I have one, an 1980 year made marlin 375. I have been shooting cast with it using fire formed 30-30 brass. Brass and ammo both are hard to find for the 375. I've got a few feelers out for brass now. It appears that Winchester only makes one run of brass per year.
I would be leery of going beyond a medium load using 38-55 or fire formed 30-30 brass as both will be thinner brass than original 375 Win brass. The 375 is designed to operate under much higher pressures than the 38-55 and of course the 30-30.
I've only had my 375 a few weeks but I have found it to be very accurate. I have only shot it with open sights and with my old eyes, I can group 1" at 50 yds. Once I scope it, I'll extend my target range. Right now, the front sight is just to fuzzy for me to get past the 50 yd targets.
Once I find some new brass which I will, I'll up my loads. I see some online stores are expecting brass in February.
Since I cast my own bullets and have two molds for this caliber and since I reload, ammo will not be a problem.
I wanted to add to my post. For those of you wanting to use 38-55 ammo, my recommendation is, Don't Do It. The 38-55 bullet is .377" diameter while the 375 is .375" diameter. The 38-55 brass is about .060" longer than 375 brass. This is a problem looking for a place to happen. I read some people do it and get away with it but I wouldn't try it.
Using 38-55 brass is OK as long as it is trimmed to correct length and the loads kept mild. 375 brass is thicker to handle the higher pressures.
Just my .02
Sam
Last edited by Down_South; 12/16/12.
