First Caveat - I am not a photographer. I was out cleaning guns this a.m. after a visit yesterday (and poor weather).
The Light looked good, so I took a few pictures of a unfinished Mod2 barrel, that I have up in NoVA to explain the Mod2 gas system to customers.
AN Fitting Straight Gas Tube:
What this does is give a leak proof seal on the gas tube to gas block. With the convention gas tube setup one needs to either seal the block to tube with 1) Heat Resistant Compound - like Rockset) 2) Significantly high tolerances on the block and tube 3) a combo of that or 4) Port the gun larger than really needed to ensure sufficient gas to cycle the action. If your over port the gun, your going to do two things, have even more gas port erosion and higher bolt carrier velocity when it erodes, as well as the block and tube will eventually seal and you run into even higher carrier velocity -- which beats the gun to death sooner than needed.
View of Gas Block Nozzle and Flared End on Gas Tube:
Barrel Notch and Gas Block Self Aligning Prow
To ensure all block will fit with all barrels - the gas block will self align on the barrel due to the shape of the notch -- with the taper pin system, a new block could not always be guaranteed to be bale to be mated properly with the old barrel which already had been drilled for taper pins on another gas block
Thread on Gas Block Retaining System:
Taper Pins, the bane of Engineers everywhere... The problem with taper pins, is that depending on how they are installed or re-installed, they can cause accuracy issues (as well as be scrapped or scrap out a gas block) you drive a metal pin into a metal barrel, and need to have enough tension so the pin is retained...
Metal is moving someplace - and pressures on the barrel are not generally good.
There are a few more benefits to this setup -- but here at least is a teaser for those who will be getting their Mod2 SR-15's shortly.