible problems until in November, 1944 the U.S. Navy filed a complaint. That they couldn't overlook or sweep under a rug.

So does this mean that all of the .380 pistols are suspect? No, because Colt's usually meticulous hand fitting made up for any design flaws.

December 9, 2006, 02:17 PM
I would not ever trust someone who says they "rewarded" a pistol, and can't spell voila, to work on a gun, not even something as simple as replacing grip panels.

Jim K
December 9, 2006, 08:09 PM
Wow! I started this post to say that I didn't believe the pistol magazine well was simply filed out on the .32 frame to take the .380 magazine.

But I measured the mag wells, and then noticed that the frame on either side was the same thickness. How could that be, unless the frame itself was wider? So I measured the frames and slides of .32 and .380 pistols, and got a surprise.

Not only is the .380 magazine wider and the magazine well wider than those of the .32, the frame is wider, as is the slide. The slides will usually interchange due to the tolerances in manufacturing, but it is clear to me that they are different. Conventional wisdom has it that Colt simply took the .32, installed a new barrel, made some small changes, and produced the .380 version. Not true. Not only are the magazine and magazine well sized specifically for the .380, the whole gun is different, made for the larger cartridge.

So, here are the measurements, .32 first, followed by .380:
Width of magazine: .423" - .439"
Magazine well width: .435" - .446"
Magazine well length: .1.070" - 1.129"
Frame at rails: .615" - .629"
Slide width: .767" - .779"

Conventional wisdom, hell, they are different guns! Colt didn't just do a quick barrel change, they made a whole new gun, specifically tailored for the .380.


Old Fuff
December 9, 2006, 08:34 PM
Usually when Colt made a different frame they would assign a different letter to identify the model - this to insure things didn't get mixed up in inventory. It gets more interesting because in 1944 Colt couldn't (or wouldn't) provide an Army/Navy inspection team with a set of blueprints. The parts it seems were made to guages, not prints. The military services bought them as an off-the-shelf item.

I'll do some more research, and we need to measure some more guns. I know that .380 slides have been fitted to .32 frames.

Jim: Were the frames and slides you measured made during the same era (or within the same decade?)

December 9, 2006, 09:29 PM
Gents, I've posted on this before, and here are my findings......
had a 380 1908 with bad frame
purchased a 32 1903 parts gun

the 380 slide fit and worked on the 32 frame by changing the recoil spring and the mag disconnect plunger thingie plus mag.

the 32 slide DID not fit or work on the 380 frame.

Major difference in frames was the magazine safety disconnect feature.

Prof. A. Wickwire
December 9, 2006, 09:57 PM
I own a Colt 1908 in .380 ACP (1934 vintage). A standard Colt .32 ACP barrel works just fine with no other changes. Also, the standard .380 ACP 7-round magazine will hold and feed 8 .32 ACP cartridges.

I had no failures to feed, fire, extract, or eject while testing this theory.

Just my experience, your mileage may vary.


Prof. A. Wickwire

Old Fuff
December 9, 2006, 10:07 PM
Prof. A. Wickwire:
Jim Keenan:


If you would, please post the partial serial numbers of your .32 and .380 pistols. I am looking for evidence that there were dimensional changes made in the frame and slides between 1903 and 1945.

Prof. A. Wickwire
December 9, 2006, 10:24 PM
Old Fuff,

My Colt 1908 .380 ACP has a serial number of 1101XX. According to Colt Autos (http://www.coltautos.com/) it was made in 1932 (not 1934 as I stated above).

Please share your results with us once you have amassed the evidence you are looking for.


Prof. A. Wickwire

Mac Attack
December 9, 2006, 11:29 PM
So can I convert my 1908 .380 ACP to shoot .32 ACP by swapping the barrel and mag (or not) only? for what it's worth I have a Type III 1908 with a serial number of 59xxx.

Old Fuff
December 9, 2006, 11:59 PM
Well Jim sure did stir the pot.... :eek: :D

I've found some evidence that he may be right, but at the same time we know that in some cases a .32 to .380 conversion is possible. I'm less sure about a .380 to .32 set-up though. One issue is the ejector. Colt apparently used the same ejector on both guns, but if the larger .380 case hit the ejector to soon it could cause a jam. Colt got around ths by having final assemblers modify the ejector in .380 pistols when necessary, rather then stocking two different sizes. If one puts a .380 slide on a .32 frame that still has an unmodified .32 ejector there might be a problem. On the other hand if the ejector is opened up for the .380 case it might, or might not still work with the smaller .32's. Extractor hook fit might be an issue too. They were also hand fitted. To tell the truth, the whole gun was hand fitted.

