AR-15 Stock – UTG PRO Ops Ready S4 Mil-Spec – Compact 4-Position
PLEASE DOUBLE CHECK DETAILS AND FITMENT BEFORE PURCHASE.
The UTG PRO Ops Ready S4 is a compact AR-15 mil-spec stock system built for lightweight, low-profile rifle setups. It is designed around a short 4.28-inch stock body, 4-position adjustment, a rubberized butt pad, a slanted cheek rest, and a removable extended cheek rest insert for a more controlled shoulder weld.
Choose the stock-only version if you already have a compatible mil-spec carbine receiver extension. Choose the full stock kit if you need the stock plus the tube, buffer, spring, end plate, and castle nut. Same S4 attitude. Different level of parts in the box. Don’t buy the kit if all you need is the stock. Don’t buy the stock-only version if you still need the guts.
Variant Options
| Package | Finish | What You Get |
|---|---|---|
| Stock Only | Black | S4 polymer stock with cheek rest, removable extended cheek rest insert, rubberized butt pad, sling loop, and reversible sling swivel housing. |
| Stock Only | Flat Dark Earth | S4 polymer stock with cheek rest, removable extended cheek rest insert, rubberized butt pad, sling loop, and reversible sling swivel housing. |
| Stock Kit | Black | S4 stock plus mil-spec extension tube, buffer, buffer spring, receiver end plate, and castle nut. |
| Stock Kit | Flat Dark Earth | S4 stock plus mil-spec extension tube, buffer, buffer spring, receiver end plate, and castle nut. |
Fitment
- Fits AR-15 rifles using a compatible mil-spec adjustable carbine receiver extension / buffer tube setup.
- Stock-only variants are intended for rifles that already have the correct mil-spec tube installed.
- Stock kit variants include the mil-spec extension tube, buffer, buffer spring, receiver end plate, and castle nut.
- The stock uses a compact 4-position adjustment design and is built for low-profile rifle setups.
Does NOT Fit
- Does not fit commercial-spec buffer tubes.
- Does not fit fixed rifle-length receiver extension setups.
- Does not fit AR-10/LR-308 platforms unless the specific receiver extension setup is verified compatible.
- Stock-only variants do not include the extension tube, buffer, spring, end plate, or castle nut.
What It Does
- Gives compatible AR-15 rifles a compact adjustable stock setup.
- Provides a slanted cheek rest and removable extended cheek rest insert for a more consistent shoulder weld.
- Uses a rubberized butt pad for better shoulder contact.
- Includes a reversible sling swivel housing for left- or right-handed sling setup.
- Keeps the rifle trim without hanging a giant boat anchor off the back end.
Why It’s Worth It
The S4 makes sense when you want a shorter, cleaner AR-15 stock without losing the basics that matter: adjustability, cheek support, sling options, and a proper butt pad. The stock-only version is the smart move for an existing mil-spec setup. The kit version is the clean grab when you need the stock and the hardware to complete the rear end.
Specs
- Brand: Leapers / UTG PRO
- Product Type: AR-15 stock / stock kit
- Model: Ops Ready S4
- Fit: AR-15
- Tube Compatibility: Mil-spec adjustable carbine extension
- Stock Positions: 4-position
- Stock Length: 4.3 inches / 109 mm
- Height: 4.80 inches / 121.92 mm
- Width: 1.66 inches / 42.2 mm
- LOP Adjustment Increment: 0.625 inch / 15.9 mm with mil-spec carbine extension tube
- LOP Collapsed: 10.2 inches / 259 mm with mil-spec carbine extension tube
- LOP Extended: 11.5 inches / 292.1 mm with mil-spec carbine extension tube
- Stock-Only Weight: 5.7 oz
- Stock Kit Weight: 15.5 oz
- Material: Polymer stock body; stock kit includes aluminum/polymer components
- Finish Options: Black or Flat Dark Earth
What’s Included
- Stock Only: S4 stock, slanted cheek rest, removable 5.51-inch extended cheek rest insert, rubberized butt pad, reversible sling swivel housing, and standard sling loop.
- Stock Kit: S4 stock, slanted cheek rest, removable 5.51-inch extended cheek rest insert, rubberized butt pad, reversible sling swivel housing, standard sling loop, mil-spec extension tube, buffer, buffer spring, receiver end plate, and castle nut.
Install Notes
Install should be handled with the correct AR tools and basic armorer knowledge. If you are installing the stock kit, confirm the buffer system, receiver extension, castle nut staking needs, and safe function before live fire. Cheap guesses make expensive lessons.
Verify Before You Buy
- Confirm your rifle uses a mil-spec adjustable carbine receiver extension.
- Confirm whether you need Stock Only or the complete Stock Kit.
- Confirm your chosen finish before checkout.
- Confirm all local, state, and federal rules regarding firearm configuration before installation.
Disclaimers
⚠ Trademark & Compatibility Disclaimer
IronKells Armory LLC is not affiliated with, endorsed by, or sponsored by any manufacturer mentioned. All trademarks are the property of their respective owners and are used only to identify compatibility or fitment.
⚠ Install & Compatibility Disclaimer
Installation should be performed by a qualified armorer or gunsmith. Improper installation, modification, or use may affect firearm safety and reliability. Buyer is responsible for verifying compatibility, performing proper function testing, and ensuring safe operation.
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