Drill Jig for SLR ZRO Series Handguards
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ZRO Jig
NOTE:
Not all Upper receivers have the same first picatinny block width.
For SLR see below
FOR AERO PRECISION go to bottom of page
Mount Jig flush with receiver so the bushing side hangs over the front and allows chips to clear.
25in lbs torque or moderately tight.
Now take the bit and mark with tape at 1.100”
You don’t want to drill too far and push drill through Picatinny rail .
Get bit spinning with lots of lube as it goes into bushing and into receiver.
7075 receivers are hard so drilling will take quite a bit of pressure.
Drill at high speed throughout the operation and use lots of lubricant on bushing and receiver.
Once you get to the marked spot on the drill remove drill from bushing while the bit is moving .
Remove jig and blow out bore to clean out any chips.
Test fit pin . You should have .270 thou of pin sticking out of receiver.
Pin may feel a bit loose but this is normal. Once all buttoned up it becomes bound up and is extremely solid.
Install barrel nut (no barrel yet) and slide HG onto nut with pin in place.
A rubber mallet will help tap the hg into place.
If you don’t get contact between the HG and receiver you can drill the difference by reinstalling the jig and drilling the distance needed.
The ZRO system is a tight fit. Pulling the hg back off usually involves a rubber mallet with some light taps to separate from receiver.
Or you can shorten the pin a touch.
Depending on the tools used , drill press or hand drill one of these options may be better for you .
Once satisfied with fit , install barrel and nut , gas block and tube along with muzzle device if applicable.
Then slide hg onto nut with pin in place.
Install wedges correctly, rubber wedges on muzzle end and smooth wedges on receiver end.
Tighten bolts to 35in lbs .
When tightening wedges the HG will pull down very slightly to level the HG and Receiver picatinny evenly as well as tensioning ZRO pin place.
FOR AERO PRECISION Upper receivers
Use the 3/8” pin (Silver short pin)
Drill into upper .100" only
Due to the thinner pic rail front block the short pin must be used.
Be careful not to drill through the pinactinny!
