T91 80% finishing - some lessons

[darkarmour]

The I finished my 80% recently and thought I'd share some small issues I ran into

1. In my receiver, the front pivot pin detente pin channel (in which the detente and spring go) was too shallow -- about 5mm too shallow. This interfered with the pivot and spring assembly so much that it was impossible to depress the detente fully (which is required to install the front pivot pin). The solution was to drill the channel some more, to match the depth present in my other lower receivers. This had the additional benefit of deburring the channel. If you do this, be sure to flush thoroughly with lubricant.

2. My lower receiver parts kit (from T91 Tactical) came with the ROC mil-spec selector. I milled the fin off, per the standard instructions. But I found that despite milling the fin off, the selector was still interfering with the trigger slab; for instance, if the selector was very slightly off-center from 90 degrees, the hammer would fail to drop or, more frequently and much more dangerously, would drop with a 0.5 to 1-second delay. This is obviously very dangerous.

To fix this, I had to plane down the relevant (now-flat) selector surface significantly, both in the middle of the selector and towards the side walls, with the goal of clearing all interference whatsoever.

[darkarmour]

Here is my finished build.

AJpIGvv.jpg

[Womper]

Looks great!! I can’t wait to get my lower done.

[e292644]

Looks great, thanks for sharing!
Here's the update for modifying the T91 safety selector.

SafetySelectorMod3.jpg