LW polygon barrels

Here is my advice on barrels, and it's worth what you are paying! Get the barrel clean, really clean, properly using a rod and nylon brush, then polish with JB paste. My limited experience with poly barrels suggests that pull-through cleaning is not going to be sufficient. If you have access to a bore scope, now would be a good time to take a look. If the barrel doesn't shoot within the next 100 or so pellets, it probably never will, and it probably has a machining error somewhere. Send it back, or just buy a new barrel. Life is too short to fuss with a bad barrel. And if I were replacing the barrel, I would go with a traditional cut or button rifled barrel. The barrels on standard production rifles are always a crap shoot. Some are very good, a few are very bad, and the rest are somewhere in between. 
 
Hi @elh0102, thanks for your advice! Here's a quick update after a good cleaning. (no JB Paste yet) I definitely think this barrel show potential. Here are 5 10-shot groups at 62 yards. The top 3 were essentially shot during a period of dead-calm. The bottom two were affected by wind. I did finally get around to ordering a Patchworm kit. We'll see if that's able to pull out any fresh gunk from the barrel 👍

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Nothing wrong with those groups at 62 yards

Thanks @Motorhead. FWIW, the gun developed a leak at the firing valve and being under warranty I shipped it to AoA. They fixed the leak and replaced the barrel. As you saw above the original barrel did perform well but required cleaning about every other fill. When cleaned I pulled out very large slivers of lead buildup. The new barrel is just as good but goes much longer in between cleanings.

I posted about it here: https://www.airgunnation.com/topic/question-for-brocock-bantam-owners/

And my main thread on the gun: https://www.airgunnation.com/topic/brocock-sniper-hp-in-the-house/page/3/

Both this and the original barrel shoot the .22 Monster Redesigned well on high and (ironically) CPHP well on low. How's that for an odd combination? It still hates most other JSBs. I do like the fact that when I clean the new barrel I get very little lead flakes out. It's nothing like the 1st barrel in this regard!