We tried and tried to get a standard extended mag box to work and ended up going with the center feed mag box. I have to drop my floor plate and feed the mag box from the bottom but it feeds like glass, very smooth. Yes, your action you described will work fine. If you are interested I would sell you my reamer and go gauge for 100.00 US and I would also be willing to send Hornady a fired case of mine and they will make a set of full length dies for a 140.00 which would save you a bunch over the RCBS customs. I had to buy the RCBS custom 450 Ultra dies because I had no fired case to have Hornady go off of. Let me know if I can help you with your build in any other way. It is a TRUE power house cartridge and very manageable in the recoil department with the muzzle brake.
Hi Smack, I am a big fan of your 450 Ultra and looking to get one done. Was hoping you might be able to offer some advice regards it? I am looking to start with a rem700 SPS and use wyatts detach mag system- eg the 8-10 shot mags for the RUM cartridges. Do you think this could be made to feed as well as well as the wyatts fixed system you have? I am in australia also so will have to buy a reamer from PTG(I think?) and wondered also about dies. I see some being sold on midway/RCBS shop memory called 450 Ultra dies and wondered if that is yours or another version? . I have access to barrels etc and good gunsmiths so as long as I can get the theory sorted out and the right parts I am hoping it should work out okay. Thanks for any advice regards the above.