Fx carbon sleeve ‘gap’

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When fitting a fx carbon sleeve on my wc mk3 sniper, there’s a slight gap

ive used 2 of the o rings to fill this gap, but accuracy isn’t quite as good as without the carbon sleeve 

is there any other way around this ‘gap’?
 
Ok so I can happily use tape to get a very snug fit … but this still isn’t going to cure the problem of still having a small gap … ie the carbon sleeve doesn’t quite cover the whole barrel/liner

Its going to be shorter than the actual liner. Has to have room to fit the liner through the barrel connector and also have room for the liner lock nut.