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Very possible that they are the same length. Take a fired 38-55 case and flare the mouth a bit and then chamber it in your 375. That should tell you if the longer 38-55 case will work in your 375. Then slug the bore to see how close it is to the 38-55 bore size. My 38-55 has a .379 bore and my 375 has a .376 bore. I have never tried 38-55 ammo in my 375. I shoot .380 cast in the 38-55 and don't think I will get good accuracy if squeeze them down to .377 in my 375. Your may be different.
