This page was first published online 5-12-2007
This page was last updated 5-12-2007
(Note: On this page, as throughout this website, the term "38 Super" refers to the 38 Super +P cartridge.)

The 38 Super is a straight-walled semi-rimmed cartridge.  Its physical dimensions are identical to the old 38 Automatic cartridge from which it originated. The maximum overall length of the case is .900 inches, and the maximum overall length of the loaded cartridge is 1.280 inches.  The SAAMI (Sporting Arms and Ammunition Manufacturers Institute, Inc.) dimensions for this cartridge are shown in Figure 1. The SAAMI bullet diameter for the 38 Super is .356 inches. The SAAMI barrel bore diameter is .346 inches while the barrel groove diameter is .355 inches.

Note: This is a partial list of the SAAMI specifications, though the most relevant ones are shown. The SAAMI booklets can be purchased at www.saami.org.

The minimal rim of the 38 Super (.406 inches) is called a semi-rim because it is not as wide as the rim that revolver cartridges possess, but is significantly wider than the case body (.384 inches). The semi-rim was intended to headspace the cartridge just like revolver cartridges. But this turned out to be detrimental to accuracy (Speer Reloading Manual), and many (most?, all?) modern barrel makers headspace the 38 Super from the case mouth as is common with most other semi-automatic pistol cartridges. In recent years a rimless version of the 38 Super case has been developed. More information on rimless cases can be found on the Brass page of this website.

The 38 Super is a straight-walled case in the purest form with no taper for the length of the case. This is almost the only common semi-automatic cartridge that can make that claim. The other semi-automatic cartridges, 32 Automatic, 380 Automatic, 9mm Luger, 40 S&W, 10mm and 45 ACP all have some taper, though it is negligible in some cartridges, amounting to no more than 0.001 inch (see references below). Only the tiny 25 Automatic stands with the 38 Super with a straight-walled case.  A majority of revolver cartridges, on the other hand, have straight-walled cases.

Cartridge Measurements

Most of the dimensions listed in Figure 1 (above) are Maximum dimensions and the actual measurements of cartridges are a wee smaller than the SAAMI specifications. Actual measurements from some factory ammunition are shown in Table 1. The accompanying figure shows the key to the measurements. One case of each brand was measured for the outside dimensions. Overall length is an average of several cartridges. No doubt there is variation between cartridges and lot number. All loaded cartridge dimensions fell within the maximum SAAMI specifications. However, bullet diameter did not always match the SAAMI standard of .356 inches because most of the factory ammunition examined was loaded with .355 inch bullets (also see the Factory Ammunition page).

Table 1: Some 38 Super Factory Ammunition Dimensions (inches)

Manufacturer
Case Headstamp
Bullet* & Shape
A
B
C
D
E
F**
G
Aguila
AGUILA
130 RN
0.400
0.338
0.895
1.268
0.381
0.381
0.355
American Ammunition
A-MERC
115 RN
0.402
0.342
0.893
1.255
0.382
0.382
0.360
CORBON Match
R - P
140 FN
0.402
0.341
0.895
1.235
0.381
0.381
0.355
CORBON DPX
R - P
125 FN
0.401
0.341
0.896
1.262
0.381
0.381
0.355
Federal
F C
130 RN
0.402
0.341
0.896
1.271
0.381
0.382
0.355
Fiocchi
G.F.L.
129 RN
0.402
0.340
0.894
1.269
0.382
0.382
0.355
Magtech
C B C
130 RN
0.403
0.342
0.894
1.251
0.380
0.381
0.356
PMC
P M C
115 FN
0.401
0.341
0.895
1.184
0.380
0.380
0.355
Remington
R - P
130 RN
0.402
0.341
0.897
1.261
0.382
0.381
0.3555
Winchester
WIN
130 RN
0.401
0.342
0.894
1.270
0.380
0.380
0.3555
Winchester
WIN
125 FN
0.402
0.339
0.898
1.268
0.380
0.382
0.357
SAAMI Maximum Dimensions
0.406
0.345
0.900
1.280
0.384
0.384
0.356

* Bullet weight in grains. ** Measured just behind the case mouth to avoid measuring the "crimp" dimension. This is addressed in the Crimp section (coming soon). R - P = Remington Peters. WIN = Winchester. FC = Federal Cartridge. FN = Flat Nose; hollow point or flat point. RN = Round Nose. Note: CORBON uses cases made by different manufacturers. Some of their Glaser Safety Slugs were loaded in Winchester brass. The average of 2 bullets. See the Factory Ammunition page for more information on American Ammunition.

Pressure

Pressure refers to the peak pressure produced by the expanding gases as the gunpowder burns in the cartridge case. This pressure pushes the bullet through the barrel bore. If the pressure is not high enough, the bullet could get stuck in the barrel. If the pressure is too high, the gun might be damaged and the shooter injured.

The 38 Super is a very high pressure pistol cartridge. It has substantially more pressure than the old 38 Automatic cartridge it originated from. The SAAMI Maximum Average Pressure values are shown in Table 2. Values are shown via two different measurement techniques, CUP and psi (see explanation below).

