Reply To: Barrel polishing by pellets

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nervoustrig
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Lead, even harder lead alloys with antimony, is vastly softer than steel and will do nothing to smooth out a rough bore or one with a restriction.  Of course a choke is a deliberate restriction and you don’t (usually) want to enlarge it.  And you won’t with J-B unless you make it your life’s mission.  In fact it’s too fine for some types of barrel smithing operations.  

So if all you need is to reduce the sort of fine surface fretting that tends to strip off lead from pellets as they ride through, give it a go with a good cleaning rod.  Work from the breech end to avoid scraping the cleaning rod against the crown, and give it 100 strokes, loading a fresh patch (or cleaning pellet) every 20 or so strokes.   Avoid exiting the muzzle.  Let the patch get right up to the end so you get all of the choke but don’t let it come out.  I clamp a stop in place.

I like to precede all this by pushing through a few pellets to get a feel for how much resistance there is when it’s in factory form.  Then after working it with  the polishing compound, I clean the bore well and push through a few pellets again to see if it has improved noticeably.

Just a quick anecdote, a couple of weeks ago I was working with a pre-release version of a new PCP.  After some baseline testing, I pulled the barrel to inspect it.  As expected of a budget model, the bore was pretty rough.  After a thorough deburr and polish, the velocity increased by 30fps (less friction) and accuracy substantially improved.  I never touched the HPA internals and the hammer spring tension was locked in.  All of it was from the polishing.