An automatic injection device containing a pre-loaded charge of medicament for automatically administering the medicament upon actuation thereof, the device comprising: a housing; a medicament chamber (150, 350) having a first compartment and a second compartment, the first compartment containing a first medicament portion and the second compartment containing a second medicament portion to be mixed with the first medicament portion; a seal structure (160, 360) between the first compartment and the second compartment, the seal structure (160, 360) initially in a sealing condition that maintains the first compartment separate from the second compartment; a needle assembly (140, 340) that dispenses the medicament charge from the medicament chamber (150, 350), the needle assembly (140, 340) comprising a needle and a needle support (143, 343), the needle support (143, 343) for mounting the needle to the medicament chamber (150, 350), the needle support (143, 343) defining a needle assembly chamber having an inner surface that tapers radially inward as it extends axially forward toward a rearward end of the needle, the needle support (143, 343) forming a channel from the medicament chamber (150, 350) to the needle; and an activation assembly, wherein activation of the activation assembly causes (a) the seal structure (160, 360) to be converted from the sealing condition to a mixing condition, (b) the first and second medicament portions to be mixed, and (c) the mixed first and second medicament portions to be forced through the needle assembly (140, 340), characterized in that it further comprises an insert mounted in a forward end of the medicament chamber (150, 350) adjacent the needle assembly (140, 340), the insert defining a tapering flow pathway that tapers radially inward as it extends axially forwardly. a housing; a medicament chamber (150, 350) having a first compartment and a second compartment, the first compartment containing a first medicament portion and the second compartment containing a second medicament portion to be mixed with the first medicament portion; a seal structure (160, 360) between the first compartment and the second compartment, the seal structure (160, 360) initially in a sealing condition that maintains the first compartment separate from the second compartment; a needle assembly (140, 340) that dispenses the medicament charge from the medicament chamber (150, 350), the needle assembly (140, 340) comprising a needle and a needle support (143, 343), the needle support (143, 343) for mounting the needle to the medicament chamber (150, 350), the needle support (143, 343) defining a needle assembly chamber having an inner surface that tapers radially inward as it extends axially forward toward a rearward end of the needle, the needle support (143, 343) forming a channel from the medicament chamber (150, 350) to the needle; and an activation assembly, wherein activation of the activation assembly causes (a) the seal structure (160, 360) to be converted from the sealing condition to a mixing condition, (b) the first and second medicament portions to be mixed, and (c) the mixed first and second medicament portions to be forced through the needle assembly (140, 340), characterized in that it further comprises an insert mounted in a forward end of the medicament chamber (150, 350) adjacent the needle assembly (140, 340), the insert defining a tapering flow pathway that tapers radially inward as it extends axially forwardly.