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The 18 inch version is exactly 35.64 oz on my kitchen scale. An average lighter profile barrel like this looses about 1 to 1.5 oz per inch you cut off, so the 16 will most likely be somewhere between 32.5 and 33.5 ounces.
The barrel is 7.62. However, it is generally accepted by most that you can fire 308 or 7.62 ammo in either chamber. 308 and 7.62 are not identical in terms of rated pressure, but they are so close as to make no practical difference (ie: if 58kpsi doesn't blow the gun up, 62kpsi should not blow it up either).