Torque driver
Inch-pound range, with the bits your screws take. The single most useful tool in this list and the one most people skip.
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The cheapest part of the system and the one that most often fails. Correct base, correct height, correct torque — in that order, with a level and a torque driver.
Where zeros go to die
The cheapest part, and the one that fails
When someone tells you a scope will not hold zero, the scope is at fault maybe a quarter of the time. The rest is mounting: the wrong base, the wrong height, uneven torque, no thread locker, a ring that was overtightened until it dented the tube. All of it is preventable with an hour of care and a torque driver that costs less than a box of premium ammunition.
Bases: what your receiver will accept
| System | Recognise it by | Notes |
|---|---|---|
| Picatinny (MIL-STD-1913) | Evenly spaced square recoil slots, 0.206" wide | The most flexible standard. Rings clamp into any slot |
| Weaver | Similar profile, narrower slots at irregular spacing | Picatinny rings often will not fit Weaver bases — check before buying |
| Two-piece bases | Separate front and rear pieces screwed to the receiver | Light and clean. Requires correctly matched pairs |
| One-piece base | A single rail spanning the receiver | More rigid, easier to level, slightly heavier |
| Non-gunsmithing (NGS) | Clamps to existing receiver features, no drilling | Popular on rimfires and some classic actions |
| Rimfire dovetail | Grooves milled into the top of the receiver, 3/8" or 11 mm | Common on .22 rifles. Needs dovetail rings, not Weaver |
Weaver versus Picatinny
They look nearly identical and they are not interchangeable in both directions. Weaver slots are narrower and unevenly spaced. Most Weaver rings will sit on a Picatinny rail; many Picatinny rings will not drop into Weaver slots. Measure before ordering, and on a hard-recoiling rifle make sure the ring's recoil lug actually engages a slot.
Ring height
Use the lowest rings that let the objective bell clear the barrel with a business card's thickness to spare, and that still let the ocular clear the rear sight or bolt handle. Lower rings mean a better cheek weld, a more repeatable head position and less holdover error at close range.
| Typical height class | Roughly suits | Confirm |
|---|---|---|
| Low | Objectives up to about 36 mm | Objective clears the barrel |
| Medium | 40 to 44 mm objectives | Also clears iron sights if fitted |
| High | 50 mm objectives, large tubes, AR-pattern rifles | You can still get a cheek weld without lifting your head |
Heights are not standardised between manufacturers, so a "medium" from one brand may be a "low" from another. The only reliable method is to measure from the base surface to the centre of the ring, or to test-fit before committing.
Torque values
Always use the values printed in your ring and base instructions — they vary by design and material. The figures below are the general ranges you will see, given so you know when something looks wrong, not as a substitute for the manufacturer's spec.
| Fastener | Common range | Failure mode if wrong |
|---|---|---|
| Base to receiver | Around 15–25 in-lb | Too loose: shifting zero. Too tight: stripped receiver threads |
| Ring cap to ring | Around 15–20 in-lb | Too tight dents or crushes the scope tube and voids the warranty |
| Ring clamp to rail | Around 30–65 in-lb | Too loose lets the whole assembly walk under recoil |
Mounting, in order
Degrease everything
Screw holes, screw threads, base underside and ring interiors. Factory preservative oil stops thread locker working and lets clamped parts slip.
Fit and torque the base
Blue medium-strength thread locker on the base screws. Tighten in a cross pattern to the specified value. Check the screws are not bottoming out into the bolt raceway.
Level the rifle
Clamp it in a rest and put a level on a flat receiver surface or the base itself, not the barrel. Everything after this depends on the rifle being genuinely level.
Set the ring bottoms and drop the scope in
Do not tighten yet. Slide the scope fore and aft until you have a full, black-edge-free image in your natural shooting position — on the rifle, in the position you will actually shoot from.
Level the reticle to the rifle
Use a second small level on the elevation turret cap, or hang a plumb line at 25 yards and align the vertical crosshair to it. A canted reticle throws shots sideways as distance grows.
Torque the ring caps evenly
A little at a time, alternating between screws and between rings, until you reach the specified value. Keep the gaps on both sides of each ring even.
Bore sight, then confirm on paper
Bore sighting gets you on the paper at 25 yards; it is not a zero. Fire, adjust, and confirm at your chosen distance. Re-check every screw after twenty rounds.
Do you need to lap the rings?
Lapping removes high spots so the rings grip the tube evenly, and it can help with inexpensive two-piece bases. On a quality one-piece mount it is usually unnecessary, and done badly it removes finish and material you cannot put back. If the scope shows even contact marks all round after mounting, leave it alone.
Kit list
What the job actually needs
Two small levels
One for the receiver, one for the turret cap. Or a purpose-made scope levelling kit that does both at once.
Thread locker
Blue, medium strength. Red is permanent and you will regret it. Let it cure before shooting.
Degreaser and a rest
Isopropyl alcohol for the threads and a stable rest or vise that holds the rifle level and still while you work.
Common questions
Mounting FAQ
How tight is "tight enough" without a torque driver?
There is no reliable answer, which is the point. Hand feel on small screws varies by a factor of three between people, and the consequences run from a wandering zero to a crushed scope tube. An inch-pound driver is inexpensive and removes the guesswork permanently.
Can I mount a scope on a rifle with no drilled holes?
Sometimes. Non-gunsmithing mounts clamp to existing features on certain receivers, and many rimfires have integral dovetail grooves. Otherwise the receiver has to be drilled and tapped, which is a gunsmith job — getting the holes square to the bore is not a garage task.
My scope is canted. Does it really matter?
Yes, and the error grows with distance. A canted reticle means your elevation adjustment is no longer purely vertical relative to gravity, so as you hold or dial for more drop you also drift sideways. At 100 yards you may not notice. At 500 you will.
Should I use a 20 MOA base?
Only if you need it. A tapered base tilts the scope down so more of its internal elevation is available for long-range dialling. On a normal hunting rifle zeroed at 100 to 200 yards it can leave you unable to come down far enough to zero at all.
Compare mounts, rings and tools
Confirm your base pattern, tube diameter and required ring height before ordering.
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