375 Winchester load help, please

My project involves a Winchester 94 Big Bore in 375 Winchester caliber. Original 375 Winchester brass (for length and neck thickness) has become hard to find and too expensive to buy when found. I have a supply of Starline 38-55 brass (2.080") and Lyman molds 375248 (255 gr. plain base) and 375296 (265 gr, GC). The rifle readily feeds up and chambers both of these boolits in 38-55 brass. What I am looking for is recommendations on powder selection and charge weights that may exceed the traditional 38-55 load levels in the published manuals, due primarily to the strength of the 94BB. My alloy supply includes pure lead, COWW and linotype, plus tin salvaged from solder. Powder coating may be an option as well. My goal is to create accurate hunting ammo. Thanks for you input.

375 Winchester brass is available from time to time, I hope you'll be able to find some. My 375 hunting load of Rx7 under a 375449 GC clone is max and I wouldn't recommend it in 38-55 brass without further research on your part. I've seen heated debates about the relative strength of 38-55 and 375 brass but I don't know. On paper the cases appear very similar. Traditional 38-55 loads are certainly accurate and adequate for most hunting. At the very least I'd trim the cases to the proper length. I can't use 38-55 brass in my 375 loads because I own rifles chambered for 38-55 as well as 375 and can't risk mixing them up. My KISS approach mandates proper headstamps in almost every case to help keep me out of trouble. I know folks do it but I'd spend the money on factory rounds to get cases if you can't find proper brass. Both cartridges are easy on brass so a few will last a long time.

Ken Waters Pet Loads article on the 375 Winchester had some pretty good loads and he liked IMR 3031 and RX7. Without looking it up I think 35 grains of 3031 was about his max and I used this as a basis for trying 33 gr in 38-55 and reformed 30-30 brass as a load for long range Cowboy Action shooting. It was very accurate in my Browning Single Shot with a 375449 and gas check and I used it out to 500 yards. Should be a great hunting load as well. 28 gr of RX7 with the same bullet did well also, but the 3031 load was more accurate.
McLintock

You might contact Starline and ask them about the differences in .375 Winchester brass and their .38-55 brass?

I was fortunate in that Midway was closing out .375 Winchester brass at the time I had JES rebore my Marlin 336W to .375 Win. I was able to purchase a full case of the .375 brass for a good price.

Hope this helps.

Fred

I have written (e-mail) to Starline several times about whether they will ever offer 375 Winchester brass. Never got a reply. All of the data sources who speak about the comparisons claim 38-55 brass is .007" thick at the neck/mouth, and 375 Winchester goes .010" thick. Apparently it is that extra .003" wall thickness that allows the shorter cases to run at higher pressures. Oh, well.....

How much of the Starline brass do you have?

Why worry about 375 brass use 38-55. See what Buffalo Bore Ammo has to say about their use of 38-55 brass. Using Our 38-55 Ammo in 375 Winchester Chambered Rifles
Using Our 38-55 Ammo in 375 Winchester Chambered Rifles

Our 38-55 ammo is designed to work in all 38-55 chambered firearms made with modern metallurgy for smokeless powder. It operates at 38,000 CUP—the 30-30 Winchester operates at an average max. pressure of 38,500 CUP. For those who are not aware, the 30-30 case is simply a necked down 38-55 casing.

OUR 38-55 AMMO WORKS IN ALL WINCHESTER 375 RIFLES

Our 38-55 ammo is also designed to work in ALL 375 Winchester chambered rifles. ALL means ALL. Winchester, Savage, and Marlin all chambered rifles in 375 Winchester. All 375 Winchester rifles utilize chambers long enough to accept the 2.085 inch 38-55 brass, even though 375 Winchester brass is only 2.020 inches long. By using the longer 38-55 brass, we accomplish two things:

1. We get the bullet closer to the rifling’s and this creates a generally more accurate load.

2. The longer 38-55 brass, with thinner case walls than 375 Winchester brass, gives much more case capacity and this allows chamber pressures to drop immensely. i.e. our 38-55 loads give the same performance (a 250gr. bullet @ 2000 fps) as the original 375 Winchester loading, but at only 38,000 CUP instead of the industry max. pressure of 52,000 CUP that the original 375 Winchester was rated at.

TIME-TESTED & WELL-PROVEN

The concept of using 38-55 brass to produce ammo for the 375 Winchester may be new to you, but it is not to us, so please simply read carefully and believe me. We’ve sold hundreds of thousands of rounds of this ammo and about half of it has been shot in 375 Winchester rifles. A couple years before I started making 38-55 ammo as Buffalo Bore Ammunition Company, I was shooting Marlin, Savage and Winchester 375 Winchester chambered rifles and was using good old every-day 38-55 brass in all of them. To be fair and give credit where it is due, it was both Brian Pearce and Mic McPherson that pointed out I could use common, readily available and affordable 38-55 brass to make full power 375 Winchester loads.

I’ve been doing it for almost 20 years now and have not over-looked anything. If I sound jaded on this subject, it is because I am. Trying to convince folks of anything new, can be a futile attempt, so I am publishing this short text on our site and those who choose to believe me are invited to and we would love to sell you our excellent 38-55 ammo for use in your 375 Winchester or your 38-55. You will love how it performs and you’ll be glad you found a source of high quality high performance ammo for your 375 Winchester. As a customer, we owe you this type of high quality ammo and this type of time conserving straight talk. In our 17 years of doing business as Buffalo Bore Ammunition, many thousands of 375 Winchester chambered rifles have gobbled this ammo up and I’ve not had even one complaint, which I cannot say for all of our ammo.

BARREL BORE

.375 BORE RIFLES

We use a bullet that is sized .377 inch. I am aware that 375 Winchester chambered rifles utilize a .375 inch bore. When fired, the .377 inch bullet will slug/size right down to .375 without raising pressures (we’ve tested the heck out of this) this is in part due to the construction of the bullet, but also due to our powder choice.

