Sionics Weapon Systems has released their SPR barrels for purchase separately or assembled in limited production upper receiver groups. These are the same barrels that they designed for the Matt Axelson tribute rifle project that Sionics was a part of and it shoots very well by all accounts.
These 416R stainless barrels are 18″ in length. They have a 1 in 8″ twist, .223 Wylde chamber, rifle length gas system, and M4 barrel extension. The profile is a slightly heavy, SPR type profile. The barrel ships with a gas block and is dimpled to make installation easy.
Sionics is offering three uppers featuring this barrel. The main difference between them is the hand guard. There are two Geissele SMR options and a 15″ Samson Evo option. Each upper includes their excellent NP3 coated bolt carrier group. Considering that these uppers feature a great barrel and come with a bolt carrier group, it is hard to beat their pricing.
If you have been shopping for a precision AR-15 upper, act fast.