Hi all, I would appreciate your thoughts on what is involved in converting a Ruger M77 MkII Magnum to 510 Gibbs. I say 510 Gibbs because the rifle in question is already a 500 A Square.

Thanks in advance.

Lucs

"We were expecting you."
Come right this way, have a seat, this won't hurt a bit.
Send that thing to John Ricks with instructions to chamber it for a 3 3/4" 510 Cayenne Express.
It's a simple conversion. It's the Gibbs with .15" trimmed off that mile-long neck. Turn back the barrel a bit, rechamber, open the boltface, widen the rails a bit, shoot, drink beer, go to sleep.
You'll be about 8g of water behind the Gibbs, and about 32g ahead of the A-Square. Same COL as A-Square.

I was thinking of doin' the work myself. I also really am not too interested in shooting a wildcat. I don't think anyone will notice that my "505" Gibbs is shooting 510 bullets. If someone loads a proper 505 Gibbs round in the rifle, no big deal really. Velocity will be down and accuracy will most likely be off.

Do you have contact information for Mr. Ricks? Would I be correct in assuming from your post that Mr. Ricks is experienced in these kinds of conversions?

You can PM him off of here easy enough. Just find one of his posts. Or search here or Big Bore for his name, then go to his profile and send private message.
As for his experience, I can't say. He says he's working on a 408 Chey-Tac, which is Gibbs-based, and he claims to have lots of big machines that go "whirrrr" and "vussha, vussha" and other sounds. There are at least a few folks here who recommend him for big-bore rifle work. I mentioned his name for a few reasons. He's working on the 408, he'll split the cost of a reamer with you (and keep it), and he's a gentleman in the line of fire, as witness by me during the barrage of questions I assaulted him with while he was helping me sort out what I wanted from him.
Here's his webpage:
http://home.earthlink.net/~rifles/

You're going to have to open the action another tenth of an inch or more, not sure if that's front or back. If you're doing the work yourself, I assume you already have way more experience than I do.
But I hate to tell you, it'll be a wildcat.
You're not going to chamber for a 505 Gibbs and then load it with .51" bullets, because they won't fit into the neck portion of the chamber.
Not unless you knock off .005 from the neck, which would leave you with a bout .0095" neck wall. A bit thin. Otherwise, you'll have a match neck, unsuitable for hairy situations.
Clymer's reamer is .536" at the mouth. That leaves .026" after bullet, divided into two giving .013", which is about perfect for a tight neck on standard brass.
So you'll need a custom reamer, and custom dies to size and seat. That, my friend is a wildcat.
Which means, you're free to do exactly what you want to do.
Think about it.

It wouldn't hurt to check with Hamilton Bowen. He regularly converts Rugers in .416 to .505, and who knows, he just might already have a .51 Gibbs reamer.