Sorry for the confusion. Ramping the
carrier makes the trigger recocking more gradual, its suppose to minimize the stress of the pins ( holes from egging out , pins from walking)
Ramping also allows the use of most "non" 9mm hammers
As you can see from pic below of a RRA carrier, a match hammer like the CMC gets caught in the notch as the bolt travels forward. This locks up everything so bad you need to drop both takedown / pivot pin out to free it up. Also you cans see trigger gets cocked after a very short amount of bolt travel
After ramping, the cocking is much more gradual . Notice the ramp is similar to a standard AR ( 223 ) carrier now.
You can feel the difference. With a unramped carrier, as you pull the carrier back, you can feel how quickly the hammer is cocked. With a ramped carrier, you need to pull the charging handle back further before hammer cocks
I use the RRA upper on two lowers. One with a CMC , other with a RRA NM trigger with no problems
Any decent machine shop can do this