The Old Fuff is a blabber-mouth of the worst kind. Of course he will tell all as the picture becomes clearer... :D

Jim K
December 10, 2006, 09:49 PM
I didn't say the slides wouldn't interchange. They did on the two pistols I checked, but the .32 slide was very tight on the .380 frame. It would have needed some fitting to really work right. I didn't check the ejectors. The .32 barrel will fit in the .380 slide but not vice versa, as the front lug is too big.

Old Fuff, the serial numbers are 158521 for the .32 and 59589 for the .380.

Want some more? I just miked a brand new USP .32, 570125, and its mag well dimension is the same as the older .32, but the frame and slide measurements are the same (within normal tolerances) as the older .380. Further, the frame thickness at the magazine well (which first attracted my attention on the older guns), is noticeable thicker than on the older guns. All of this indicates that eventually Colt went to the same frame (maybe under wartime pressures) for both calibers, but making the .380 mag well larger. Note that a .380 magazine won't fit in the USP .32, so there was still a difference in that area.

I will check out a couple of more when I get a chance, but been pretty busy lately.


Old Fuff
December 10, 2006, 11:14 PM
Ya, what I'm finding seems to go along with what you are saying. Perhaps the most important being that Colt serial numbered the .380's in their own series, starting in 1908 @ #1. If the frames were EXACTLY the same it seems certain that they would have been numbered in the .32 series on the basis they were interchangeable between the two models - but because of the magazine they weren't. Slides would have been easy to identify because they were marked with the intended cartridge. Some dimensional changes were made over the years, but the what and when wasn't too well recorded in the records - at least those that remain.

R.L. Wilson calls the .380, "a distinct model."

December 11, 2006, 09:24 AM
OK I'm going to wade in to this discussion,
I own a first generation Model 1903 #3039X,(That's ten choices as to which one it is guys),
I obliguarantee nobody is going to drop a 1908 .380 acp barrel in this pistol and make it work.

Now, if the seller had a late third or forth Model 1903 it is possible to fit a .380 barrel and magazine.
By 1940 or so Colt had fairly standardized the guns to the point the .380 and the .32 were about identical dimensionally.
Even so you can't just drop in a barrel and slap a magazine in place and make the pistol fire reliably.

The extractor cut out on the barrel must be identical to the extractor dimension of the slide one wishes to use.
The barrel must be fitted to the slide in a similar manner as one would fit a 1911 replacement barrel as should the bushing be fitted to the slide and barrel unless you have a late issue bushingless pistol and the you need to fit the muzzle to the slide port.

A 1903 Colt/Browning is not a 1910/1922 Browning, the magazines can not be interchanged as to cartridges, one must use a .380 magazine with a .380 barrel and a .32 magazine with a .32 barrel.
Using a the wider .380 magazine with the .32 cartridges and barrel will eventually cause the slide lock to wear excessively and fail.
Using .380 cartridges in a .32 magazine will place excessive strain on the feed lips and center seam of the magazine and eventually the magazine will spread and crack down the rear center, ruining a magazine that is already begining to become harder and harder to obtain.
Oh yeah, the slide lock is a seperate and distinct part between the .32 and the .380, this must also be replaced when attempting a caliber conversion.

Simple answer, can the caliber conversion be done on one of these pistols?
Within the Parameters, yes, it is feasible.
Did the seller do the conversion correctly?
Probably not.
What a waste of a decent and collectable pistol.

Old Fuff
December 11, 2006, 09:58 AM
Apparently you have an extensive collection of 1903/08 pistols. If you will measure the same dimensions as Jim Keenen did (see post #12) with matching partial serial numbers it would be very useful for our investigation.

... and the you need to fit the muzzle to the slide port.

Do you perhaps mean the breech end to the slide port?

...the slide lock is a seperate and distinct part between the .32 and the .380, this must also be replaced when attempting a caliber conversion.

This pistol does not have a slide lock as such, as the slide is locked back using the manual safety (aka "slide lock safety"). Are you perhaps refering to the ejector?

Thank you for your interest.

December 11, 2006, 10:12 AM
Very interesting and enlightening thread here.

I have a Colts 1908 hammerless serial #12120*. I purchased the pistol in the mid 80's. I bought a 32 barrel and mags for it back then, and the gun functioned perfectly with the 32 set up in the 1908.

Hope that serial range helps in the thread. Lots of knowledge being passed in this thread, looking forward to the resolution/findings by others.


Old Fuff
December 11, 2006, 11:28 AM
At least one .380 was converted to a .32 at Rock Island Arsenal, using the original frame and slide (the slide was re-stamped to show the correct cartridge). I presume, but can't confirm, that they changed the magazine to a .32 size.