Table 2: SAAMI Maximum Average Pressure Standards

Cartridge
psi*
CUP
25 Auto
25,000
18,000
32 Auto
20,500
15,000
380 Auto
21,500
17,000
9mm Luger
35,000
33,000
38 Special
17,000
17,000
38 Automatic
26,500
23,000
38 Super
36,500
33,000
9X23 Winchester
55,000**
-
357 Magnum
35,000
45,000
40 S&W
35,000
-
10mm Auto
37,500
-
44 Magnum
36,000
40,000
45 ACP
21,000
18,000

All values (except 9X23 Winchester) are from ANSI/SAAMI booklet Z299.3-1993. American National Standard. Voluntary Industry Performance Standards for Pressure and Velocity of Centerfire Pistol and Revolver Ammunition for the Use of Commercial Manufacturers. 1993. Sporting Arms & Ammunition Manufacturers' Institute, Inc., Wilton, Conn. USA. Not responsible for typographical errors. * psi = pounds per square inch. CUP = copper units of pressure. ** I wrote to Winchester's technical support and asked specifically what the maximun average pressure limit was for the 9X23 Winchester cartridge. On 4-13-2009 the Winchester Technical Department responded and stated that the pressure limit was 55,000 psi.

Pressure standards in the United States are based on two different measurement techniques, a copper crusher that produces Copper Units of Pressure (CUP), and a piezoelectric system that measures pressure in pounds per square inch (psi). The method used in Europe is controlled by the Commission Internationale Permanenta, or CIP. The European methods uses a transducer like the piezoelectric system, but by different methods, and loads developed by the CIP system might be different than those developed by the SAAMI protocols. (Speer Reloading Manual #13). I don't pretend to understand anything about how these systems work but will try to very briefly summarize some of the information presented in the SAAMI manual and the Speer Reloading Manual #13. By the way, The Speer manual is intelligently written, with over 120 pages of information on handloading basics, safety, troubleshooting, and explanations of how it all works. It is recommended reading. No, I have no affiliation with Speer, it's just a very good manual.

The copper crusher system is older than the piezoelectric system. The crusher system "determines pressure by correlating the amount that a cylinder of copper is crushed to the pressure of the expanding gases." The test barrel's chamber has a hole in the side, and a copper cylinder of known metallurgy is one of several parts aligned with(in) this hole. When the cartridge is fired the pressure crushes the copper cylinder to some degree. The cylinder is measured and compared with calibration factors to determine the amount of pressure required to compress the copper cylinder a given amount. The value is expressed as Copper Units of Pressure (CUP) (SAAMI manual and Speer Reloading Manual #13).

The piezoelectric system uses a transducer with a piezoelectric crystal mounted in the cylinder wall. When the cartridge is fired, the strength of the electrical signal is proportional to the amount of pressure. The pressure values are expressed as pounds per square inch (psi) (SAAMI manual and Speer Reloading Manual #13).

The SAAMI manual lists the Maximum Average Pressure limits for the 38 Super and most other handgun cartridges in both CUP and psi values. Handloaders should note that these are the MAXIMUM pressure limits for these cartridges. Loading manuals always recommend that these pressure limits should never be exceeded. This is good advice since exceeding these pressures can result in case rupture and damage to the gun and injury/death to the shooter and bystanders. That said, the 38 Super has been pushed beyond these pressure standards for use in some shooting sports, notably IPSC practical shooting, which allows cartridges of this caliber to qualify for a higher scoring paradigm in "Open" classification if they meet certain power standards. Experts question the safety of this practice, and this is recommended ONLY in guns with special ramped barrels that offer full support of the case. This practice is NOT recommended for guns with conventional, unsupported feed ramps because they do not fully support the cartridge case (ramped and conventional barrels). This is discussed in more detail in the Major Power Factor Ammo section (here) of this website.

Note: The author made two attempts (April 20, 2007 and May 1, 2007) to contact SAAMI by email (rpatterson@saami.org) and requested permission to post Figure 1 on this website. They did not respond to my emails. In the presence of no response, I posted Figure 1 on 5-12-2007.
References:

Speer Reloading Manual #13. 1998. Ed. Allan Jones. Blount, Inc. Sporting Equipment Division. Speer, Lewiston, ID.

ANSI/SAAMI booklet Z299.3-1993. American National Standard. Voluntary Industry Performance Standards for Pressure and Velocity of Centerfire Pistol and Revolver Ammunition for the Use of Commercial Manufacturers. 1993. Sporting Arms & Ammunition Manufacturers' Institute, Inc., Wilton, Conn. USA.

Winchester Ammunition Reloader's Manual, 15th Edition. 1997. Winchester Group, Olin Corporation, East Alton, IL, 62024.

Questions, comments, suggestions, hate mail? Feel free to email me. However, the probability of getting a response is low simply because I have a day job and a life and don't have the time to respond to all emails. It's nothing personal, really. Nevertheless, I do appreciate your thoughts. If you see an obvious error then please put the word ERROR in the title of your email. Thanks, and happy shooting.
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