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The ProMag RM40 fills a real need for folks who want more capacity without stepping into larger, bulkier setups. Holding 40 rounds of 5.56 NATO or .223 Remington, this magazine gives you 10 extra rounds over a standard 30-rounder, which means less time spent reloading at the range and more time putting rounds downrange.
ProMag's roller follower design is the key here. Instead of a flat follower, small wheels on the RM40's follower roll across the magazine body as you fire. This cuts down on friction and binding during the feed cycle, which helps rounds move up reliably without getting stuck. The DuPont Zytel polymer body is molded to spec with crimped feed lips that hold rounds securely in place.
The magazine spring comes from heat-treated chrome silicon wire, which is tougher than standard spring material. ProMag rates these springs to stay loaded and stored for up to six years without losing tension or developing weak spots. That's useful if you're the type to keep mags staged or stashed for extended periods.
This is a solid choice for regular shooting sessions where reliability and affordability matter. The RM40 works with any standard AR-15 platform rifle chambered in .223 Rem or 5.56 NATO. At 10.25 inches long with a black finish, it's small enough to fit in a pack or range bag without taking up much space. ProMag backs the magazine with a lifetime manufacturer's warranty, and the entire unit is made in the USA.
The roller follower has small wheels that roll along the magazine body instead of sliding flat. This cuts friction during the feeding cycle and helps prevent binding or nose-diving of rounds, which can cause feeding failures. The reduced friction is especially useful when the magazine is fully loaded.
Yes. ProMag designed the RM40 with a heat-treated chrome silicon spring that resists fatigue. The magazine can remain loaded and stored for up to six years without the spring weakening or losing tension. This makes it good for staged mags or emergency supplies.
The RM40 is designed for standard AR-15 platform rifles chambered in .223 Remington or 5.56 NATO. It should work with most modern AR-15s, though fit can vary slightly between different manufacturers. Testing it in your specific rifle before relying on it is a smart move.
ProMag backs the RM40 with a lifetime manufacturer's warranty against defects in materials and workmanship. If you experience a failure due to a manufacturing flaw, you can return it to ProMag for replacement.
| UPC | 708279012549 |
|---|---|
| Manufacturer | |
| Manufacturer Part Number | RM-40 |
| Brand Fit | AR-15 Platform |
| Caliber/Gauge | .223 REM/5.56 NATO |
| Capacity | 40 |
| Length | 10.25 |
| Model | |
| Model Fit | AR-15 |
| Package Height | 2.0 |
| Package Width | 5.5 |
| Product Type | Accessory-Magazines |
| Shipping Weight | 0.45 |
| Quantity | 1 |
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