7,62 NATO pressure?


#1

I am trying to solve a trouble about the 7.62 NATO cartridge pressure limits.

The max pressure for a service round is listed 50000 psi on several books and 60190 psi according the EPVAT standards. I doubt these pressures were measured with the same method. So, what is the pressure limit listed in STANAG documents?

Do you know the pressure level of a 7.62 NATO IF measured with CIP equipment?

I know that the STANAG 9 mm Para sheet reports the pressure limits according the NATO and CIP method


#2

I can only report a few actual measurements of Bundeswehr DM41 / DM111 in CIP equipment, using Kistler piezo, 15 rounds each:
bar
2770 – FN 60 (Lot 2 60)
3080 – MEN92E0004
3087 – MEN94C0005
2795 – MEN95B0001
3028 – DAG93A0305

CIP Maximum is 4150 bar. Keep in mind that CIP used a case drilled 25 mm ahead of the base while EPVAT measurement is at the case mouth.


#3

The Polish firm of Mesko advertise the following figures for the 7.62x51 Ball:

  1. “Work-hardening” method of measurement (whatever that may mean): max/mean chamber pressure = 379/345 MPa

  2. Piezo-electric method: 400/365 MPa


#4

Thanks all,
JPeelen, I suppose that those pressure measurement where taken using the EPVAT method, am I right?

Tony
Does Mesko produce 7.62 mm ammo certified as “NATO loading”?


#5

No Pivi, the measurements I quoted were by a civilian institution in a CIP barrel.

Edit: I might add that Mesko commercial .308 Winchester with 9.45 g FMJ as sold in Germany 2013 was measured yielding 3108 bar (or 310.8 MPa if you prefer) by the same lab. Velocity 819 m/s from the 600 mm CIP barrel.

Edit2: My notes say that U.S. MILSPEC C46931F for the M80 cartridge specifies 50000 PSI maximum average pressure with a copper crusher and 365 MPa or 52940 PSI in an EPVAT barrel.


#6

[quote=“Pivi”]
Does Mesko produce 7.62 mm ammo certified as “NATO loading”?[/quote]

I’m not sure but I assume so: the bullet type and weight match the M80, they provide a NATO stock number, and give a list of weapons for which the ammo is suitable (G3, MG3, FN FAL, FN MAG, SIG Sauer, UKM 2000).


#7

For the U. S. 7.62x51mm M80 cartridge, chamber pressure is specified in MIL-C-46931F. See: mil-spec.tpub.com/MIL-C/MIL-C-46 … F00005.htm

MIL-C-46931F includes both copper crusher and EPVAT methods. NATO EPVAT testing procedures require the piezo pressure transducer to be mounted ahead of the case mouth. I doubt anyone in the civilized world still uses the copper crusher method, even though it remains “legal.”

I have no idea what the STANAG 2310 says. I do know that the maximum CIP chamber pressure (.308 Win.) is 60,192 psi, but I do not know exactly what the term “maximum chamber pressure” means under CIP. I believe CIP uses a piezo gauge but the “maximum” pressure could be an average pressure plus some number of standard deviations or the highest individual round chamber pressure measured of some prescribed sample number of rounds tested. In any event, CIP maximum pressure is not comparable to that from NATO EPVAT due to the large difference in pressure test procedures (conformal vs. case mouth).

I am assuming, very possibly incorrectly, that CIP and SAAMI pressure test procedures and instrumentation are more or less identical, incorporating a conformal piezo pressure gauge. However, maximum pressure standards differ slightly, with SAAMI establishing 62000 psi as a maximum, while CIP’s maximum is 60192 psi. I’ve never seen a side-by-side comparison of chamber pressure profiles of exactly the same cartridge as determined by SAAMI, CIP and NATO EPVAT methods. That would be interesting.


#8

DennisK, as far as I know evene SAAMI and CIP use slightly different methods.
CIP method requires an hole in the case, 25 mm form the rim, whereas SAAMI method doesn’ìt require to drill the cartridge. Slightly different maximum levels are due to this fact


#9

That’s very comprehensive, except that when quoting the velocity to be achieved it doesn’t specify the barrel length. Would this be the 24.5" of the M240 or something else?


#10

Mesko’s “Work Hardening” method is the old “Copper-Crusher” system, which Measures CUP, and NOT atmospheres or PSI etc. The CUP figures have then to be converted to “normal” Pressure Units…That is why everybody uses Piezo-electric Methods Now, even though there is still the difference of Sensor Positioning ( Drilled case or Case Mouth) This difference catches the pressure change at different Points in the Powder Combustion Cycle…the Drilled Shell from Ignition through to Bullet exit,. but the Case Mouth system only records from the moment the Bullet clears the Bleed Hole at the case Mouth, so the initial Primer ignition pressure, Initial flame up of Powder, and then the rapid rise in In-Case pressure is not recorded…only the High Pressure ( and subsequent drop) as the Bullet is released from the Neck seal and enters the Leed of the rifling.( another spike here as well).

Kistler is a general maker of Piezo-electric transducers for all sorts of industrial applications, from Internal combustion engines to Jet and rocket engines to Ordnance ( both SA and Artillery).

The Former company of AV-Link, of Graz, Austria, made a range of Chronograph/Pressure Measuring devices for the Various Ammo Factories and Laboratories world wide…they also did Prototype MB Engine testing at their Graz Facility ( Saw it in 1996, during a Visit). Their Small arms Pressure system was really stand alone and Portable. ( I saw them in operation at Sellier & Bellot, Vlasim, during the same trip)
and the Best “Value for Money” if one knew what to get. Sadly, this company no longer exists ( Financial problems).

Doc AV


#11

Tony, the STANAG prescribes test barrel lenght as 22.0 inches. I am quite sure the U.S. specification is the same. (Sorry for the late answer.)


#12

Thanks!