Gamma ray measurement is an important issue in nuclear technology, since it is widely used in industry, medicine, agriculture, education research, and some military applications. Gamma ray is also needed to build radiation protection, which is very useful for human health. When gamma radiation penetrates through shielding material, it generates two radiation components within or beyond the shield, namely: the uncollided and the collided photons. Therefore, the buildup factor is an important parameter for gamma ray measurement. Buildup factor is defined as the ratio of the total number of particles at a given point to the number of uncollided particles, at that same point. In this work, we evaluate the gamma-ray buildup factors for copper (Cu-29), as a function of energy, for 0.511, 0.662, 1.275 MeV, by using cesium and sodium radioactive sources. The results show that the value of energy buildup factor decreases with increasing gamma energy, and increases with increasing thickness. Moreover, it was found that at high energies (1.275 MeV), the absorption buildup factor is at minimum when the energy is at high level. The results also reveal that there is no contribution from the scattering photons to the value of buildup factor, in general, at low intensity levels, when the geometry structure is built well. While for bad geometry, the detector measures intensity, which is greater than that described by the main linear attenuation coefficient, because the scattered photons will be detected as well. All in all, in order to get rational results, a well geometry should be used for the future applications.