I’ve hand loaded .375 Win for a couple decades, and started loading .38-55 about a decade ago.
Let’s split the discussion into factory ammo and then hand loading for the .38-55.
Factory ammo is not common and is generally expansive when you find it. I found this box in a gun shop in Mitchell SD last week. It wasn’t on the shelves out front, it was in back where they keep ammo specifically to be sold with guns they sell in the same caliber. It’s harder to sell a gun when they can’t also sell ammo with it. In this case I bought a Winchester 20” take down rifle in .38-55 and they offered me the box of ammo. It was expensive in terms of costing $3.50 per round, but technically a deal because it lists for $89 on the Buffalo Bore website - $4.45 per round.
That makes the .38-55 a handloader‘s proposition.
I bought it mostly because I’ve heard a lot about it and because with a 250 gr bullet at an advertised 1950 fps (albeit in a 26” barrel) it’s only a couple hundred fps behind the .375 Win in Winchester’s 200 gr loading (and they only make a small run of it every 7-10 years) and is about equal to the discontinued Winchester 250 gr load.
In terms of factory ammo, the traditional loads have used a 255 gr bullet. Originally the black powder era .8-55 launched that 255 gr bullet at 1320 fps. A smokeless powder “High Velocity “ load superseded it with the same bullet and a velocity of about 1590 fps. Winchester discontinued .38-55 rifle and carbine production in 1940 and by the time I was a sprout interested in guns in the early- mid 1970s it was a dead caliber for all but the die hard fans and shooters.
But even then, you could still fire from a .30-30 case to usable .38-55 dimension, it was just a little short at about 2.020”, compared to the original 2 1/8” (2.125”) .38-55 case.
However, in 1979 Winchester made a trio of .38-55 rifle replicas and started selling .38-55 ammo for them in various matching commemorative boxes.
They also introduced the .375 Winchester which was based on the .38-55, but operated at higher pressure. Since the Model 94 could not accommodate a longer case, Winchester took a different approach to prevent problems when using factory
.375 Win in a .38-55, or when using factory
.38-55 in a .375 Win. (More on the factory
Winchester used a .375“ bore and bullet diameter in the .375 Win, and a shorter 2.020” case length. I suspect they used 2.020” because it probably let them make the case on the same machines using the same parent case stock as the .30-30. However, they also gave the .375 Win chamber a long and large diameter throat and a long tapered leade that allowed a .38-55 cartridge to chamber and still be able to release a larger diameter .379-.380” 38-55 bullet, and then allow it to size down to .375” without exceeding .375 Win pressure.
The new production .38-55 ammo also used a .3775” bullet to go with the smaller .3775” bores used in the new rifles, along with the “short“ 2.080” .38-55 case. Those new .38-55 dimensions made it possible to fire the new .38-55 ammo in the .375 Win with no I’ll effects. In fact Buffalo Bore’s “heavy” .38-55 ammo is advertised for use in the .375 Win. They use the short 2.080” case and a .3775” bullet and even their high pressure “Modern .38-55 only“ rifle loads are safe for regular use in the .375 Win.
Hand loading for the .38-55.
As noted above, prior to Winchester making .38-55 commemorative rifles and commemorative ammo for them, cases for the .38-55 had to be specially made or you had to fire form a stand in from .30-30 brass.
During the 2016 component shortage I did exactly that with a couple hundred new Winchester .30-30 cases. The method I used was 9 grains of Unique with cream of wheat filled on top of the powder to the bottom of the neck, held in place with a pea sized wad of toilet paper and then fired vertically so the brass flowed evenly.
I trimmed them all to 2.020” and then compared water volume with a sample of .375 Win cases and found that while the average volume of the .375 Win cases was slightly smaller (this thicker case walls) there was significant overlap (about 2/3rds of the cases) between the .375 Win cases and the .30-30 fire formed to .375 Win cases.
