Can a bb affect the barrel

Since I plan to get a JG BAR 10 I would like to know what kind of bbs to use. With my AEG I could only use high polished bbs. Does this apply to the sniper? Not that I would use 12g bbs in a game but if I just want to shoot outside. And could a 12g bb affect my barrel in a negative way (scratch) over time.

I'm going to be frank (you can be bob if you want).
.12's are no good in any gun.

.12's with seams will tear at your hopup and will seriously scratch the barrel (especially if it is tight bore).

So I'm going to say...yes, it applies to sniper replicas as well as AEG's.
If you have any .12's, sell them or use them in M03 moscarts...theres no other use for them.

AND...

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I agree completely, .12g BBs are for entry-level plinking guns and for grenades. I wouldn't use anything but .12g BBs in my 40mm MOSCART shells. .20g BBs should be your minimum for your airsoft guns, whether they're shotguns, pistols, AEGs, or sniper rifles. .25 is preferable for more accuracy. I'm stepping up to .28 in my AEG soon. So quality is a must, and the heavier the better. I'm a strong proponent of the G&G biodegradable BBs.