The SPR rifle is more like a design concept rather than a specific profile.
The whole idea is to build the upper for specific tasks.
The only thing that most SPR barrels share in common are the diameter under the handguards and the use of multiple gas block seats for the ability to choose a gas system length appropriate to the barrel length, and still choose a different handguard length and front sight location. In many ways, the Bushmaster Dissipater is really an SPR design.
The SPR profiles can be used to build many configurations of handguard length, gas system and front sight location.
This barrel profile is available in all calibers that we chamber.
This barrel profile can be made to any length.