Standard 38-55 factory loads are usually loaded with a .377 bullet. I am not sure what you want for components, but there has been some discussion on the brass length and the SAAMI is 2.085. That is the less expensive brass that Starline sells and is quite adequate. Lots has been written about the differences using the "shorter" brass. Those that buy the longer brass often end up trimming it back a bit. Personally I feel its a big ado about nothing. The long brass has been called single shot brass by some.

I have a Marlin Cowboy, which was modern made. Been some discussion about its bore but I get by fine just shooting the Barnes .377 Jacketed and my cast sized to .379. Someone said once that the factory standard was .378 for the Marlin barrels. I slugged it and got something very close to that. More importantly, those bullets are what works for me. Early Winchesters could be all over the place for bore diameter but the Miroku is probably made to the specs they quoted at .376-.378. I also use the 2.085 SAAMI case length. That would be a good starting point for your rifle. The rule of thumb for cast is to use .001 over bore diameter. Even for cast bullets I buy I treat them with Lee's Liquid Alox so that would not be a bad thing to buy. Its very simple to apply as you put the bullets in some sort of tray and add a couple of drops of LLA and roll them around until they are coated. Some like to use larger diameter cast bullets that are often .002 or so over bore diameter.

Most recommend RCBS cowboy dies for reloading the 38-55. Some use the Lyman M-die. In all likely hood the rifle is built to SAAMI specs. The Barnes J bullets will slug to the barrel with heavier loads. Cast bullets may require a bit of experimentation for individual rifles. f

DEP

 

They both may be correct. I am not saying they are but could be. Bore MIGHT be .367 with groove diameters.376 or .377. The number you are concerned with is the groove diameter. It is a starting point with cast. Some rifles like a diameter that is the same as the groove and a soft alloy to bump up. Some like a fat bullet that is slightly harder. For me the “fun” of cast is spending lots of time finding “that load” for these guns then put them in the safe and haul em out a couple times a year. By the time I have found the answer to what cast load a gun likes another one has come home and is next on the list. Do you know how to slug the bore?
Good luck.

 

I concur with Northmn!! I have found that factory reps, like the clerks at the big box sporting goods stores, are idiots!!

 

This is the latest I got from them:

Bore Diameter - 9.347mm = .368" +/- .02"

Groove Diameter - 9.55mm = .376" +/- .02"

Does this sound right?

Thank you.

 

I tried to get chamber dimensions, but no luck.

 

Plus or minus .02" is like a mile in gun tolerances. That span is thicker than the wire of a paperclip. I'm sure that they meant +/- .002". Even then +/- .002" is TWICE the tolerance set by SAAMI. I suspect you are dealing with someone who has no business speaking to that subject. ALL American gunmakers worth a hoot comply to SAAMI. European makers follow CIP. To do otherwise surely invites litigation should something go horribly wrong.

SAAMI allows access on line for the specs of chambers and cartridges.

https://saami.org/technical-information/cartridge-chamber-drawings/


AC

 

Thank you. The bore diameter they're giving me doesn't coincide with SAAMI. I'll be sure to mention it next time I communicate with them.

 

We are talking about a hunting rifle not a long range bench rest rifle. A 376 bore would permit use of Winchesters factory rounds. A -.002 would be a 374 barrel which would be very tight for a 377 bullet. The 376 bore is used by JES when he rebores rifles, but he does this to permit the 38-55 and 375 to be used interchangeably as I understand it. It would also permit the use of jacketed bullets designed for the caliber which were mostly 375. But as Gunscrewguy stated, modern rifles are to be built within SAAMI specs. If you are lucky you may get a Winchester 94 that will give decent 5 shot groups, but they were never made to be bench rest rifles. Often the best way to sight in a 94 is to fire one or two shots and let it cool down and fire a couple more. Those that get tight groups from either a Marlin or a 94 often have to do some accuracy work to relieve stresses.

To get the top accuracy you will have to experiment a bit. Start with SAAMI compliance. Which means cases of 2.085 length. Slug the barrel. My Marlin CB shot 375 Barnes jacketed bullets, but with hotter loads. It likes 379 cast. Larger diameter bullets would not chamber with Winchester cases. As I had more than a few Winchester cases I went with the 379. It is as accurate as I can shoot with receiver sights. I found loading procedure and alloys, and powder selection to be most important. You will have to slug the bore to put your mind at ease. The best a company rep can tell you is that it is built to certain tolerances. Above that you will have to find its sweet spots.

DEP

 

They’re saying bore diameter is .368”,

 

That may be true. However the "Groove Dia" will be more like .377 - .379

The 38 in 38-55 does mean .38 cal.

