.
The 300 Improved AMU (AMU for Army Marksmanship Unit) was made by
re-forming the Weatherby 300 Magnum, with a steeper bottle-neck angle, and
slighly longer case body.
It is very easy to confuss the 300 Improved AMU with the 300  Ackley Magnum
Wildcat, (note the 300 AMU has a slightly longer case body before the start of the
bottleneck (2.375" vs 2.179"), & longer O.A.L (2.78 vs. 2.60").
300 Improved AMU
.
.
above 3 different
300 AMU
300
H&H
300
Weathby
A
M
U
R
E
M
-
U
M
C
3
0
0
H
&
H
3
0
0
W
e
a
t
h
b
y
A
M
U

W
C
C
60
Out
of
Stock
.
.
Winchester
WCC 61
Head Stamp
1961
FMJ
$ 7.50 per
Cartridge
.
A
M
U

W
C
C
61
.
.
To the best of my knowledge
this should be considered an
obsolete Military Proprietary
Cartridge.
Both Remington & Winchester
loaded cases for the AMU.
300 AMU
300 Ackley
300 REM-UMC
Head Stamp
197 Grain H.P.
MATCH
.
$ 7.50 per
Cartridge
out
out
Out
of
Stock
out
out
Military Cartridge Stock
.