You might look into getting a very plain 7/8" barrel, 16" or 18" long. Something like the most simple, basic Palmers brass barrel, or a standard birdcage tipped Armson barrel - one with a consistent outer diameter and no porting.
You can then build a sleeve (a mock barrel) from PVC that extends beyond the muzzle of the true barrel by 10"-12", and mount a muzzle brake to that. Drill and tap four holes at the base of the sleeve and four where the tip of the true barrel ends, and you can attach and remove it with set screws for cleaning or travel.
I would go with 16"-18" but no more or no less - longer and you'll have trouble with velocity and have additional risk of paint shreddage, shorter and you'll risk your PVC not having enough support and drooping, or paint potentially hitting it when exiting the true inner barrel. I would also consider making the ID of the muzzle brake larger than that of the faux outer barrel. With a 18" inner barrel barrel, you could sport a 28" mock outer barrel, and 4" of muzzle brake - that's 30" total.
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Last edited by Frizzle Fry : 12-07-2013 at 06:55 PM.