But Starline also started making .375 Win cases as well as both the long 2.125” and short .2.080” .38-55 cases and I bought 500 of the .375 Win and 2.080” .38-55 cases.
You also used to be a be able to find .375” round nose or flat nose jacketed bullets intended for the .375 Win from Barnes, Sierra and Hornady in 200, 220 and 250 gr weights.
Unfortunately for .375 Win shooters jacketed bullets started to become hard to find after the 2008 recession and election related ammo and component shortage and they are now still very scarce. Hornady hasn’t helped as they have moved the .375 Win into the ”obsolete” category and no longer make a bullet for it.
That makes cast bullets more or less the only game in town. That creates some issues for the .375 Win in terms of getting anywhere near full .375 Win performance with even a gas checked bullet. Winchester used a fast 1-12 twist (the same as the 30-30) for no apparent reason. Consequently you have a .375-376” cast bullet that must be cast fairly hard to both match the pressure of the load and more critically to not skid in the fast rifling rate after getting a pretty good run at it in the long chamber and throat. That bullet is also fired in a large diameter throat designed to accommodate a bullet up to 380”. That hard and .004-.005” undersized (relative to the throat) consequently won’t bump up to the throat diameter so it experiences significant gas cutting with resulting lead deposits in the bore.
You can get decent accuracy from it, but it takes a careful balance of alloy hardness, load pressure and bullet diameter to find a sweet spot that works, and it won’t usually happen at pressure levels that match .375 Win jacketed bullet performance.
That’s what led me to just start loading and shooting .38-55. Winchester and Ballard used 1-18” or 1-20” twist rates in their rifles and Winchester used a 1-15” twist rate in its .38-55 commemoratives and still uses that twist rate in its current production .38-55 rifles along with the .3775” bore diameter. That makes them better suited to jacketed bullet use, due to the slower twist rate and the ability to use a .379” cast bullet.
Uberti uses 1-18” twist and a .379” bore diameter in its Model 1894 .38-55 reproductions. It’s in my opinion and experience the ideal current production 38-55 rifle for use with cast bullet loads as you can use a .380” cast bullet as originally intended for the .38-55 cartridge and chamber.
But there’s no free lunch and some folks complain about poor accuracy with the Uberti rifles using .3775” jacketed bullets in the .379” bore. You need to use a modern load like the Buffalo Bore “Heavy“ to get a jacketed bullet to properly obturate in the larger bore. But it’s really intended to be used with traditional cast bullet loads and it does that exceptionally well.
Cast bullet wise the Lyman 250 gr 380681 mold works well for the .3775” bore rifles as does the Lee .379-250 mold.
The Lyman mold is no longer a true .380” mold despite the number and as with most molds the bullet diameter is based on an assumed use of Lyman No. 2 Alloy. Softer alloys shrink a little more so a 1-40 alloy that works well in the .38-55 will be a bit undersized in an Uberti or vintage Winchester, but normally bumps up with no issues, particularly if you use a card wad or polyester wad under a plan base lead bullet.
There is also a wide range of commercial cast bullets for the .38-55 in diameters from about .376 to about .381” in both plain base and gas check designs, and in weights from 240 grains to around 330 grains. Just be careful in your alloy selection to match the alloy to the load pressure, and don’t make the mistake of thinking “harder is better”.
Powder wise I get great results with Reloader 7. I also like using Unique for black powder performance loads, without the black powder mess. I use a 3/4” x 3/4” square of 1/4” polyester quilt batting stuffed in the case between the powder and bullet to both take up the extra space in the case and also provide some protection for the bullet.
All things considered the .38-55 is one of my favorite cartridges as it allows you to load up mild recoiling 245-250 gr black powder velocity loads for casual shooting or use a 260-275 gr gas checked bullet at high velocities for superb performance on deer and black bear sized game, or when you can find them, jacketed bullets at “heavy” velocities that will take anything on the continent at reasonable lever gun distances.