 

Bore is .368”, not .376”.

 

Caliber designations get pretty interesting. Rough rule of thumb is that grooves are .004" deep giving a .008 difference in some calibers. The very common 30 cal is designated as such because if yoy subtract the .008 from the .308 bullets they take you get 30 caliber. .368 with .004 groove depth is a .376 bore or would take a .376 bullet. As Winchester has manufactured 38-55 ammunition for years that uses a .377 jacketed bullet at BP velocities I would suspect they may be using something close to that bore. There is no .368 caliber made. The 9.3's take .366 bullets. A .368 bullet would rattle down the bore and would probably key hole.

I have no direct experience with the Miraku 38-55 but suspect it may be .377 bore to match the Winchester factory bullets. While SAAMI may have established a standard the bores of 38-55's have been known to vary. I saw a Uberti High Wall copy that had a .381 bore and would keyhole anything close to .377.

I looked up some archives on the Cast Boolits site and the Miraku's made to copy the 1885 single shot had .376 bores. One claimed a 3764 bore. One individual stated that anything with a .377 bullet shot. Sounds like the information you are getting is what they use. One said it had a .368/.376 bore (.368 land to land/.376 groove diameter) Using cast your 94 should be able to use anything in the .377-.378 range. Don't get too excited about case length. JBledsoe did a lot of accuracy work with the 38-55 and scoped his rifles and modified them a bit and could get 1" groups. He did not mess with the "long" cases. The 2.085 cases are cheaper anyway. Get the RCBS dies or another set with the Lyman M dies for case expansion.

Again you have a 94 Winchester. I have seen some threads where the individual is agonizing over 1.5 -2" groups at 100 yards. That is pretty good for a old lever action hunting rifle. The 38-55 out of a single shot is another matter and could likely do that at 200, but with very technical loading.

DEP

 

Don't forget the type of rifling. It's been a few years, but as I recall ...

Bore was the original hole diameter. A .45 cal barrel had a .45 hole and you cut grooves into it at the smiths preferred depth. .002 grooves would cause a .454 groove diameter. .30 cal bore with .004 grooves caused a .308, etc.

Button rifling came along and changed that. When you push a button through it presses in the grooves, but displaces metal for the lands and creates a tighter bore than the original drilling. Depending on the era of the rifle, it can create some strange dimensions.

I once had a Martini action with a custom barrel chambered in a .38 black powder cartridge that had. .385 groove diameter and .375 bore. As a young pup I couldn't figure out what it was. I had an old gun smith told me it was an early button barrel attempt and probably one of a kind. He recommended a soft lead grease patched bullet and a shortened .38-55 cartridge. It was all over my head at the time, so I traded it off. I wish I would have kept it. Who knows what it really was, but I expect it was European in origin.

 

Check out the Chamber Specification drawings on the SAAMI website.
Then read on the Starline brass website under Archived Articles about 38-55.

 

If you have not purchased cerrosafe, do. Remove all doubt and make a chamber / barrel cast. Midway has great instructions on how to use and they sell the stuff.

Bullets, cast or jacketed, between 220 and 260 grains are good choices. 5744 and 4198 are both outstanding powders for the cartridge for loads in the 1,350 to 1,550 fps range. Trail Boss and Unique are great for BP load duplication, less than 1,100 fps. Rel #7 if you want/need more heat.

I have a Miroku 1885 and the groove diameter is .377". My Marlin 336CB has a larger groove diameter, .379".

The older rifles had chamber length and groove diameters different than the modern rifles.

I would suggest the longer Starline brass. If needed, you can always trim a little off. I would propose you will not need to trim the 2.125" brass.

 

Ok...so the SAAMI Minimum Chamber Dimensions are as follows:

Bore .373 +.002; Groove .379 +.002; Length 2.2153 +.015.

Does this mean that my Winchester's bore is way undersized at .368"? Would it be safe to shoot the Barnes bullet, even at the lowest starting loads I can find?

 

That cerrosafe sounds like what I need to use to ease my mind. Shouldn't come to this with a modern, new production rifle.

Thank you.

 

Wonder what the new Henry 38-55 is bored. JES and winchester appeawr to have found a good comprimise that handles most factory stuff available. Barnes makes two OS bullets, the .375 for the 375 Winchester and the .377 for the 38-55. I have shot both in my Marlin Cowboy and they both worked. The .375 seemed to slug fit enough give adequate hunting groups. The tighter bores that seemed to be offered now work with about anything and take away some of issues with the caliber if one is using a new rifle. The old ones gave some fits and that Uberti was probably a copy of an original. I wonder what they would slug out now?

