Description
The Radical Firearms RPR 5.56 is about as compact as an AR pistol gets before the whole idea stops making sense. Model FP75556M47RPR runs a 7.5 inch black Melonite threaded barrel inside an M-LOK RPR handguard, on a black anodized aluminum receiver with a full-length Picatinny rail, and it feeds from standard AR magazines at 30+1.
What you are buying here is a platform rather than a finished gun, and the price reflects that. The Radical Firearms RPR 5.56 ships with a bare pistol buffer tube and no brace, which keeps the cost down and lets you fit whatever you actually want rather than paying for something you will immediately replace.
Radical Firearms builds these in Stafford, Texas, and the company has made its name on exactly this: honest AR components at a price that leaves room in the budget for optics and ammunition.
Features of the Radical Firearms RPR 5.56
- 7.5 inch barrel in black Melonite, threaded at the muzzle
- M-LOK RPR handguard, so accessories mount directly without rail sections
- Black anodized aluminum upper and lower receivers
- Full-length Picatinny rail on the upper for optics
- 30+1 capacity, feeding from standard AR-15 magazines
- Black polymer pistol grip
- Bare pistol buffer tube, with no brace or stock fitted
- Right hand
What a 7.5 inch 5.56 actually does
- A 7.5 inch barrel is genuinely compact: the whole pistol is shorter than most rifle barrels on their own
- 5.56 out of 7.5 inches loses a great deal of velocity against a 16 inch barrel, typically 600 to 800 feet per second, so treat it as a close-range tool
- Muzzle blast and flash are substantial, which is the honest cost of the short barrel and the reason most owners fit a muzzle device
- It handles superbly in vehicles, in tight spaces and slung under a coat, which is the whole point
- Standard AR-15 magazines, standard controls and a standard trigger group, so anything you already own for an AR works here
Radical Firearms FP75556M47RPR specifications
- Model: FP75556M47RPR
- Caliber: 5.56x45mm NATO
- Capacity: 30+1, standard AR-15 magazines
- Barrel: 7.50 inches, steel, black Melonite, threaded
- Handguard: M-LOK RPR
- Receiver: black anodized aluminum with a Picatinny rail
- Grip: black polymer
- Buffer tube: pistol tube, no brace or stock fitted
- Hand: right
- UPC: 816903022366
It ships with a bare pistol tube: what that means
This is the single most important thing to understand about the Radical Firearms RPR 5.56 before you order. The Radical Firearms RPR 5.56 arrives with a plain pistol buffer tube and nothing on the back of it. There is no brace and no stock. That is deliberate and it is why the price is what it is.
If you want a brace, an SB Tactical SBA5 five-position adjustable brace is the usual choice and we keep it deep. Braces are sized for mil-spec carbine receiver extensions, so measure your tube or call us before ordering, because pistol tubes vary in diameter between manufacturers.
If you would rather not deal with any of that, the same 7.5 inch Radical pistol with an MFT brace already fitted is on our shelf and is the simpler purchase.
A word on stocks. Fitting an actual shoulder stock to a pistol with a 7.5 inch barrel creates a short-barreled rifle under the National Firearms Act, which requires ATF approval, a tax stamp and paperwork before the parts go together. MAG5 Firearms does not sell NFA items and we are not able to advise you on the process beyond that — a dealer who handles NFA transfers can. A brace is not a stock, and that distinction has moved around legally in recent years, so check the current position before you buy.
Magazines, ammunition and optics
Standard AR-15 magazines run in the Radical Firearms RPR 5.56. A Magpul PMAG M3 30-round is the obvious spare and we stock it in very large numbers. For ammunition, remember the short barrel: heavier bullets are not stabilized as well at reduced velocity, and 55 grain loads generally do better out of 7.5 inches than heavy match bullets do.
The Radical Firearms RPR 5.56 has a full-length Picatinny rail that takes any optic, and on a barrel this short a red dot makes far more sense than magnification. There are no iron sights fitted, so budget for a sighting system of some kind.
How it compares to the longer Radical builds
If the Radical Firearms RPR 5.56 is shorter than you need, the Radical Firearms 10.5 inch AR pistol recovers a useful amount of velocity while staying compact, and the Radical Firearms RPR 16 inch rifle is the full-length gun with none of the blast and none of the paperwork questions.
Why this firearm earns its place
- One of the least expensive routes into a quality-built AR pistol, from a maker that builds its own components
- M-LOK handguard and a full Picatinny rail, so accessories and optics need no adapters
- Standard AR-15 magazines and controls, so it shares everything with an AR you already own
- Threaded muzzle from the factory
- A bare tube keeps the price down and lets you choose your own brace rather than paying twice
This suits the builder who wants a compact 5.56 host and intends to finish it themselves, the shooter who already owns AR magazines and optics, and anyone who values a short package over downrange performance. It is not a precision rifle and 5.56 from 7.5 inches is a close-range proposition, which we would rather say than let you discover at the range.
Every firearm we ship goes to a licensed dealer in your state for the transfer and the background check. Call us if you need help finding a shop near you that accepts transfers.
Why the Radical Firearms RPR 5.56 handguard matters
The RPR in the Radical Firearms RPR 5.56 name is the handguard, and it is more of a feature than it sounds. It is a free-floating M-LOK tube, which means it attaches to the barrel nut and never touches the barrel itself. Nothing you hang on it, and no pressure from your support hand, puts a load on the barrel. On a budget AR that is the single biggest contributor to consistent groups, and plenty of pistols at this price still use a drop-in plastic handguard clamped around the barrel.
On the Radical Firearms RPR 5.56, M-LOK also means you bolt accessories straight to the slots rather than adding rail sections first. A light, a hand stop and a sling mount go on flat and light. The Radical Firearms RPR 5.56 handguard runs most of the length of the short barrel, so there is plenty of room to place things where you want them rather than where a two-inch rail section allows.
Radical Firearms manufactures its own barrels and handguards rather than assembling bought-in parts, which is the reason the company can sell a free-floated, M-LOK, Melonite-barreled pistol at this price at all. Background on the cartridge is collected on the 5.56x45mm NATO reference page.
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