Turns out I have only one pic of my GRRW, and that's the butt stock only. Camera is off to Nikon for repair, so it will be a while for more. Here 'tis:
I've been in contact with the GRRW gunsmith who built my particular rifle. Here's what he had to say about them:
"I can tell you that the secret to the accurate barrel is the way they were bored and rifled.
They were first drilled as usual. But what is unusual is that they were never reamed as most if not all barrel makers do now - and did then. We first cut the lands and then cut the grooves depending on the bore size. It's been a long time but as I recall the big bores had the grooves cut first. This made for tool marks that ran the whole length of the barrel on both lands and grooves in the direction of the bullet travel. Also, as the cutter head advanced towards the muzzle oil pressure and some cuttings put a minute amount of pressure on the cutter and you ended up with a sort of choke near the muzzle. This was accidental and was discovered while "slugging" a barrel to check for rough spots. Once found on a test barrel we noted it on all of them and theorized the above means by which it occurred. The result was a barrel that needed just about zero break in and was wonderfully accurate as you have discovered. To the best of my knowledge no one is producing barrels in this manner. So you have a real prize there...."