Slugs and FX barrels

I guess they are all different. My experience with an Impact MK2 and a 700 mm slug liner is that it likes the NSA 24.8 in .218. Once I started lubing them with Balistol the great groups got even better. I’m having the same experience with a Crown MK2 with a superior liner. This Crown MK2 absolutely loves the NSA 24.8 .218” also lubed with Balistol. The Crown also really likes the 27.5 NSA in .218 (also lubed). I went with the 24.8 grain because the precision was a little better and the higher velocity gave better expansion with that slug.
I did test .217 in both rifles and in both cases the .218 came out on top. The Crown delivers groups like these at 50 yards over and over again. 
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My Dreamline .177 cal doesn't like slugs at all. The choke is too tight and it leads up quickly. I have two barrels, a 300 mm and a 500 mm. Both are supposed to be "superior" barrels, but they don't work well with slugs. Hey FX, when are you going to change this??
You might want to try the 13.43 Knockouts and the 16 Zan slugs.
 
My experience is that each brand has slight difference in measurement indication. For example it could well be that you shoot NSA .217 perfectly well and then .218 from Javelin also whilst the .217 from Javelin shoots crap. This is just an example but counts for all brands and weight within brands. It is a matter of trial and error and not a case of “my barrel likes .217 or .216 or .218“ as a rule. But once you found a brand , weight and size that you like you can buy a truckload as the consistency is there by my experience this far in all renowned brands .