What is the best procedure for opening up a Model 70 long action for a 450 Ackley? The mag box is 3.600 on my pre-64 Mod 70 action and I'd like to be able to open the action up enough to fit the full sized cartridge 3.650. Can I get away with just opening up the rear of the action and not touch the ramp? The bottom of the ramp and bottom locking lug don't have much metal there at all. The sheet metal mag box is of course no problem. My Ph in Africa had from the Win custom shop that used the stock box and he had to load his bullets deeper in the case. I'd like to avoid that. Who out there has done this and how did it work out.-Rob

Hi Rob. My 450 Ackley is built on an Enfield action, so I haven't tried it on a 70. I've been looking at one of mine though, and it looks to me that you can gain most of your length from the rear of the action. I'd be interested in hearing from someone who has actually done this as well, though. - Dan

As an after thought, if the original 70 was chambered for 375 H & H cases, there really shouldn't be very much needed to make it fit. Some feed rail mods for feeding, but the cartridges are the same length. - Dan

Dan- The action will just fit a 3.600 cartridge like the 300 H&H or 375H&H. The 450 Ackley is a .060 longer cartridge so the action will have to be opened up about .100 to fit. I think it can be done from the rear (which looks best to me) but I'd like to hear from someone who has successfully done it before I start milling!-Rob

I think .100 is as far as you can go before you run into the center guard screw hole but to that point it should be OK. Regards, Bill.