The saiga most resembles an AK-74 and the AK-100 series of rifles. It includes a stamped receiver, and 90-degree gas block unlike the AK-47 which has a milled receiver and 45-degree gas block. The use of a third trunnion rivet gives it resemblance to the AK-100 series of rifles Russia is currently exporting. This rivet is not present on the AK-47, AKM, and AK-74, the bullet guide in these designs incorporate an extra appendage which allows the bolt to lock while this Saiga and AK-100's use a single rivet design. Most of the components of the Saiga are similar if not identical to an AK-101, but there are many cosmetic and functional differences between a Saiga and an AK series rifle. On the Saiga there is a pin that is used to secure the front hand guard on to the front barrel assembly and a screw that is used to secure the hand guard in towards the rear. The 7.62×39 version Saiga is unable to accept standard AK-47 (7.62×39, 5.45×39, 5.56×45) magazines; physically the magazine catch will not allow a magazine to lock into place inside of the receiver. The Saiga's magazine catch has a smaller clearance between the receiver than a “normal” AK. This does not allow the larger lug of a non-Saiga magazine to lock in. The AK type magazines can be modified to lock in place, but cartridges may not feed because the Saiga's receiver lacks a bullet guide. The bullet guide allows a round to be pulled from a magazine and then fed into the chamber without being caught on the front trunnion; this bullet guide is specifically built on the lip of the Saiga magazine. Any magazine used that does not have this feature may not feed reliably in the rifle. Another difference of some later model Saigas is that they have a bolt hold open button. The Saiga bolt hold open is engaged by manually pressing a lever near the trigger guard and pulling the charging handle rearward although this feature does not automatically hold the rifle's action open after the last round is fired as seen on the AR-15. Most versions of the rifle lack a pistol grip and don't have a threaded front sight block, making it unable to accept muzzle devices. The trigger and trigger guard of most of the US versions are placed farther back on the receiver than on a typical AK series rifle, and a transfer bar type system is used to release the hammer. This results in the Saiga to have a considerably heavier and grittier trigger pull than that of other Kalashnikov-made firearms.