The 375 Improved, like other improved belted cartridges, is not a good one due to the short case life.



On mine the throat is so far forward that even when long bullets are seated backwards the heel of the bullet cannot reach the throat. The only bullet that will reach so far is the 285 gr Speer and I am about out of those.



So I have been firing full power .375 H&H factory loads and then throwing the cases out after two or so reloads.



What I had thought of but not done yet is to make brass out of 416 RM's. That way I should be able to set the headspace on the shoulder right off.



If I knew in 1970 what I know now I would have just got a standard .375 H&H and if a more powerful cartridge were wanted then a 458 or maybe a 416 RM.



Another fix for my rifle would be to have the barrel cut back so that a standard unfired 375 H&H headspaces on it's shoulder like a rimless improved case does. This would cut the case capacity back which is not that bad a thing anyway but would require a neck reamer too. On top of that I had the smith taper the barrel over the chamber to match the M70 taper. There may be enough meat to do it though.



Another answer, now that you have me thinking about it, is to take the gun for a walk down gun show lane.



As of now I am going to do nothing. I don't use it anyway and don't need the space.

This works awesome,



I use a .375 JRS Which is simply a .416 rem mag necked down. All you have to do is Full length resize them, and away you go.You also can use 8 rem mag brass but you have to do it in two steps.

What I do for my .375-.358STA (which is close to the .375 IMP) is neck Winchester .375 H&H cases up to .416 and then run your die (.375 IMP.) down until the bolt will just barely close on a empty case. You can order a .416 tapered expander ball for most all dies if you dont have a set of .416 dies. You only need to run the cases in until the neck is opened. Basically what is does is create a false shoulder to set the headspace. Then I use a load that is about 2grs under max for a .375 H&H using 200 or 220gr flat points. I've lost maybe 1 or 2 cases out of the 300 or so that I've formed.