FNH USA introducing Tactical Box Magazine upgrade for SPR rifles

FNH USA is introducing a new upgrade for their Special Police Rifle (SPR) that allows it to use high-capacity magazines. This Tactical Box Magazine (TBM) conversion kit allows you to swap out the existing magazine well and trigger guard that accepts extended magazines.

The TBM conversion kit increases the capacity of the SPR from 4+1 to 10+1, and FNH USA includes on 10-round and one flush-fitting 5-round magazine with it. This upgrade essentially adds the same magazine system used in the SPR A5 to the A1 and A1a models (the A3G, which uses a different-style stock, requires modification). From the press release:

“We are pleased to offer this new TBM Conversion Kit,” said Ken Pfau, FNH USA Senior Vice President for Law Enforcement and Commercial Sales. “It was developed specifically for owners of the original SPR, which came with 4-round Detachable Box Magazines (DBMs). The ‘drop-in’ capability of this kit not only takes the guesswork out of performing the upgrades themselves, but it also gives them an opportunity to economically upgrade their rifles to better meet their current shooting needs.”

According to FNH USA, the upgrade can be done in minutes with just simple hand tools. You may have to run out and pick up a torque wrench if you don’t already own one, but it’s an easy upgrade and breathes new life into previous model SPRs. And while not inexpensive—the conversion kit costs $400—it’s still cheaper to buy an A1 or A1a model and upgrade it than it is to buy an A5. 


The Special Police Rifle is everything a production precision rifle can be. It is currently in service with the FBI’s hostage rescue team and showcases what FNH USA can muster. Every SPR is guaranteed to shoot sub-MOA (minute of angle) and with good ammo will shoot under .5 MOA. They feature hand glass-bedded receivers, fluted free-floating chrome-lined barrels and McMillan stocks.

They’re patterned off the Winchester Model 70 short magnum action, have claw extractors and blade ejectors. A lot of attention to the controls has been paid, and they have adjustable triggers and knurled bolt handles for fast and easy operation. They also have 3-position safeties. Finally, they’re parkerized for a long-lasting and very durable finish. 

According to Tim Roberts of Crescent Customs, this upgrade is overdue but has adds excellent features. “The FN TBM kit, as a direct conversion with little to no fitting required, is a major plus for my customers. The magazines are extremely well made and the design of the follower makes feeding flawless. Its double stack design also makes for a very short 10-round magazine, which is a big plus for tactical competitors. In addition, the ambidextrous magazine release is a very nice feature to accommodate the left or right-handed shooter. Overall, this is a very nice conversion kit with a very affordable price tag.”

We have to agree. While it’s not a cheap part, if you’re looking to bring your older rifle up to speed, including some Remington Model 70 (which, like the A3, may require some modification) it’s a lot less expensive than having custom gunsmithing done. And it’s also a way to built a high-end target rifle bit by bit. You can get an A1 or A1a and upgrade it down the road. 

Photo credit phm14.

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