Rifle Scopes Pica and mount: steel vs. alloy

Jayjay1

Gunny Sergeant
Full Member
Minuteman
Oct 30, 2018
933
484
Hey guys,
my go-to hunting rifle (a .308 Win.) has a steel picatinny rail and a premium steel mount.

No I´m building up a predator rifle, AR15 with an alloy upper receiver.
I have to safe some money to get me the optic and mount I want, so there´s a gap stop mounted right now, with a PEPR from burris, also alloy.

I can switch optics on my 308 (steel/steel) all day with no scope adjustments needed, if at all it maybe a 1/2" of at a 100yds.
But mostly I don´t see any difference.

A complete other story with the pica and the mount being out of alloy.
When I take my scope down and mount it again, I´m 4-5" at least off every time.
And not only that, the first 4 or 5 shots are building a "string", they seem to travel downwards on the disc.
So it seems, that the mount has to settle as well.

Can someone confirm this observation?

And my question would be, if I can fix this when I´m using a steel mount (as a first step for the upgrade) on the alloy pica of the upper receiver of the AR (which I can´t change)?
:unsure: