A client is very eager to build a .450 Rigby and asked my opinion of building one on a M70 Ultra Mag action. I advised against it, since most actions intended for Rigby sized cartridges have a larger diameter barrel shank and bolt body. Then, I remembered Dakota offered the .416 Rigby in their M76 action which is just a M70 variant. So, am I being too cautious or would the M70 action be OK for the .450 Rigby?

Also, since the Ultra Mag cartridges are nominally 3.6", the length of the M70 magazine box, would it be safe to lengthen the mag. well for a cartridge that is .150" longer?

Thanks,

Roger

CZ550. Built mine on this action. Very easy to make feed properly. M70 just is not large enough.

Same action Rigby uses for the 450.

Mine below when I was in the building process.







This cartridge with full loads has "generous" recoil. I used a no. 6 barrel with 1.300" breech diameter. Competed rifle weighs around 12 pounds.

Woodhunter: Thank you for your post. I completely agree about the CZ 550. They are a fine action of the correct size and respond very nicely to custom gunsmithing.

Roger

I'm no gunsmith but wouldn't one of the Ruger RSM actions work? I have one of the first generation RSM's, with the heavy barrel, in 416 Rigby and thought it could be rebored to 450 Rigby.

Just to confirm, I have a Dakota M76 in 450 Rigby; functions fine but buffalo hate it.

recall this is the 416 rigby case, which is HUGE/

m70 would be a 1 down 1 up affair, if you could get it to fit, that's the only way it would feed most of the time.

start with a cz550 in 458 win or lott, get the rigby follower and open the bolt face before rechambering

quote:

Originally posted by Labman:
I'm no gunsmith but wouldn't one of the Ruger RSM actions work? I have one of the first generation RSM's, with the heavy barrel, in 416 Rigby and thought it could be rebored to 450 Rigby.

Dave did that with, i think the first, 470mbogo

I have built many on the CZ 550 and BRNO ZKK 602 and am doing two currently. The Win 70 does not have enough room and it would be a nightmare to try to get it to work. Best approach with the CZ/BRNO is to start with a 416 Rigby action or donor rifle. The bolt face is correct as is the follower and mag box. It's not difficult if you begin with the right action.

Woodhunter, could you tell me the name of the book in the pictures please?

Jim