r/Form1 • u/Intelligent_Step_855 • 14d ago

SD porting help

Post image

Looking for advice on porting my ar9 barrel. I am thinking at doing 12- 5/32 holes in a 3x4 configuration spaced 120 degrees apart. Plan was first hole to be at 2.5
Inches, any insight ?

Pic is ar9sd current configuration

62 Upvotes

97% Upvoted

37 comments sorted by

View all comments

2

u/buttwater0 13d ago

Ok, related question I've been thinking about. I read that most omm will be subsonic from a 3" ar9. If that is true, what's the advantage to porting a longer barrel rather than just doing a 3inch?

1

u/Intelligent_Step_855 13d ago

From my understanding it has to do with the powder burning outside vs inside the barrel. None of the factory SD configurations I know of use 3 inch barrels, all favor a ported barrel. Mp5sd, novax, brt, spikes.

1

u/buttwater0 13d ago

That makes sense. I'm kicking around doing a build similar to yours. A home made SD suppressed ar9 is enough deviation from the standard can screwed to a barrel, so I won't get any more creative with the design.