By Bruce Simpson
It seems that every couple of weeks we get a message here
wanting to know if the Norinco 7.62x39 FMJ ammo is
corrosive. I mentioned here a few months ago that I was
going to perform some simple tests in an effort to ascertain
this.
I performed a test on
the Norinco 7.62x39 FMJ ammo that I bought recently and it
certainly produced no corrosion.
NOTE: The ammo I
refer to is copper-washed steel (case and bullet) with
steel-cored bullets which is sold in case-lots (wooden) of
1200 rounds. Inside the case the ammo is boxed up into
yellow cardboard containers with a styro-foam
insert (20 rnds/box). Each round is stamped with the
characters: 311 (or maybe 3II) and 92. The
cardboard boxes clearly state that this ammo is non-corrosive
(but I didn't believe that until I'd tested it for myself).
This test consisted of shooting a couple of hundred rounds
through my SKS then scraping the residue from inside the gas
tube and piston onto one of three plates of plain steel.
One of the other plates had common salt sprinkled on it and
the other was left untouched.
Prior to the test all three plates were scrubbed and degreased
then dried in an oven at 200 deg Celsius for 30 minutes.
After the salt and powder residue was applied, all three
plates were again baked for 20 minutes at 200 deg Celsius and
then removed and left out in my garage for three days (it's
summer here and the temp has varied from about 15 deg C at
night to 25 deg C during the day and we have had rain on two
of the days).
After the three day period I observed the following
results:
PLATE 1 (the control, untouched steel)
Small spots (pinhead size) of rust were observed on the
surface of this plate.
PLATE 2 (sprinkled with common salt)
Spots of rust were noticeable. These spots were somewhat
larger than those of the control plate and were more obvious
where the crystals of common salt were concentrated.
PLATE 3 (powder residue)
In areas exposed to the air (ie: not covered in residue) the
rust patterns were identical to the control plate (ie: small
pinheads) Where the metal was covered by the powder residue
however, the steel was *LESS* affected by rust although there
was an even layer of "tarnish". This tarnishing was
certainly not as deep as the pitting produced by the rust
spots found on
the exposed areas on all plates. It would appear that
(in this case) the residue was almost providing a barrier
between the air and the steel and a level of protection from
rust.
CAVEATS:
This was hardly a carefully monitored "lab-level"
experiment and despite the fact that we had a couple of small
showers of rain during the test period, the humidity overall
was quite low during the three days the plates were left
exposed.
Testing was forced to a conclusion on day 3 when my wife
"tidied up" the exposed plates, contaminating the
salt and residue covered ones by stacking them face-to-face on
my bench.
Since this experiment seemed to confirm that the ammo is
non-corrosive I've taken to cleaning my SKS with conventional
techniques and materials. Now I just use Hoppes #9 on
the barrel and gas-system. The first time I did this I checked
every day for a week to make sure that no corrosion was
occurring. None was found and a re-clean on the fifth
day resulted in clean patches first time through with not a
hint of rust.
DISCLAIMER:
Since Norinco seem to be packaging their 7.62x39 ammo in a
number of ways (stripper clips, galvanized boxes, green card
& wax paper, yellow cardboard & styro-foam , etc) I'm
not about to put my head on the block and say to everyone that
it's safe to assume *all* this ammo is non-corrosive.
All I'm saying is that the batch I've got seems to offer no
threat to the life of my rifle when I use normal cleaning
techniques.
