You should be able to leave the rear bridge holes as-is. I recently had a 1990's era Model 70 .338WM built into a .300H+H. Besides barrel, the action work simply involved removing spacer from rear of magazine and changing bolt-stop/release. Also had to adjust follower to go to rear of action more. Easier seen than done.I have a bit of a quandary.Picked up a stripped 1950 model 70 receiver that was a .270 win originally .Want to put a .300 H+H barrel on it and have the action milled out to fit.This will eliminate the forward hole at the rear of the action.The .300 H+H two hole spacing at the back were .440" Getting a 2 piece base to fit may be fun.Would involve D+T one more hole at the rear.Warne makes a weaver style steel base .440".Don't want QD rings and was wondering if med steel rings were available in Leupold compatible with Weaver style base ? Anyone know if the Warne Maxima rings are alloy or steel. The web site wasn't much help.
Yes I realize, but you can do without it. I know what you mean as I also have an original model 70 (1954) .300 H+H. PM me with your email address and I can send you pics of both rifles bridges if you like. Another thing I just thought of is your action is a non-magnum. When I was looking to do my project I was adviced to start with a magnum due to extra cost.The original .300 H+H actions have the rear of the magazine well milled out and a notch in the front receiver with rear hole spacing .440" not like the other calibers.This when altering a .270 size would remove the typical front base hole on the rear receiver requiring the drilling of one additional hole to match the .440" measurement .I just want to make sure I can get a rear base to fit.