Is Over-polishing a barrel a thing?

Yes you can but I think that would take a really long time? Am I wrong on this? Don't take this as advice I'm seriously asking not telling. I've only polished 3 barrels but it seems like that would be more of an issue with lapping than polishing. I'm using a bore mop and a metal polishing compound and finishing up with jb bore bright. 
 
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You should push the slugs that are grouping best through by hand with a rod breach to muzzle. Inspect by eye & more importantly feel. Feeling for loose & tight spots, marking rod where you feel any potential tighter spots.

I don't know if it's choked, what OD slugs you're using, and harmonics are huge. Probably more important so research the polishing/lapping procedures and everything else.
 
Hi Pistonjohn,

It sounds like you have accomplished what you were trying to do, looks like it's a good time to stop. Overpolishig is definitely a thing. I have managed to accomplish this, and it didn't take nearly as long as you would think using flitz aluminum polishing compound on a bronze bristle brush I'm pretty sure its not nearly as abrasive as jb vs a 2009 challenger loather barrel with between mild-moderate rust. When the rust was gone and polished, there was about 35 ftp gone also on a slow moving projectile. 
 
If it is actually possible to over polish a barrel using JB products I would really like to hear about it. After what I did to one of my barrels, that I was planning on throwing away, I can't imagine how much time and effort it would take to actually ruin one. I am not recommending anyone do what I am about to spell out here, but just putting it out for general info. When I first looked down the barrel of my .25 Benjamin Marauder I could not believe how bad the machining looked. The chattering was evident and the choke tight and long. It was the first pcp barrel that I have seen that just looked bad. My Turkish, Chinese and German(of course) all looked good, comparitively. After cleaning it and pushing a pellet through I figured to throw it out and get a TJ's. So at this point I figured that I might as well experiment. I clamped it down with quick grips over a bench, so that I could get at it from both sides. Using a cleaning rod in a drill, with a long jag, with strips of rag covered in JB, I ran down the barrel from both sides for ten minutes each so that I would purposely hit both sides of the lands. Then I did ten minutes by hand following the rifling to get the bottom of the groves. Then I repeated the whole process using JB bore bright. I favored the muzzle by not putting the jag so much out the front as the rest of the bore. Then I ran patches until cleaned out and oiled it with mp5 then ran patches again. Between fiddling with everything, it took about 2 hours to do this. To do the amount of polishing that I did with the drill, by hand, would have taken all day. I pushed a pellet through smoothly and the choke was still, what I believe to be, too tight, but the markings looked good. So I decided to try it out. I never got the TJ barrel. Anybody can have an opinion, but I got a result. I am sure that there are abrasives out there that will take out your barrel. Don't use those, stick to JB products and you should be fine.
 
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400 to 600 grit finishes have been stated many times by educated barrel reworkers as ideal for air gun pellets / soft lead.

All one needs to really FEEL a barrel is with a hard rod and round jag tip with a dry snug patch is push a few from both ends and take note the friction difference.

Most barrels will indeed exhibit a near shark skin bias for direction and this should be smoothed out via some lapping compound more aggressive than a polish.



Been there, still do & will continue too ....



JMO tho and if unsure DON'T leaving it to someone more experienced.
 
It will require a person far more determined than I to ruin a barrel with J-B. As in hours spent scrubbing and replacing patches and replenishing J-B.

I don't want to put words in Scott's mouth but I think what he's getting at is J-B is too fine to do any form of surface leveling. The particles will shine the surface but not remove striations or other characteristics you might observe with a 5x - 10x loupe. However it will remove microscopic surface fretting that contributes to lead buildup, especially in the inside corners of the rifling (or in the choke, if present).
 
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To quote myself from a similar post on barrels just a few days ago ..... Personally find JB similar to using toothpaste to polish a coin, sure it shines but surface texture & grain structure remains unchanged.



Scott S

Thanks Scott,

I'll take that as meaning no, not likely to do any damage with JB. You gotta remember, some of us need your comments dumbed down to our level. Thanks,

Ed