OK, newbie to this section,how do i score these

[remorem2jh@supanet.com]

HI all
Been shooting for a while now mostly hunting but got a new longer garden and trying for the best 5 shot group i can muster. Mostly shoot springers but got an s410 to 'cheat with' now and then.
Best i can do so far is with my .177 Webley Stingray with self fitted 'v'glide piston @32yds approx. 13mm total group or 5 shots including a .22 aim point this is measured edge to edge rather than ctc (although i don't really know the difference) how do i get an accurate reading?

[hwtyger]

You mean how to measure ctc?
Easy, subtract the calibre on yr edge egde measurement.
So for 5.5mm, 13mm e-e is 7.5 cc.