Hi Marc, the ATI Omni Hybrid Maxx has Mil-spec sized M4 buttstock and buffer tube. tactical-life.com/firearms/review-american-tactical-omni-hybrid/

what is mil-spec while it has a Mil-spec sized M4 buttstock and buffer tube no true Mil-spec rifle has a hybrid metal-reinforced polymer upper and lower receiver key word POLYMER

Marc, the ATI Omni Hybrid Maxx has Mil-spec sized M4 buttstock and buffer tube. tactical-life.com/firearms/review-american-tactical-omni-hybrid/

no it is not mil-spec it has a hybrid metal-reinforced polymer upper and lower receiver The ATI Omni Maxx P3 Hybrid is an AR-15 semi automatic rifle with hybrid metal-reinforced polymer upper and lower receiver. The hammer, trigger and lower parts are made of advanced self-lubricating composite materials. This modern sporting rifle has a 16" barrel and a polymer collapsible stock. The gas block rail is on the same plane as the receiver for ease in mounting sights (not included).
Specifications and Features
ATI ATIGOMX556P3
5.56 NATO (also accepts .223 Remington)
Gas operated semi automatic
16" barrel
1:7" twist
30 rounds capacity
Hybrid polymer upper and lower receiver
Self-lubricating composite hammer, trigger and lower parts
Collapsible polymer stock
Overall length 35"
Weight 5.7 lbs
Black