question on .38-55 bullets

[coltnavy36]

Does anyone know.
All I have seen written on the .38-55 say's that it is for .379 bullets etc. or close to it.
Now, I see on the Midway website that most all of the jacketed bullets are .375, or .377.
What should one expect, as far as modern barrels for the .38-55?
I do not have one on hand in order to measure land and groove.
But as some are offered in .375, is it safe to say, it will shoot the same diam. as the .375H@H?
Seems the cast versions are .379, but jacketed are less.
Are the .375's going to mate up with the barrels grooves?
Thank's.
I'm new to the .38-55, so maybe someone can help here.
---coltnavy36---

[John Traveler1]

coltnavy36,

I too have been puzzled by the plethora of bullet diameters for the .38-55.

Here's the situation as I understand it:

Remember that both .38-55 and .375 Winchester are short-to-medium range (250 yds max) hunting cartridges.  Acceptable accuracy will be around 3-4 minutes of angle.

Loading manuals state that the old .38-55 cartridge used a nominal groove diameter of 0.377" to 0.382" and cast lead bullets are sized to whatever the groove diameter is, or up to 0.001" over.  Original lead bullet factory ammunition was undersized but used hollow-based bullets to give good accuracy in all bores.  Factory jacketed ammo used 0.377"-0.379" bullets as a compromise to give acceptable accuracy in both tight and loose bores, but is not known for fine accuracy.  Competition target shooters use handcast bullets and custom loads to get fine accuracy in this caliber.

A reason for the introduction of the .375 Winchester in 1978 was to improve the performance of the old .38-55 by boosting SAAMI chamber pressures and standardize barrel groove and jacketed bullet diameters at 0.375".  Modern .38-55 barrels follow this convention by beight "tight" compared to older barrels.  I've slugged several old Marlins and a couple modern Rugers and Winchesters and found this to be true.

Thus, the jacketed bullets currently available can be used in both .375 Winchester and still give acceptable performance in .38-55 rifles.

And yes, the lighter (200-270 grain) .375" H&H bullets can be used in the .38-55, but the long nose profile bullets have to be deeply seated to feed in lever action guns.

The slightly larger bullet diameters seem to have no unpleasant pressure effects in .375 W and modern .38-55, probably because these are medium caliber/moderate pressure cartridges with long throats that tolerate a bit higher chamber pressure.

HTH
John

[coltnavy36]

Thank's soooooo much!
This helps me more than you know, with knowing what I have to look forward to.