Has anyone installed the T91 Front Sight Assembly?

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e292644
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Sat Sep 08, 2018 8:52 am

I would recommend following steps:

1) Remove the pin and press off the old gas block.
2) Clean and lightly smooth out gas port journal area, apply lubricant for press in the new block. If you experiencing tight fit, you may bore the gas block or use 500-1000 sandpaper polish the gas port journal area to get it fit. We use reamer to smooth out the front sight base.
3) Press in the new gas block, align with upper receiver. Fit your piston system and hand guard, mark retaining pin drilling point with masking tape or something similar.
4) In proper alignment, drill new retaining pin (3.0mm) use #2/0 Spiral Flute Taper Pin Reamer expand it and install the new pin.
5) Complete drilling of the gas port by doing 30 deg, 2.0mm 1st, then ream it with 2.2mm on the new gas block. Be very careful on this process. Go very very slow on rpm and feed or you will end up with broken drill bit inside the gas port. Use plenty of the lubrican.
KalashniKEV wrote:
Sat Sep 08, 2018 3:35 am
OK... so now that I have the new block in hand, I see exactly what you guys are talking about:

1) Complete drilling of the port by doing 30 deg, 2.2mm on the new gas block.
2) Remove the pin and press off the old gas block.
3) Press on the new gas block.
4) In proper alignment, drill new retaining pin (3mm) and install the wider pin.
MAYBE open up the gap on the bottom of the HGs.

Is that the job?


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codyphillips48
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Sat Sep 08, 2018 10:06 am

e292644 wrote:
Sat Sep 08, 2018 8:52 am
I would recommend following steps:

1) Remove the pin and press off the old gas block.
2) Clean and lightly smooth out gas port journal area, apply lubricant for press in the new block.
3) Press on the new gas block, align with upper receiver. Fit your piston system and hand guard, mark retaining pin drilling point with masking tape or something similar.
4) In proper alignment, drill new retaining pin (3.0mm) and install the new pin.
5) Complete drilling of the port by doing 30 deg, 2.0mm 1st, then ream with 2.2mm on the new gas block.
Only thing I see missing is taper reaming the barrel pin hole. The new pin is a taper pin. My gas block almost fell right on after cleaning up both the barrel journaling and gas block journal. Im gonna guess that's why it was hard for me to keep it straight.
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ZX672
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Mon Dec 30, 2019 5:13 am

e292644 wrote:
Sat Sep 08, 2018 8:52 am
I would recommend following steps:

1) Remove the pin and press off the old gas block.
2) Clean and lightly smooth out gas port journal area, apply lubricant for press in the new block.
3) Press on the new gas block, align with upper receiver. Fit your piston system and hand guard, mark retaining pin drilling point with masking tape or something similar.
4) In proper alignment, drill new retaining pin (3.0mm) and install the new pin.
5) Complete drilling of the port by doing 30 deg, 2.0mm 1st, then ream with 2.2mm on the new gas block.
Question on number 5. When you drill the new gas block and press back on, your 2.2mm port will align with the gas port on the barrel correct? I assume the gas port hole on the barrel is chamfered to allow some wiggle room?

I have not pressed of the original gas block so I just want to get an idea on what I should expect.
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