Is this a .38 AMU case?


January 9, 2004, 10:12 PM
Sorting through my never-finished pile of .38 Special brass, when an oddball catches my eye. Look carefully at the round on the left. There's a deep extractor groove, and semi-rimmed. The round on the right is a standard .38 Special for comparison. The headstamp of the round on the left says WESTERN 38 SPL SR, which I assume to be Short Range. The round on the right says WIN NT 38 SPL, which I suppose is the version just prior to WIN 2K, which in itself was a precursor to WIN XP. (Dunno, really, what the NT means, either) Take a look, I'm guessing the left round is a .38 AMU, but I'm open to suggestions:


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January 9, 2004, 11:10 PM
Not sure what it is,but a 38 AMU was a bottlenecked cartridge (45 ACP necked down).
I think it is an early 38 Super case.Please correct me if I'm wrong:scrutiny:

January 9, 2004, 11:22 PM
Way too long for that. A .38 Super case is 0.900" long, as opposed to this thing, which mikes 1.155".

Supposedly, the .38 AMU, or the .38 AMU I'm thinking of, is the round developed in the early 1960's for the Army Marksmanship Unit, for use in their specially-chambered 1911's, and the relatively few S&W Model 52's that were also chambered for it. It fired a flush-seated hollow-base wadcutter not unlike the standard .38 Special HBWC target loads I shoot in my own S&W Model 52.

I've seen the .38-45, a necked-down .45 ACP, but I've never heard of that wildcat referred to as the .38 AMU.

January 9, 2004, 11:50 PM
I know I've got the info in one of these books.........just don't remember which one.
I'll look this weekend if no one else weighs in.

Old Fuff
January 10, 2004, 12:31 AM
The case on the left is indeed a .38 AMU (Andvanced Markmanship Unit) cartridge. It was originally loaded with the same .38 wad-cutter bullet used in the .38 Special mid-range target load. Same with the powder charge. The "SR" in the headstamp stands for "semi-rimmed" not "short range."

It was an attempt to get around problems getting the regular rimmed .38 Special to feed reliably from a box magazine. Colt made a conversion kit consisting of a slide with a breechface and extractor designed for the .38 AMU as well as a barrel chambered for the cartridge. Military armorers used these to build the guns. S&W also made a handful of model 52's, I think for the army. I don't believe any of these guns or ammunition were offered for civilian sales - at least not many. Eventually military teams started using their .45's in the Centerfire Matches and the .38 AMU project passed into history. I'm suprised you found one at a shooting range recently. I'd expect them to be gone by now.

January 10, 2004, 12:41 AM
Buddy gave me a bunch of brass from his serious shooting days in the early 1960's. I got a big batch of "Police Only" .357 Magnum Super Vel brass, too! This .38 AMU gets a special place in my cartridge collection wall display rack. ;)

Old Fuff
January 10, 2004, 01:09 AM
I see ............

Well I think you have a good idea, you aren't likely to find any more outside of what you have now.

Now if you could find an original pistol to go with it .......

January 10, 2004, 07:22 AM
.38 AMU, rather rare, nice thing to add to one's case collection.

January 10, 2004, 11:20 AM
I stand corrected!
I did see a 38 AMU chamber reamer on eBay sometime last year though.So I guess some were in civilian hands at some point.
Thanks for the info,Robert.

Jim K
January 10, 2004, 08:31 PM
IIRC, there was some civilian interest in the .38 AMU and even though the army did not sell guns or ammo to civilians, gunsmiths did make guns for it (converted .38 Super Colts, mainly) and reamers were (maybe still are) available. Cases were made simply by trimming the rims of .38 Special and cutting an extractor groove; loads were standard .38 Special wadcutter.


Johnny Guest
January 21, 2004, 03:02 PM
- - That's what you got. Also known as, and in Win-Western production, headstamped as, ".38 Special Semi-Rimmed."

I've seen a lot of custom-turned .38 Spl cases, and a few with military headstamps (WRA 67) but very few of the "38 SPL SR" type.

Good catch. I don't THINK I've ever handled a loaded round.


January 21, 2004, 03:27 PM
I got a .38 AMU commercial Colt converted by Jim Clark to .38 Special midrange wadcutter. So apparently the guns were sold on the civilian market to some extent.

January 21, 2004, 04:22 PM
Yep; I've got a loaded wadcutter round with that exact headstamp in my cartridge collection. The "NT" on the Winchester case next to it stands for "Non Toxic" meaning the bullet, the primer, or both were made with lead-free materials; if you look close, the flash hole may be a little larger than on normal cases, because they had a variety of problems with the early NT primer compounds.

Paul "Fitz" Jones
February 3, 2004, 12:45 AM
I have been a reloader since 1952 and have a lifetime collection of brass I am inventorying to sell off. I have some of the semi rimmed cases mentioned here. Is there a place for cartridge collectors or head stamp collectors?

A Call to Arms
March 24, 2007, 10:09 PM
The 38 AMU is not a 45 APC necked down to .38" it is a rimless verision of the 38 Special loaded with a wad cutter projectile. The AMU is for (Army Marksmanship Unit) The .38 AMU was manufactured by Colt from a .38 Super frame and has .38 Super serialization with a .38 AMU conversion kit slide. The Army took .45 frames and assembled their guns using .38 AMU kits with a blued finish. For more Information see our site at ( we sell collectible ammunition to collectors! Thanks, Dave

November 25, 2010, 08:20 AM
Not sure what it is,but a 38 AMU was a bottlenecked cartridge (45 ACP necked down).
I think it is an early 38 Super case.Please correct me if I'm wrong

You're thinking of a wildcat cartridge that attained some popularity some years back. It was just called the 38/45 if I recall correctly, and had nothing to do with the .38 AMU.

Actually, it was not a bad idea, and, in some ways was the precursor of the .357 SIG.

It did away with some of the feeding problems of a .45 ACP.

November 25, 2010, 11:19 AM
I bought a used 38 Super Colt 25 years ago that had been converted to 38 AMU. It even had a magazine stamped 38 AMU. Unfortunately, I converted it back to 38 Super before I knew what 38 AMU was.

The necked down to 38 caliber 45 ACP goes by several names but is frequently called the 38/45 Clerke or 38/45 ACP. It was developed in the early 60's by Bo Clerke. It was supposed to improve feeding over a 38 special wadcutter round and allow the competitor to shoot his M1911 just by changing the barrel and recoil spring.

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