And in case you think I was hiding a flyer:

Yep!

Now I need to find out if the vertical drift was me, the barrel heating, the gun or the ammo.

Have one myself, rsi/243, think it's just the mannlicher stock.

Haven't put mine on paper yet. Red pad .243.
Maybe next weekend if I'm not crippled (wasted 2 good days hobbled at home).

Somehow I have never owned an RSI, despite collecting #1's.

I'd probably try a few things first:

1. Quality handloads
2. Check the barrel for fouling/roughness. If needed fire lap it.
3. Relieve pressure points/inconsistent contact in teh barrel channel.

If that doesn't work, but you still like the rifle, I'd consider getting someone like Pac-Nor to rebarrel.

Finally got my ring/scope situation settled.

That is simply one of the most handsome rifles I have ever seen.
It is screaming in my ears: "Red Pad No. 1 Mannlicher"

1984?

I guess not so strangely, my 30/06 No.1 RSI likes the 150 grain blue box Federal.
http://i2.wp.com/www.classicsportingarms.com/wp-content/uploads/2010/11/lee-and-alex-005.jpg

I dunno the yr, will have to check serial #.
Most boring stock I've ever seen on a #1, same on other side.
I paid 650 for it, no rings.
Not a steal, has minor marks. It's a huntin' gun. Add more.
So whatever happens over time to the stock........aint gonna bother me.
Wish it had some kinda figure though. Yeeesh.
Pretty horrible IMHO.

Checked my serial number......1985.