Barrel laping budget co2 and spring air guns with built in moderator.

Hey guys I just laped the barrel on an old gamo hornet I own and it improved the accuracy significantly. Now I would like to do the same with my gamo swarm and umarex fusion however both have a permanent silencer attached that I would rather leave intact. Does anyone know how to properly do that? I was thinking of removing the barrel and laping it breech side first and then spraying a whole bottle of brake cleaner down the barrel and moderator to remove the compound. Anyone have a better idea? Thanks
 
A method used to polish barrels for shooting cast bullets is to use a bore snake with chrome polish. The polish has very fine abrasive in it. Just coat the bore snake with the polish and pull through about a hundred times. Recoat bore snake every 10 pulls. Then flush with contact cleaner or bore scrubber. Try both solvents to see if they will disolve or soften the plastic before soaking it.

I have done this on several rifles and have had great success. 
 
I prefer fire-lapping as it takes less elbow grease, and it’s a good use for throwaway pellets.

I’ll cut off the end off a Q-tip and use it as a tool to dab a blob of fine polishing paste into The breech; load/fire 2 shots. Blob again and repeat. I’ll give the bore a wet patch clean every 10 shots and repeat the process for around 50 shots, total.

If u slugged your bore before starting, subsequent sluggings will feel smoother. Keep at it until ur satisfied with how polished the bore feels. The level of progress will depend on how rough the bore was when you started
 
All great ideas guys, i especially like the idea of the better cleaning solvent to protect the o-rings. Also I know fire lapping can have great results but the whole point for me is to learn how to properly lap barrels with a slight tapering of the barrel to add even more accuracy. Thats the way id like to go at least until I teach myself the skill. After that ill probably fire lap everything out of laziness alone😂. Thanks guys.