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Old June 13, 2018, 07:59 AM   #1
NINEX19
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Join Date: December 12, 2001
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Marlin 375 winchester cast bullet information

Background info:
I have had a Marlin .375 Winchester lounging in the back of the safe for many, many years without being fired. The main reason is that it is virtually impossible to find any factory ammo or even just brass and bullets to reload with. Nobody makes brass and Speer is the only manufacturer of one bullet. The two online retailers I can find that sells Winchester factory ammo want @ $3 per round and then stupid prices to ship one or two boxes (@$75 for 20 rounds). I should have stocked up years ago when it was slightly more available... @1981. So, this is pretty much an obsolete caliber.

Question:
I recently discovered from my online research that 38-55 ammo, brass and bullets are readily available and are perfectly able to be shot in the Marlin .375. I now have brass, some .375 Speer bullets (200g), and a 250g Lee bullet mold in .379 diameter. I decided to try and cast for this rifle so I can have some cheaper fun. The bullets are coming out at .379 as advertised. Powder coating makes them come out to .380. There does not seem to be a .375 sizing die available. This sounds a bit on the large side to me. My bore does seem to measure a true .375/.376. I did make up a few rounds with @ BHN of 12-15 using Trailboss powder (lower pressure), both with and without powder coat. My test firings show no signs of over pressure. I want to move up to H4198 for closer to full power.

Am I on the right track with this? Anyone have any ideas, thoughts or comments on anything .375 and casting? Any input will be appreciated as there really is almost NO information out there about this.
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Old June 13, 2018, 05:44 PM   #2
Dufus
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First, if your barrel has a groove diameter of 0.375", you want a sizer die of 0.376 to 0.377".

Midway has a 0.377" sizer die.

https://www.midwayusa.com/product/12...e-377-diameter

Next, you need to use some caution in substituting 38-55 brass for the 375 brass. The 38-55 brass is longer than the 375.

Starline makes the brass, but they are out of stock for now.

I use the Starline 2.125" brass in my 38-55. If you get some of that, it really might cause a problem or two in your 375 Win.

You can use the 38-55 brass safely if you trim it to 375 Win specs.

I use IMR 4198, RE 7, and black powder in mine. RE 7 gives the highest velocity, but I keep my velocities as close to 1500 fps as I can.

The 375 Win is capable of 2000 fps with a 225 gr cast bullet.

If you need gas checks, Sage's Outdoors makes both crimp on and plain base gas checks at very reasonable prices.

https://www.sagesoutdoors.com/375-38...or-gas-checks/

https://www.sagesoutdoors.com/375-38...um-gas-checks/
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Old June 14, 2018, 10:38 AM   #3
T. O'Heir
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"...stupid prices to ship one or two boxes..." Shipping fees are set by the carrier, not the seller/manufacturer. Plus ammo gets Hazmat fees added.
"...pretty much an obsolete caliber..." Yep. Limited Production by Winchester according to Midway.
These guys make it from .30-30 brass. Isn't stupid expensive either.
https://www.eabco.net/375-Winchester...0_p_13543.html
There's some on Gunbroker too. https://www.gunbroker.com/item/774625134
"...are perfectly able to be shot in the Marlin .375..." Absolutely not. The .38-55 is a longer case.
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Old June 17, 2018, 10:11 AM   #4
zeke
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https://www.grafs.com/retail/catalog...ategoryId/930?
Bullets, Sierra made another run

https://www.starlinebrass.com/order-.../all-cases.cfm

You may b e able to trim a 38-55 case down, or reform a 30-30 case for lighter loads. Please note 30-30 brass does not have the thickness Win 375 does. Have never used the Starline brass.
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