I have some .348" 225 grain swaged lead boolits for paper patching to use in my .358 Win. I patched one that came out .364" and started to make a dummy round for functioning through action.
I measured the inside neck of a fired round and found it to be .360"....hummmm. Instead of resizing the case I just used it as fired, just to see. The outside of the neck with the boolit seated is .389" and the fired case is the same. It chambered easily but had a very light scuffed ring 1/3 of the neck down. So my question(after being so long-winded), do I have enough clearance for the neck to expand to release the boolit safely? I don't want any rapid disassembly to my M.70.

Yes, you are OK as far as pressure is concerned, assuming a cast boolit load in the first place. However, you might find the accuracy will improve with turning the necks of those cases, at least just enough to show no more magic marker scraping. ... felix

The thing to ensure is that there is SOME clearance for the neck to expand. If it can't expand, the pressures go up fast.

How much is SOME? For my benchrest 6mmPPC with turned necks I've heard (therefore take it with a grain of salt) that 1/1000 on the diameter is minimal with 1/1000 clearance on each side is good.

How much dirt and crud will the neck of the chamber accumulate? That's the issue. That's why machinegun chambers are so large - where function is more important that precision location of the bullet with the axis of the bore.

The fired case fitting easily into the chamber is a good rule of thumb. A little more clearance is safer. A tight fitting case (around the neck) is obviously the wrong option.