ISMS Picatinny scope mount rings and red-dot interfaces screw size
M4 · length not stated in the sources
Our records put ISMS Picatinny scope mount rings and red-dot interfaces on M4 screws. None of the sources we found gives an exact length, so measure the original before you order.
The record covers manual states M4 Torx-20 screws for rings and optic interfaces (Aimpoint Micro, RMR, Deltapoint).
Head and drive, as the source states them: Torx T20 drive.
This entry is marked confirmed and comes from gunsmoke.eu.
An M4 screw is 4 mm in diameter with a 0.7 mm pitch, tapped with a 3.3 mm drill; imperial look-alike: #8-32 (4.17 mm) — the standard US PC/rack screw, close but not the same.
ISMS Picatinny scope mount rings and red-dot interfaces screw specifications
One row per fitment record. Head, drive are shown only where the source states them; pitch is the ISO coarse pitch for the thread.
| Thread | Length | Pitch | Head | Drive | Where it goes | Status |
|---|---|---|---|---|---|---|
| M4 | not stated | 0.7 mm | not stated | Torx T20 | Manual states M4 Torx-20 screws for rings and optic interfaces (Aimpoint Micro, RMR, Deltapoint) | Confirmed |
Fitment records and sources
Manual states M4 Torx-20 screws for rings and optic interfaces (Aimpoint Micro, RMR, Deltapoint)
pitch 0.7 mm · tap 3.3 mm · clearance 4.5 mm · PH2 / Torx T20
How to check the screw before you buy
- Do not confuse metric mounting screws with the 1/4-20 or 3/8-16 tripod threads that cameras and clamps also carry.
- Diameter: across the threads an M4 screw measures about 4 mm with calipers (usually a hair under). If yours measures noticeably more or less, it is a different thread.
- Pitch: 0.7 mm from one thread crest to the next (14.29 crests per centimetre). A thread pitch gauge or the pitch-gauge tool settles it in seconds.
- Length: measure from under the head to the tip for pan, button, wafer and cap heads; countersunk (flat) heads are measured overall.
- Driver: the source names a Torx T20 drive. For comparison, standard M4 heads take PH2 (Phillips) or T20 (Torx), or a 3 mm hex key.
- Tightening: no device-specific torque is published in these records. The site's general figure for M4 is about 2.0-3.0 N·m into metal threads and 0.8-1.4 N·m into plastic bosses; snug it up and stop.
Common mix-ups with M4
- Ideal Scope Mounting System manuals disagree between revisions (M4 vs M5 clamping screws) - check your own manual.
- There is no single standard Picatinny/rail screw size; makers use metric M3/M4 and imperial 6-48 or 8-40 interchangeably. Always measure the existing screw.
More in Cameras & Optics
The same screw also fits
Devices whose records share a thread with ISMS Picatinny scope mount rings and red-dot interfaces, closest length match first.
- Ideal Scope Mounting System rifle scope mount also M4
- Wimberley AP-600 / AP-604 lens foot plates also M4
- Holosun 507k/407k screw, Glock 43X/48 MOS shim plate also M4
- TS-Optics 2" Crayford focuser (Newtonian version) also M4
- SmallRig BSS2710 gimbal mounting plate also M4
- Celestron NexStar 8 eyepiece holder set screw also M4
- Newport M-FAM4 fixed angle adapter also M4
- Thorlabs CCM1-BS028/M 90:10 cage cube beamsplitter also M4
Questions about ISMS Picatinny scope mount rings and red-dot interfaces screws
- What size screw does ISMS Picatinny scope mount rings and red-dot interfaces use?
- M4 for manual states M4 Torx-20 screws for rings and optic interfaces (Aimpoint Micro, RMR, Deltapoint).
- How long are the screws in ISMS Picatinny scope mount rings and red-dot interfaces?
- None of the sources states a length. Remove one screw and measure it from under the head to the tip (overall for a countersunk head).
- What is the thread pitch of an M4 screw?
- 0.7 mm (coarse), which is the standard pitch for M4 machine screws; a 0.5 mm fine pitch exists but is uncommon. The tap drill is 3.3 mm and the normal clearance hole is 4.5 mm.
- What screwdriver do I need for ISMS Picatinny scope mount rings and red-dot interfaces?
- The source lists a Torx T20 drive. Standard M4 heads otherwise take PH2 (Phillips) or T20 (Torx), or a 3 mm hex key.
- Can I use an imperial screw instead of M4?
- No. Imperial look-alike: #8-32 (4.17 mm) — the standard US PC/rack screw, close but not the same. Use a true M4 screw so it does not cross-thread or strip the hole.