Take your outdoor rifle or designated marksman setup to the next level with the powerful ACM M140 AEG Spring (SP140)! Constructed from high-tensile, heat-treated spring steel wire, this main power spring delivers high-velocity output in the range of ~440 to 470 FPS (depending on air seal tightness, barrel length, and build configuration). Featuring an advanced non-linear (variable pitch) winding design, it reduces initial startup strain on your motor and battery while releasing maximum kinetic energy to push heavier BBs through long distances. Designed for upgraded Version 2, Version 3, and quick-change gearbox systems, the ACM M140 is a reliable, high-output power upgrade!
United Kingdom
| TYPE | HOW MUCH? |
|---|---|
| Standard | £0.00 |
| Expedited | £4.99 |
| TYPE | HOW MUCH? |
|---|---|
| International | £14.99 |
Boost your muzzle velocity and gain a distinct competitive edge during long-range outdoor games with the ACM M140 AEG Spring (SP140)! Engineered as a high-power drop-in upgrade for Airsoft Electric Guns (AEGs), this main drive spring supplies the force required to punch through light foliage and maintain flat, high-velocity trajectories at long engagement distances.
High-Tensile Alloy Steel & Non-Linear Winding Forged from premium heat-treated alloy steel, the ACM M140 spring is specially tempered to maintain consistent tension without sagging, shortening, or suffering spring fatigue after thousands of high-stress cycles. It features a non-linear (variable pitch) coil layout that distributes spring spacing unevenly along the steel body. This design allows the motor and gear set to overcome lower resistance during the initial stage of the piston pullback, significantly decreasing battery drain and startup torque strain on your motor. Once fully drawn back, the tightly wound coils compress to release explosive, repeatable forward thrust against the piston assembly.
High-Velocity Field Performance & Ground-Flat Ends When installed in an AEG build featuring efficient air seal components and tight-bore inner barrels, an M140 rating generates approximately 440 to 470 FPS (tested using standard 0.20g BBs). This higher energy output makes it an ideal choice for outdoor field rifles, heavy-BB setups (.28g–.36g), and entry-level DMR builds. Both ends of the spring are ground flat to sit completely flush against bearing spring guides and piston heads, preventing spring binding, rotational twisting, and uneven lateral pressure inside the gearbox cylinder.
Universal Gearbox Fitment Manufactured to standard airsoft main spring dimensions, the ACM M140 is universally compatible with standard Version 2, Version 3, Version 6, and quick-change spring gearbox shells. Note: Due to the increased tension of an M140 spring, it is recommended to pair this item with reinforced metal gearbox shells, high-torque motors, steel gear sets, and steel-tooth pistons. Power up your build with the long-lasting performance and value of the ACM M140 AEG Spring (SP140)!
| SKU | 614232 |
|---|---|
| Brand | Double Bell |
| Weapon Category | Parts |
| Recoil | No |
| Shell Ejecting | No |
| FPS | 401 - 500 |
| Spring Type | AEG |
Our courier partners deliver from Monday to Friday, excluding Bank Holidays. We will attempt to dispatch all packages within 24 hours, although at peak times this may take slightly longer. Orders with products with two-tone service or Defence Check may take longer to dispatch.
Once the order is dispatched you will get an email with the tracking number and which courier partner it’s going to be delivered via. Any missing/incorrect items need to be reported with 48hrs of signed delivery.
Click Here to Download the Returns Form (PDF Format)
Faulty Product?! Unfortunately that is part of life but be rest assured we are here to help! Contact one of our friendly staff via phone or email. Stating what the problem is, if we can resolve the problem via phone or email great if not then they will advise how to send it back and what details we require.
FAQs
1. What is a BB gun used for? BB guns are mostly used for practice shooting and training. The stronger ones (i.e. Air Rifles) can also control pests or hunt small animals.
2. Do you need a Licence in the UK for a BB gun? No, you don't need a licence for a BB gun in the UK, but there are rules. The BB Gun needs to be in two colours; one has to be a primary. All our guns are on the website as per default.
3. Is a BB gun a good weapon? BB guns, despite sometimes being seen as toys, can be dangerous. They fire pellets at high speeds and can cause serious harm, or even be deadly in some situations.
4. Can you shoot BB guns in public in the UK without a Firearm license? BB guns in the UK navigate a legal grey area. While certain models, notably low-power 'soft air' types, typically evade classification as section 1 firearms, more potent versions may require a valid firearms certificate to avoid legal repercussions.
5. Can you shoot a BB gun in your garden? You can use a BB gun in your garden under UK law, but you have to ensure the pellets don't go into your neighbour's yard, plot or land. If they do and you don't have permission, it's against the law.
6. Which UK law am I breaking if the pellets go into my neighbour's law without permission? If your BB gun pellets go into your neighbour's yard without permission, you're breaking UK laws. Specifically, the 1968 Firearms Act and possibly the 2003 Anti-Social Behaviour Act, because you may be causing your neighbours trouble or worry.
Discover our five top selling BB guns under £30 guide here.
Discover our top selling Gel Blasters guide here.
Discover our Gas guns guide here.
Discover our Toy BB guns guide here.
Discover our five top selling BB guns of 2026 guide here.
Discover our top selling BB gun assault rifles guide here.
Discover our six top selling full auto BB guns (best BB machine guns to buy) guide here.
Discover our Top 6 airsoft pistols guide here.
Visit our High Wycombe Store
All items in Stock in our High Wycombe Store
01753 299 777 
