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Home / Pistols / Springfield Armory Hellcat OSP / Holosun 407K X2

Does the Holosun 407K X2 fit the Springfield Armory Hellcat OSP?

Yes, with an adapter plate: the Hellcat (RMSc footprint) → Holosun 407K / 507K from C&H Precision.

Adapter plate required

The slide isn't cut for this pattern. One plate adapts it, listed below. The plate supplies the recoil posts the optic sits on.

  • Hellcat (RMSc footprint) → Holosun 407K / 507KC&H Precision ↗$25–60C&H makes a separate version for the EPS / EPS Carry / SCS Carry.
Same answer forThe Holosun 407K X2 goes on the Springfield Armory Hellcat Pro the same way: it shares this slide's optic cut.
SlideSpringfield Hellcat OSP cut (Micro footprint)
Optic footprintHolosun K
Optic screwsper plate maker · T10
Optic torqueper plate maker (15 in-lb is the optic maker's figure for mounting it straight on a slide)
Plate to slideper plate maker
Cost to mount$175–360

New to red dots? What footprint, plate, co-witness and the rest mean →

Will your iron sights co-witness?With standard-height irons: No co-witness. Standard-height irons sit well below any pistol red dot window and are only usable with the optic off. Suppressor-height sights fix that; a different optic won't.With suppressor-height irons: Marginal. Suppressor-height irons usually co-witness with an open emitter on a direct cut, but a plate raises the optic and can put the front sight at or below the bottom of the window. Check the plate's deck height before ordering sights. This optic's window runs small (19.5 × 14.7 mm), so a front sight slightly off the ideal height is more likely to miss it. That's the typical case for this kind of optic, not a guarantee: pistols don't standardize sight and optic heights the way rifles do.
How this slide mounts an opticMilled for what Springfield calls its Micro footprint, the Shield RMSc pattern: an RMSc-pattern optic, Springfield's own Hex Wasp included, bolts straight on. A Holosun K optic takes a plate: C&H says its plate is what lets a 407K or 507K go on without modifying the slide's recoil posts. Source: C&H Precision, Hellcat to Holosun 407K / 507K ↗.
GuidesShield RMSc vs Holosun K: which optic fits which cut · Suppressor-height sights: will your irons co-witness? · Red dot lost zero? Troubleshooting the mount

What to order, and how to fit it

The fit checker's build sheet for this pair, assuming sights of unknown height. Open it in the fit checker to set your sights, work out screw length from your own caliper readings, or copy it as text.

Rather not do it yourself? Mounting an optic is a short bench job for most gun shops and gunsmiths. Buy the parts under "Parts to order" and take this sheet with you.

Build sheet

Data compiled September 2026 · Optic Mounting
Pistol
Springfield Armory Hellcat OSP
Optic
Holosun 407K X2
Footprint
Holosun K
Slide
Springfield Hellcat OSP cut (Micro footprint)
Mount
Adapter plate required

Parts to order

1 ×Holosun 407K X2Holosun K footprint · 6 MOA$150–300
1 ×Hellcat (RMSc footprint) → Holosun 407K / 507KC&H Precision — C&H makes a separate version for the EPS / EPS Carry / SCS Carry.$25–60
1 setSuppressor-height sights, if yours are standardMeasure your front sight first, then compare it with the sight heights published for this slide and optic, where the sheet lists them. The height that co-witnesses depends on the slide and the optic; a slim slide needs less than a full-size one.optional
Estimated total: optic + plate$175–360

Where to buy

Holosun 407K X2Holosun K footprintHolosun ↗
Hellcat (RMSc footprint) → Holosun 407K / 507KC&H PrecisionC&H Precision — this item ↗
Suppressor-height sights, if yours are standardOptional, for a co-witness. Makers include Trijicon, Ameriglo, XS and Dawson

Fasteners: which bag

You don't buy these. Screws come with the pistol, the optic and the plate, and they look alike. The thread is tapped into the slide or plate (the optic only has a clearance hole), so they decide the thread, not the optic.

JointThreadComes from
Plate → slideM4 × 0.7Supplied with the plate.
If your pistol shipped with a cover plate, keep its screws apart from these: plate screws and cover-plate screws are different lengths.
Optic → plateper plate makerSupplied with the plate, not the optic.
Most mistakes happen here. The screws in the optic's box are cut for mounting straight onto a slide; a plate changes the stack, so the plate maker supplies the right pair. If your plate came without screws, measure before you buy.

On the bench before you start

  • Torque wrench — set to the figure in your optic's manual
  • Driver bits — T10, fully seated so they don't round the head
  • Calipers — for the screw length check below
  • Blue removable threadlocker — Vibra-Tite VC-3 or Loctite 242. Never red.
  • Degreaser — isopropyl or brake cleaner
  • A parts tray — you'll have three bags of look-alike screws
  • Witness-mark paint or lacquer — so you can see if anything moves later

Install spec

Plate to slideper plate maker
Optic torqueper plate maker (15 in-lb is the optic maker's figure for mounting it straight on a slide)
Screwsper plate maker
DriverT10
Interface2 screws, 2 forward lugs (rear posts omitted)

Sequence

  1. Clear the pistol. Drop the magazine, lock the slide back, look and feel the chamber, then do it again.
  2. Remove the factory cover plate and set its screws aside. They are not optic screws.
  3. Degrease the slide pocket, both faces of the plate and the optic base. Oil under a plate lets it move.
  4. Seat the plate on the slide, check it sits flat with no rock, and fit its screws with blue threadlocker.
  5. Torque the plate to spec, bringing the screws up evenly rather than one at a time.
  6. Seat the optic on the plate's recoil posts, fit the optic screws with blue threadlocker, and torque to the optic spec.
  7. Let the threadlocker cure before firing (check the bottle; usually a few hours to overnight).
  8. Confirm zero at your working distance, then re-check torque after the first 100–200 rounds.

Before you fire it

  • Screw length checked dry: it must not bottom out on the slide or reach the striker channel.
  • Optic sits flat with no rock, and the screws pulled up evenly.
  • Torque set with a wrench, not by feel. Witness-mark the screws so movement is visible later.
  • Threadlocker cured.
  • Function check, then zero confirmed live.

Screw length is the one that hurts

Too long and a screw bottoms out on the slide or reaches the striker channel; too short and it strips under recoil. This sheet gives the thread but can't give the length, which depends on your exact plate and optic stack. Test-fit dry and count threads.

Sight co-witness

Confirm the firearm is unloaded before any work on the slide. Mounting an optic is gunsmithing: stay within your competence and use a gunsmith when a job is past it. Provided as-is with no warranty; you use this at your own risk. Prices are approximate street-price bands from September 2026. Torque and fitment figures come from manufacturer documentation; confirm against the current manuals for your pistol, optic and plate before installing. Not affiliated with or endorsed by any manufacturer.

The Springfield Armory Hellcat OSP with other optics

Every optic on the Springfield Armory Hellcat OSP, and how each mounts →

The Holosun 407K X2 on other pistols

Every pistol the Holosun 407K X2 fits →

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