My Mk 4 has only moved on extemely cold days, think fro memory it was about -5, a winter league shoot and every one was struggling.
In the recent Shires 100 where Rob I think first experienced the March shifting due to heat, I had no problems with the mk 4 and that I have to say I was impressed with as it was easily the hottest days (30?) shooting i have used it over the last 3+ years.
BFTA Grading Q's to; firstname.lastname@example.org
sorry wont answer Bfta q's on forums, Cant keep track of replies etc!
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REV26 Ostler Ev2 & x45 comp awaiting a Gary Cane Stock!
Beast Priest Ostler
Ev2 & x45 prem ret comp in Warren Edwards stock
If you want the best, Ostler is the man
Pump your Fish, Little or Large
MFTA visitors World championship - Arms dealer 97, Awesime 94, Acid Hands 85