G'day Tas...
Firstly, sorry but i havnt read the entire thread...
I havnt done much walking the woods as compared to many of you other blokes...but have done a bit...
In more recent years ive tried the duct tape over barrel practice.
Not only for the walk-about routine, but also & mostly because the most shooting i do is at night from the car with a spotlight; & i rest my rifles muzzle down on passanger seat, which causes some scratching on the end of barrels... (actually the end of the barrel of my old brno 22 looks a highly polished steel ring surrounded by old 70's gun blue at the muzzle from this...i rekon im going to start a new muzzle look trend...
)
Ive made a point of looking at the tape after shots & have often noticed the tape appears to have been blown off from pressure within the barrel .
Ive had to google the 'hydro lock' you mention, & i dont think a small peoce of duct tape will ever be able to cause grief in the form of hydro lock from stopping air infront of a bullet blowing out a barrel at 40 plus thousand psi of pressure...granted the pressure at the muzzle prob wont be the same as at the chamber, but still, the average car tyre is running 32 psi & duct tape wont fix a tear in the side wall.
Oil & other contaminents i wouldnt know & wouldnt risk it...
Personally, im a muzzle up guy...easier to manage the weight of rifle, easier to guide the barrel through shrubbery, less risk of suddenly slamming the crown into the ground or a rock when your feet disapear out from under you trying to work your way down that rocky or slippery slope...
Id rather my crown brush past heaps of sticks, than slam into the dirt once...
As for poi shift...are we all shooting animals, or are we shooting the rouge pubic hair poking out the forskin off a juvenile field mouse at 476 yds...?...
It wouldnt be hard to figure that out...a few groups into paper with & without tape over muzzle will give the answer, & ive not noticed a difference on fur in the field...
(Got my first Fallow this morning...YAY...!!!)
The man who knows everything, doesnt really know everything...he's just stopped learning...