Over the years a number of minor dimensional and cosmetic modifications were made to the 1903/08 pistols. In some of these cases the changes and dates were recorded, and the details are known. Apparently in other instances this was not the case, and may have been overlooked by later researchers. Depending on the date of manufacturer, a conversion from .380 to .32 may be more practical then the other way around. In any case one major roadblock would seem to be that an unmodified .32 ejector may cause stovepipe jams in a .380, and one modified to be used in a .380 may strike the .32 casehead too far out. Also in all of these pistols both the ejector and extractor were hand-fitted, as was the whole gun for the most part. Thus parts that are purchased from Numrich/Gunparts Corporation for example, that were removed from otherwise scrapped guns and originally fitted to those guns, may not work correctly in another - at least not without retrofitting. Clearing making a conversion is not a "drop-in" sort of thing unless Lady Luck smiles on you..

Jim K
December 11, 2006, 08:03 PM
Hi, guys,

I am doing some more measurements on Colt pocket hammerless pistols and slowly going nuts. The dimensions are all over the place. I will try to persevere and come up with something coherent. If you don't hear from me, contact the mental health people. I will be the guy sitting in the corner mumbling about .470" and .779" and 130769 and .32 caliber and stuff like that.


Old Fuff
December 11, 2006, 08:39 PM
Dr. Fuff believes that there is a correlation between the dimensions and when the gun was made. If we can survey enough guns vs. dates-when-mfg. some sense may come out of this. Also the outside dimensions of frames and slides may vary because of metal removed during polishing.

December 11, 2006, 08:48 PM
I have a 1903 32 ACP. I am not sure why anyone would want to change such a nice old gun. Leave it the way it is and be glad in 20 years when you can pass it on to your youngster.

Mine came from great great grandpa, grandpa, dad, me.

I'm glad no one tinkered with it.

Old Fuff
December 11, 2006, 11:53 PM

Not to worry... :)

The "converting" we are discussing won't harm the gun, and in a few minutes after switching some parts it will be exactly the same as it was. I don't believe any of us would want to hurt what is a fine old pistol, but there is no reason to not do things that would increase its usefulness. Any modificatons that have to be made would be done on the new parts, and not the ones that came on the pistol.

If you post the serial number of your pistol (use xx for the last two numbers) we can tell you some interesting stuff, like the year it was made.

December 12, 2006, 08:39 AM
This is what happens when one works three jobs and has about an hour or two at most to do some posting on a message board,,,,,
I realized I was thinking and writing about both the Walther PP/PPK design and the Colt 1903 design at the same time about an hour after I posted and well on my way to job number two.

As such, please accept my whoops and my recommendations and observations about the Colt 1903-1908 hammerless conversions up to the point where I begin babbling about the slide lock.

Old Fuff
December 12, 2006, 09:44 AM
Ah so.....

Thank you for the explanation...

December 12, 2006, 02:41 PM
I have a colt 1902 in 38 ACP and a 1903 in 32ACP.

I am out of town now, but have a picture. Looks like the serial on the 1903 is 4270XX.

From what I looked up I think it was made in 1923.

Old Fuff
December 12, 2006, 04:15 PM
Yup, that pistol was indeed made in 1923, and is what collectors call a Type 2. It should also have an improved firing system, with a hammer that has a half-cock notch (to catch the hammer if it accdentally follows down) and a inertial type firing pin of the kind used on the larger .45 Government Model.

When you get home you can check to see if the half-cock feature is there by first being sure the pistol is unloaded, then pull the trigger to lower the hammer. Next, pull the slide back about 1/4 inch. See if the grip safety has popped out, and the manual safety can be engaged. If so, you have the improvements explained above. If the grip safety doen't pop out and you cannot engage the manual safety, you don't. The change occured at "about" serial number 422,000 so your pistol could be either way.

December 12, 2006, 06:41 PM
What is the opinion of pocket carrry of the 1916 vintage,1903 with a shell in the chamber and the safety disengaged.

I have heard opinions pro and con.. With the gun in a pocket holster and with the grip safety, I have always felt pretty safe, but I would appreciate the views of others.

Old Fuff
December 12, 2006, 07:10 PM
Can you have too many safeties...? :what:

Well anyway, back during the 1920's and 30's, the Shanghai Municipal Police, whose weapons policies were determined by William E. Fairbrain (of Fairbrain & Sykes Commando Knife fame) ordered .380 Colt pistols for his smaller sized Chinese officers. At the time, Shanghai was one of the world's hot-spots, going on the several-gunfights-a-night plan.

Anyway, Fairbrain ordered Colt to instal a small screw above the safety to lock it out! :eek: :eek: Thereafter his men went with the grip safety and nothing else. This was the case up to the beginning of World War Two, and history has not recorded that they had any problems. Jeff Cooper's followers would likely swoon if they knew though... :D

I would note that after 1923 these guns had a half-cock notch to catch the hammer if it should accidentally fall. Iggy's pistol is probably not so equipped.