I read Starlines article about case length and came to the conclusion that it helps him sell brass. It might matter with an original target rifle or old lever, but I doubt if it means anything in a newer rifle. My Cowboy seems to shoot at the same point of impact using either Winchester or Starline brass. I can chamber a larger bullet with Starline but don't need to.

DEP

 

Does it make sense to think Starline's brass would provide less neck tension? Does it matter when you're crimping anyway? Would the difference in case capacity allow for different optimal powders, or is it insignificant?

 

When I started this thread, I had read enough about the .38-55 to be absolutely confused. I have read some more since then, which (together with this thread) has given me some clarity. Regarding the bore/chamber in my rifle, I'm going with the opinion that it can in no way be other than at SAAMI specs.

My conclusions:
Assuming modern rifles manufactured to SAAMI specs, unless one wanted to use their .38-55 rifle as a sniper rig, the short brass is fine. The 255 gr. Barnes .377" bullet should be safe at moderate velocities and provide sufficient accuracy for hunting at this cartridge's traditional distances. For playing around and going for better accuracy, trying different size lead bullets is necessary in addition to the standard powder and bullet weight variations. Distance to the lands, primer brand/type, etc., should be left to rifles other than my '94.

Thank you all for the help provided.

 

I tried the same load, powder and primers in Starline brass and found an insignificant difference over the chronograph if any and the same point of aim when compared to Winchester cases. Starline is about the only game in town if you want to order brass. Two things make the 38-55 confusing. One is the use of cast bullets which can make about any caliber confusing as you run into theories about how much over size to use and alloys. If you buy cast bullets, which is a good way to start out, then one can try a couple of different diameters. My guess is with what I have read and seen on the input of the Winchester one could try .377. Alloys are for those that cast their own like I do. The Barnes bullets make great hunting loads and expand well on deer. Vollmer makes 38-55 bullets and makes them at different weights also. Have to contact him on the Web, Vollmer-bullets, but he is currently on hold pending licenses for a new location. Midway USA is a source for cast bullets and others have their sources that are more direct.

A good load that many use for a nice shooting combination is a 250 grain cast and 9-10 grains of Unique. Other powders that are good is 4198, 3031 and Re7. 3031 is good for the more hefty loads. I am willing to bet that your rifle will handle either Barnes diameter as My Marlin Cowboy did, but I am sure that the heavier load slugged the .375 bullet, the .377 works just fine in my Marlin Cowboy which is a newer made rifle. It is an interesting cartridge and not really that difficult to load for and is one of the better cast bullet cartridges out there. It started life as the 35-50 Ballard and was a popular 200 yard target cartridge. While 200 yards might be a bit of a challenge hunting it is doable with a range finder or at known ranges. If you look at a ballistic table the heavier 38-55 bullets retain velocity very well. Enjoy the rifle and don't overthink things too much.

DEP

 

Vollmer...I'll make a note of that. I do have all those powders, so I'm all set in that respect.

Thank you.

 

I just noticed Henry is making a side loading .38-55 , .35 Rem and 30-30. Might have to hang one on the wall. 🙂

 

I have a new Miroku Winchester 1894 Sporter. I use the short Starline brass and size my bullets .379 with a NOE Sizer. I get excellent accuracy and velocity with 4 different cast bullets and Reloader 7 powder.

 

I have a new Miroku Winchester 1894 Sporter. I use the short Starline brass and size my bullets .379 with a NOE Sizer. I get excellent accuracy and velocity with 4 different cast bullets and Reloader 7 powder. View attachment 758507 View attachment 758509 View attachment 758511

If that works for you, it should work for me. Thank you.

 

Hello; I use a H and R single with 250 bullet sized .379 and Winchester short brass with blackhorn 209 powder. Shoot the same load from Winchester Mirou and get a louder bang more recoil and faster velocity. Bore is tighter with smaller chamber. The Marlin CB is big chamber and larger rifling needs fat bullet. A Pedersolie rolling block is just right with perfect bore and rifling and accuracy.
Kinda like the four little bears , pick the porridge that you like.

 

HI; Regarding brass length- H+R single had to use brass trimmed to 375 Winchester length as the 2.085 brass jammed into the rifling. Tried 375 Winchester brass but was too thick for the bullet diameter and would not chamber. As to accuracy, it was better with shorter brass.
Every 38-55 is a rule onto itself, chambers, rifling, loads, YA gotta love frustration and have time on your hands to play around to get em to work.