Is Too much up pressure possible?

[jonh172]

Well I figured out why my rounds were dropping off...

The front scope caps screws were backing off!!!!
I was even able to duplicate the issue After re-torquing the screws.

I picked up some new rings, torqued it all down and went back to work.

With a fairly hot barrel I put up these groups.

Imgur: The magic of the Internet

3 shot group at 112y, hot barrel, Federal 180gr.
5 shot group at 112y, hot barrel, 2013 Canadian MK8Z ammunition.

I bought some Hornady 174gr fmj/bt to try out some handloads.
We shall see!

[Bruce_in_Oz]

As for "zeroing":

When I learned to shoot No1 Mk lll rifles courtesy of the RAAF, there was a specific "drill" on the range:

"Two "warming" shots into the backstop, SOMETIMES two "sighters" onto the target, then shoot to score. This, of course, after previously having the rifle zeroed weeks or months before.

When it comes to hunting rifles, i suspect the game is not going to loiter about whilst you warm up your barrel.

This is why rifles used for deer-stalking or similar pursuits, need to be "cold" zeroed, with ONE specific ammo brew. This is, of course, time consuming, but it will seriously improve your chances of a one-shot field-shopping trip.

If you are doing serious pest destruction / feral extermination, less "subtlety" and a "hot" zero may work better. How many rounds and at what rate of fire, does it take for the zero to "walk"?

If hosing down hordes of feral pigs whilst you are hanging out the side of a helicopter, the movement through the air may well cool one side of the rifle more than the other. Things start to "deflect" when this happens. Plenty of interesting videos on that activity on the Intertubes, Lots from Texas.

One of the things about a properly-stocked original No1 Mk111 is that the barrel, being confined inside an insulating wooden shell and mechanically pre-loaded to be tuned for the ammo, will deliver quite consistent results through several "rapid' strings on a range, be it target or "two-way" type.

Strip away a lot of that insulation and "tricky" bedding and things WILL change, not necessarily for the better. Change the loading or worse still, the actual calibre / barrel, and it's serious challenge time.