set screws 100 that secure the gas block 50 to the rifle barrel 20 looking into the gas block barrel bore 170 in fig9 shows the gas tube bore 70 in the gas block in contrast fig1 14 show details of the adjustable gas block according to the present invention fig1 and 13 show adjustable gas block assembly 110 showing the sliding adjustment plate 120 and detent pin spring 140 in the adjustable gas block 160 the front view of the adjustable gas block shown in fig1 shows the positional sliding adjustment plate 120 and the detent spring in relation to the barrel bore 180 while the back view shown in fig1 shows the relational position with the gas tube bore 80 in the adjustable gas block 160 similar to the prior art the adjustable gas block is attached to the barrel with set screws 100 as shown in fig1 fig1 and 16 are left and right perspective views respectively of the adjustable gas port assembly 110 showing the adjustable gas block 160 the sliding adjustment plate 120 the adjustment block alignment hole 200 and the adjustment gas block barrel bore 180 unlike the prior art gas blocks in a preferred embodiment of the present invention the adjustable gas block 160 includes adjustment block alignment hole 200 in the gas tube with the prior art gas blocks it is common for the gas block to be mis aligned with the barrel 39 s gas port some users don 39 t realize that you can install a gas tube after installing the gas block after the adjustable gas block 160 is mounted on the barrel 20 without the gas tube 30 installed prior to tightening the.