M4 Cuts?

[WSAR15]

I just bought a PSA Light 18" 6.5 Grendel upper - it is nice and I like it!
The barrel extension has the M4 cuts but not the receiver. I know this may work (based on 223) but why leave the cuts out of the receiver?
Do your uppers have this characteristic?

[A5BLASTER]

No all my uppers have the m4 cuts but none of them are from psa.

My be one of the ways psa saves money and offers their gear so cheap compared to other company's products.

[LRRPF52]

Got any pics of this?

The Grendel really does well with M4 feed ramps.

I personally think it does better with larger feed ramps.

I've seen guns that were mist-matched like that, and it's harder on the shoulder, and can cause FTFeed.

Bill A. made some comments long ago that said basically the same, if I recall correctly.

Some 7.62x39 uppers have enlarged or even single feed ramps. Since we have a smaller diameter projectile, we get reliable feeding with M4 ramps on the Barrel Extension and upper.

[WSAR15]

My apologies, under better light the receiver is machined. My mistake.