I never carried (or carry) the pistol with the chamber loaded unless the manual safety is engaged, but to each his own. My quick draw is timed with an hourglass these days... ;)

December 12, 2006, 07:39 PM
This has alway bugged me... I have a verrry nice 36 vintage Colt and the older one that is pretty scruffy.. When I get the urge to carry one of these old sweethearts I always grab the old one.

I am sure the newer version is probably safer, but it's just too purty to scuff up..

I know.. my leg is kinda cute too... decisions, decisions!!!!:o

I am like Ol Fuff.. I'm slowin' down a wee mite in the fast draw bidness.. Sneaky is good!!!

Mac Attack
January 17, 2008, 02:49 PM
I picked up a .32 ACP barrel and it fit nicely in my Colt 1908/.380 ACP (ser. 59xxx). Also, as has been noted by other members, .32 rounds fit in a .380 magazine. I haven't had a chance to shoot my handgun yet, but plan to this weekend. One thing I noticed is the .32 barrel does not fit as tight as the .380 barrel in the slide and at the muzzle.

January 17, 2008, 03:56 PM
I saw a set in one of my dealer's cases. It was a 1903 with a complete .380 upper (slide, barrel, spring and 2 extra .380 mags) for $800 a couple of months ago. I was told that the original owner got the conversion from Colt so after they came out with the .380.

Mac Attack
February 5, 2008, 09:54 PM
I had a chance to finally shoot my Colt 1903 .32 ACP barrel in my Colt 1908 .380 ACP handgun. I shot 100+ rounds of factory .32 ACP using both my existing Colt 1908 mag and an aftermarket 1903 mag. I did not have a single problem using the conversion barrel with either magazine. Therefore, I would not even bother purchasing a 1903 mag.

Also, the accuracy of the .32 was exceptionally very tight and more pleasant to shoot than the .380. I actually shot the .32 better than I did the .380.

So it is possible to convert from a 1908 to a 1903 by just changing the barrel.

February 5, 2008, 10:44 PM
Old Fuff

A couple of things come to mind; in 1906, did Colt ask Mr. Browning to come up with a more powerful round for the Model 1903, and that in collaboration with William Thomas of UMC/Remington Arms, design such a cartridge, the result being the .380 ACP? And didn't Mr. Browning then spend the next two years modifying the Model 1903 to function with the new round, eventually resulting in the Model 1908? If this were so, then wouldn't it explain the different measurements and dimensions which would make interchangeability between the two models somewhat questionable. As you pointed out, Colt ran the Model 1908 with its own run of serial numbers; if it were just another caliber addition (as was common with their revolvers), then why didn't they run the serial numbers in with the Model 1903 production? It would seem that in early production, at least, the Model 1908 was a dimensionally different gun than the Model 1903.
There was also a story I heard about the .380s that the Shanghai Police used during the time you mentioned. It had something to do with a cut-out made on the magazines that were issued to the police officers. It seemed that some of the officers had a penchant for selling their issued ammunition on the black market. They would then replace those rounds with some dummy ones as to give the appearance that the magazine was still fully loaded whenever weapons inspection came around. Eventually the higher ups caught on to this "practice" and had the magazines modified so that the primers could be seen through the cut-out slot in the back of the magazine. I have no idea if this is true or not. Just a story I heard (and I saw a magazine so modified, but couldn't verify by whom, or when).

Old Fuff
February 5, 2008, 10:54 PM
So it is possible to convert from a 1908 to a 1903 by just changing the barrel.

Yes and no. As you discovered it sometimes works, and in my limited experience it is more likely going from .380 to .32 rather then the other way around. One overlooked issue with this conversion is that the ejector may be too far outboard to hit the smaller rim the way it should. Extractor's may also cause problems. But what works, works. On the other hand it can be an expensive failure when it doesn't.

February 6, 2008, 12:03 PM
AS I sit here typing this , I got three setting herein front of me. A .380 and two .32's. THe .380 mag willl slide in one but not the other of the .32's.The .380 mag is very tight in the .32 but will fit.

It fits in serial # 504xxx, but not in serial # 388xxx.

Mag well opening is .438" for the .380 and .428" and .410" for the .32's.

It feels like the slides would interchange with little fitting. The ,380 barrel is a little tight in the .32s but the .32 barrels fit right into the .380.

So it would apear that some might interchange and some might not.

The extractor in all guns appear to be the same. I would have thought the .380 would be shorter but it doesn't look to be. Since these are blow back guns unless the .32 is too tight to feed I don't see where it would be a problem..

Love these little pocket guns. Got five of them.

February 6, 2008, 12:26 PM
I doubt if its really possible. And if so, not worth it. Just get .380 if you like it that much. Just a suggestion.

If you enjoyed reading about ".32 Colt Conv. to .380" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!