...With a 30-30 in an original 30-30 about all you have to worry about is bore condition and headspace... [will] warhorse withstand a barrage of modern ammo... steels weren't as strong as they are now. THIS is a GIVEN.
38-55 loaded to express type loadings are far superior to the 30-30 in terms of bullet weight, penetration, and cross section. However, bore diameters can be all over the place ...
Twas me, I'd leave that 36 alone....don't see many around these days.
The 38-55 is a great round but if you don't do your homework you'll find yourself embedded in a money pit of frustration...
Good post, a lot in it... I didn't know much about the 38-55 until I came to these forums (except that it begat the 30-30). This thread prompted me to read a little on this cartridge. The following is probably not news to most
Bore size of 38-55s vary from .375 to .38, with most around .375, .377 or .379. Thus each rifle is a bit unto itself, though I'm sure Marlin's current offerings are standardized. Once all that is worked out, it is very accurate, not unlike the 30-30.
Ammunition offered: For 38-55, it is a 255gr bullet, MV 1320fps, SD .259 and point-blank range of about 135yds, zeroed at about 115yds. Standard max handloads with the 255gr bullet yield MV around 1550fps, pbr - 150yds, z - 127yds.
Among 30-30 offerings, that is equivalent to the standard 170gr load in 30-30, SD .256, MV 2200fps, point blank range - 207yds, z - 177yds (approximate for both ammunition and recommend handloads). There are various pet handloads for both 38-55 and 30-30, hotter and milder. But apples to apples, this is how it stacks up.
Penetration and expansion: as we've seen the sectional densities are about the same. So we'd expect penetration to be about equal with similar type bullets. But taking into account velocity and expansion that may not be the case.
The 30-30 performs very very well, with remarkable consistency; perfect mushroom expansion with deep (usually complete) penetration. I would expect the 38-55 to have very little, if any, expansion beyond 50-60yds and penetration like there's no tomorrow.
All in all, maybe the 38-55 would best be compared to larger bore cartridges, as .308 is upper small bore and .375 is lower large bore.