I want 18" and Rifle Gas,but am happy to drop contours. I've seen longer handguards protect fingers and assist in keeping muzzles pointed where they should be,in order to preclude sight height POA/POI close proximity woes. Hint.
As to turnbolt feed/function woes on shorter cases,I prefer to shim the front of the box(aluminum) and carve a preemptive feedramp into same,which is a funnel to the funnel. It keeps case heads at a friendlier ride height,in relation to the bolt's nose. Hint.
Montucky 6BR here. Hint.
Have the boys Krunchenticking,until it's time for a Custom Turnbolt. Hint............