.381 BORE RIFLES

We are also aware that many old 38-55 rifles utilize a bore diameter of up to .381 inch, but most are between .377 and .380 inch. At 38,000 cup, there is enough pressure generated by this cartridge to cause that .377 diameter bullet to hit the rifling lands and slug up to the bore diameter (all the way up to .381 inch) and give wonderful accuracy.

HARD CAST SOMEDAY? - MAYBE

We’ve considered making hard cast loads for 38-55 also, (I personally shoot hard cast 270gr. bullets in all of my several 38-55 rifles) but they are too hard to slug up when fired, so the user would have to know his bore diameter and because of this and the numerous questions it would generate, I am still holding off on making any hard cast loads. Further, when firing hard cast loads, they are also too hard to size down to a smaller bore diameter without raising pressures and the thought of a customer trying to shoot a .380 inch hard bullet down the .375 inch bore of a 375 Winchester, has me a bit nervous. So to date, hard cast loads for the 38-55 are not in production and may never be.

If you email me and ask if what I wrote here is true, I will simply refer you back to everything I wrote here…..I will not tell you something more or different than what I have put in writing here on the site. What is written here is based on decades of my experience with my own rifles and with selling hundreds of thousands of rounds of this ammo to the shooting public…… Thank you for carefully reading this information.

A friend and I worked with his 375 big bore quite a bit last year. The FIRST thing we did was a throat cast. 375 Winchester brass is too short for his chamber for best results and we used the long Starline 38-55 brass and trimmed to fit his chamber. The throat of his chamber measures .3795" and the bore is .377". Yours may be different. The freebore of his rifle is quite long also. The thinner 38-55 brass allowed us to use a bullet fat enough to fill the throat where the 375 Winchester brass will not. Tom at Accurate molds owns a 375 Big Bore and has catalogued a mold which fits his rifle. My friends rifles' throat matches the one Tom has pretty closely. We haven't pushed the loads to the point that overpressure might be a concern and don't feel the need to.
Good Luck with yours,
Rick

A few years ago, I worked with a Marlin 375 and found that the chamber would accept 2.080 cases with a touch of room to spare, and the following load was fired in 2.080" .38-55 cases without problems. A Lyman 375248 cast of air-cooled WW, paper patched with drafting vellum and sized .378 over 28gr of AA 1680 was 100% load density AND A MAX LOAD in that Marlin. The usual warnings about start low and work up apply. Groups were 1.5-2" at 100 yards. Plenty of muzzle-thump for anything in the mid-western states, generally.

I have used Starline 38-55 brass in my #3 Ruger for several years, .375 Winchester data, 200 grain Sierra, max load of Rx7. After many reloads, I have not lost a single case. Zero pressure signs. I made an inquiry several years ago and their ballistician, Hunter Pliant stated that though they were aware of people using their 38-55 brass in 375 Winchester, they have not tested their brass to .375 pressures. Worse comes to worse, use the available 38-55 date, it will anchor about everything in the lower 48 with little fuss.

It's not just the brass thickness at the neck that is different. 375 brass is thicker in web and sidewalls, which makes it preferable for high pressure loads. If you do a google search there is a comparison of 375, 38/55 and 30/30 brass - all sectioned to show the web and sidewall differences. Long story short, 375 is heavier followed by 30/30 then 38/55.

I've only used Winchester 38/55 brass and to me the thinner sidewalls were quite apparent at elevated pressures, so much so that I relegated 38/55 brass to low power loadings. I do use a lot of reformed 30/30 brass and apart from being a little short, seem to work well at high pressure. The other point is that not all 30/30 brass is created equal. I've examined quite a few brands and of the examples I've checked the best was PMC (no longer available) followed by Winchester. I have never sectioned Starline 38/55 brass, so it may be better constructed than Winchester 38/55 brass.

I pretty much only use Reloader 7 for all my high pressure loads. For me it produces the highest velocities of the powders available to us and provides good accuracy. For low power loads I really like 6.5gr of Red Dot behind Lyman 375248. It's barely sub sonic and very accurate. It's a nice plinking/small game load.

The other point with this chambering is that it has a really long throat, which is enormous compared to other levergun rifle chamberings (excluding pistol cals). I find the largest diameter than fits the chamber and still cycles really helps align the bullet to the bore and provides the best accuracy.

cabezaverde- I checked the shack and found I misquoted my brass supply. Mine is W-W Super brass, have 100 rounds. Still yet I question whether this or the Starline is the thicker, tougher, stronger brass. Regardless of which fits this definition, I will start lower and work up gradually, hoping for group size first and speed second.

LimpingJ - I was aware of this article and could only, as Jimmy Carter once said, "lust in my heart" for their load data. Seems that I recall they are rather jealous of their data which also translates into "why give away the reason people buy our product?" I have to respect their load development and will settle to work on mine. After all, who wants to go through all the labor of loading - firing - repeat a gaggle of combinations in search of that one special combination that gives you what you are hoping to find. I don't know whose brass Buffalo Bore is using, or really if either one brand is better than the other for this application. While my molds are in the 255 and 265 weight range, I have seen that Accurate offers lighter weight patterns and am starting to explore that possibility.

Jeff - I appreciate your note about the durability of the Starline brass. At this time I suspect my 38-55 brass will be dedicated toward working up boolit loads. In the event I gather any more 375 Winchester rollmarked brass I will test these also with heavy loads under boolits that go beyond the posted limits for 38-55 brass.

Again - my thanks to all for their input on my request for input. MUCH appreciated.

If anyone finds themselves with an oversupply of the Starline 38-55 I could trade some unfired 375 Winchester for it.