You have to be careful with inner barrels and especially tight bores. The tighter the bore, the less accurate a barrel will be. On the other hand, a tighter bore gives you more power, so it allows you to use a weaker spring to achieve the same power, alas, at the cost of accuracy.
The very low end (read: cheap) tight bore barrels are usually no better, and sometimes worse than stock inner barrels. You absolutely need to buy from a reputed brand. For a JG sniper rifle, if you didn't change the hop-up unit (that is a good thing, it doesn't need to be changed, just shimmed properly) you need a barrel with a VSR cut, look for PSS10 barrels from Laylax or if you have a lot of spare cash, the PDI barrels are slightly better, but twice as expensive.
If for some reason you did change the hop-up unit, most replacement units use AEG cut barrels. You have a wide choice of barrels, but again, the Laylax/Prometheus barrels are the best bang for the buck, the PDI are a bit better but much more expensive.
If you are going to change your inner barrel, don't cheap out, a low end barrel will not give you much more accuracy than a stock barrel, it's a waste of money.
As for how tight of a bore you want, for a sniper rifle don't go smaller than 6.03, the Laylax/Prometheus 6.03 are great, but the PDI 6.04 and 6.05 are pretty amazing too (but are expensive...).
Edgi barrels are very hard to find in Canada, and I'm not sure Edgi still makes them, haven't read or seen anything new from him in years. They were good barrels in their time, but quite expensive and made of brass. Good stainless steel barrels such as Laylax/Prometheus/PDI will perform better.
Keep quiet. Sound travels faster than BBs.
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