The m/58 can be found in two slightly different versions. The older has a primer which is a bit rounded in the edges and
the primer is marked with ‘SM’ for the Svenska Metallverken factory. The cartridge does not have a lacquer seal around the
case mouth and the primer. The newer variation has a flat modern form primer and does have a lacquer seal around the case
mouth and primer.
The change of designation from m/58 to m/73 has been puzzling for many collectors over the years. There is no way to see
any differences in the cartridge from the outside. The only difference was the years of production shown on the cartridge
headstamps. So why was the cartridge re-designated with a new model number? There are no negative reports, for example,
of bad accuracy such those of the 9x20mm ammunition in 1948. In that instance the modification of the projectile, which
was totally redesigned, did not even lead to a new model number. The only thing changed between the two models of .38
Special ammunition was the type and amount of powder. This modification did not result in any changes in either pressure
or velocity. Both cartridges are, by definition, identical.
m/58
NC 688 0,25 gram (Ca 3,8 - 3,9 grains)
Pmax 1300 bar = 130 MPa
Velocity V0 240 m/s with a 2" barrel, with 4" V0 265 m/s
Projectile weight 9 gram
m/72
NC 1066 0,38 gram (CA 5,8 - 5,9 grains)
Pmax 130 MPa
Velocity V0 240 m/s with a 2" barrel, with 4" V0 265 m/s
Projectile weight 9 gram
A possible answer to this question came by personal comments from a former employee at the Carl Gustafs Stads
Gevärsfabrik in Eskilstuna. He stated that there had been a production error with some m/58 ammunition which had resulted
in some lots having been loaded with higher (perhaps double) charges of powder. This resulted in way too high of operating
pressures for any .38 caliber weapon and especially for the aluminum framed m/58 revolvers. The same individual also stated
that he had seen several demolished revolvers being turned in for salvage before the ammunition was withdrawn from use.
As it may not have been known which production lot or lots were in error, it appears that all m/58 ammunition was withdrawn and
in order to avoid any future confusion new production replacement ammunition that was designated as m/72.
What the Amkat catalogs show is that the cartridges are generating the same pressures and velocities, but are using two
different powders with different weights. This also was a possible indication of a loading error thus making the need in
changing the designation of the cartridge. As the Amkat states that the powder used in the original m/58 cartridge
is of less volume (0,25 gram or approximately 3,8 - 3,9 grains) compared to the m/72 that uses 0,38 gram (app 5,8 - 5,9
grains). To get a better indication, one cartridge of each model was pulled (m/58 headstamp 59 26, 1959 production by
Svenska Metallverken Västerås and a m/72 headstamp 74 027, 1974 production by Norma factory) and the grade of the fill
was inspected. While the results were informal but as an indication, with the use of a caliper the depth of the case and the
seating depth of the projectile was measured. The cases were then refilled with the fill measured in millimeters without
taking any corrections for the primer pocket (equal in both cases) nor the cavity of the projectile with a total depth of around
1,5 mm. With the data in hand, a simple conclusion could be made (but still not to be seen as any positive proof).
Case inner height: 25,5 mm
Seating of projectile into case: 8,5 mm
Space in case: 17 mm
Visual inspection of the powder shows it has the same approximately size and form of the grains.
Left, m/58 and to the right m/72.
Powder fillrate of m/58: 7 mm
Powder fillrate of m/72: 12 mm
A form of conclution?
One can easily see that a double load of the m/58 cartridge powder is roughly 14 mm and with the inner space of 17 mm it
does fit. Taking a double load of powder for the m/72 it gives a fill of 24 mm which is almost a full case of 25,5 mm and
not enough remaining space to seat the projectile in any proper way.
Packages
The .38 Special boxes are of the same type used over the production years with no changes between the physical designs of
the m/58 and the m/72. The boxes are produced are of a white cardboard with black print. The box is of a drawer type with
internal grid supporting walls for each cartridge
The production lots that I have identified from m/58 and m/72 box examples are as follows:
m/58:
026 59 02 27/2
026 59 05 29/4
026 59 05 29/5
026 61 001 21-4
027 67 7001 30-6
027 69 001 xx/5
027 72 001 (Headstamp of cartridges 027 69)
m/72:
027 74 001 19/9
027 75 002 04/08
027 75 002 10/10
027 76 001 15/6
References:
Amkat 1975
Amkat 1976
