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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 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.


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.



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.


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.


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.

Good shooting and God bless.


As an aside, because I love the utility of the 38-55 when loaded to full power, I’ll include the following; I own one of each of the Winchester 38-55 commemorative rifles…..Winchester made three different commemoratives. (Chief Crazy Horse, Legendary Frontiersmen and the Oliver Winchester) These are very functional and highly accurate rifles. I did not care about their collectability, so I installed aperture sights and sling swivel studs and have used them quite a bit. With proper loads, these collectable rifles will shoot 1 MOA @ 100 yards, which is super impressive for lever action 1894 design rifles. If you run across any of these commemorative Winchesters, do not dismiss them as useless collectables. They are pretty prevalent on the open market, because folks do not know just how useable a rifle they are. Part of the great utility of the 38-55 is that with our full power loads, they are capable of taking any North American game including grizzly or large AK Yukon bull moose, but they generate only about 50% of the felt recoil (this is a guess based on how the recoil feels to me) of our full power 45-70 loads……just sayin.

Friends and Customers, 08-18-20


All shooters are being inconvenienced with what is happening to our society and the rush it is causing on ammo supplies. We have LOTS of ammo in stock and are making more at a huge volume on a daily basis. If our web site allows you to order any item, that means it is in stock—WE DO NOT TAKE ORDERS FOR ITEMS WE DO NOT HAVE! So, please do not email and ask if items are in stock. If they aren’t, the shopping cart will not take your order.

We have hundreds of customers to get orders to on a daily basis. In order for us to accomplish this for our customers, we ask the following.

  1. Be sure of what you are ordering. You are going to get what you ordered.

  2. Do not contact us and ask to change an order you’ve already placed. When we manually change orders it requires a lot of time that we do not have during this rush and it keeps us from serving all of our customers. If you’d like to change an order, we can no longer do that till things slow down, so simply place another order for more product, but PLEASE, NO MORE CHANGES after the fact!

  3. We NEVER have and never will take ammo exchanges or returns and then turn around and re-sale that ammo to unsuspecting customers as factory new ammo—this is not safe nor is it fair to customers who are buying what they think is new and safe ammo. No ammo is tamper proof! So please stop asking to exchange or get a refund for ammo you ordered, but have changed your mind about.

  4. Please do not contact us and ask for tracking numbers or “when will my ammo ship”? Our system automatically emails out tracking numbers on the orders we ship each day, however, because these emails are coming from a corporation shopping cart, many of these emails may go to your spam folder……..please look there. If it is not in your spam folder, that means we have not yet shipped. At current order rates, we are shipping within 5-7 business days of the time an internet order is placed. Please sit tight. Your ammo will arrive at the same time if you track it or not and will certainly arrive later if we are swamped answering questions instead of getting orders shipped. When 30-50 people per day send emails asking for tracking information and we have to pull that information up, then type it out and email it, it takes a huge portion of our work day that we should be using to ship those orders to customers in need. Please leave us alone so we can serve all of you. (ship to you) It’s a bit selfish, during times of shortages, when so many folks need to protect their families, to slow us down because you ordered carelessly or want to change your order. Right now, we expect you to do your part to help us all get the ammo we need in our troubled country.

These measures are hopefully temporary and will not be needed for long as we enjoy the interaction with our customers, so please, for the time being, be mindful of all those others who are also trying to get ammo during what I think is a societal meltdown/emergency. Hopefully, we can serve you all. We want you and your families to be armed and safe and we wish you the best during these trying times. My biggest concern is that things will worsen yet more, for a while. Until things straighten out in our government and society, we will have to streamline our customer service in order to serve all customers. Thank you for your understanding.

Good shooting and God bless,

Tim Sundles

I Understand