Safety considerations require rifles equipped with tubular magazines to be loaded with flat nosed bullets only. This ensures that the cartridges will not ignite one another. While safe, these bullets travel only at moderate velocities. To address this, Sierra has added a series of features to promote reliable expansion. Two of the bullets offer a hollow point design in which a large frontal cavity promotes rapid expansion on impact. In the 30-30 and 375 Winchester bullets, Sierra offers a Power Jacket which features a series of "skives" cut into the mouth of the jacket which allow for greater expansion at lower velocities.