Buffalo Bore offers a 255 grain jacketed flat nose 38-55 @ 1,950 fps and a 270-grain lead flat nose @ 1,900 fps. Based on their literature, both loads deliver 2,044 foot-lbs. of energy. Although I don't hunt (I'm not against hunting, it just never interested me like fishing and other pursuits), I do enjoy target shooting immensely. Having said that, I will relay some information regarding the 38-55 which will hopefully prove useful and not too boring. Some of the 38-55 loads I have chronographed are presented later in this post. If I were a hunter, I don't think I'd hesitate to use the 38-55 for deer, just based on the penetration I have observed from hard lead bullets through 6X6 and 8X8 blocks of dense treated wood, even at very modest velocities. A 38-55 can be loaded to .44 Magnum power levels and beyond, and the sectional density of a 245- to 265-grain 38-55 bullet is higher than the 240-grain factory load in .44 Magnum (which is a great brush cartridge for whitetail). The 38-55 has most definitely been used to take black bear and elk in its long history, but if I were after something that dangerous or that big, I don't know if I would opt for a 38-55. The choice on that is up to the individual hunter, I guess.
I shoot a Wesson & Harrington single shot 38-55 and it has been a real experience trying to get decent accuracy with cast bullets. After a whole lot of experimentation, I have come to the conclusion that I may never get decent groups from plain base, soft lead bullets in this rifle. My best groups to date have been with hard cast, gas check Leadheads, Bonus, and Cast Performance bullets. (I guess I ought to learn to cast my own bullets, but that's one thing I haven't attempted yet). Based on my admittedly limited experience with the 38-55, it is a mystery to me how people get good groups with anything other than hard cast gas check bullets - how the Schuetzen guys and black powder shooters do it, I just don't know. Apparently, I still have a lot to learn about the 38-55.
Recently, I have been consistently shooting 0.75-inch to 1-inch groups at 100 yards with 265-grain Leadheads gas checks (which have a hardness of 20-22 BHN) driven by 27.0, 28.0, and 29.0 grains of Reloader 7. These are 5 shot groups, measured center-to-center. I also shot a 3.6-inch group at 300 yards (4 of the 5 shots went 2.8 inches, center-to-center) in September with the 28.0 grain RX7 load. That was the first and only time I have tried the 38-55 at that range. It took every click of elevation in the scope to get the bullets on target at that range, but one shot was precisely in the center of the target (needless to say, I was elated). I would like to believe that the single "flier" in the group was the result of wind drift in the long flight downrange, but there was actually very little wind that day.
The strange thing about the Leadheads bullets is that they are .377" in diameter, and the rule of thumb for lead bullets is that they should have a diameter .001" to .002" greater than groove diameter. However, the groove diameter of my Wesson and Harrington is over 2 thousandths greater than bullet diameter (groove diameter is .3795" and bore diameter is .375"). Go figure! I have tried lead bullet diameters from .376 to .381 inches. The .376's tumbled and .377 plain base bullets exhibited tipping at 100 yards, but obviously the .377 gas checks from Leadheads are very stable and accurate. Any bullet - with the exception of a very heavy, long bullet at low velocity - measuring .378 to .381 is generally stable (but not necessarily accurate) out of my 18-twist barrel. The only problem is that I have to neck turn Winchester brass in order to chamber a round loaded with anything larger than a .379" diameter bullet due to the very tight chamber in my rifle. Therefore, I tend to hand load only .377 to .379 caliber lead bullets, because it's a lot of trouble to reduce the case neck thickness by outside neck turning.
With regard to accuracy, when I sent my rifle back to Harrington & Richardson for a trigger job, the factory shot two 3-shot groups at 100 yards using factory-loaded Winchester 255-grain soft point ammo. The two groups measured 0.4" and 0.6", center-to-center. Those jacketed factory loads are very mild at 1,320 fps (a typical black powder velocity), but obviously very accurate and adequate for deer. I believe I am correct in stating that .377 and .378 Barnes and Boer jacketed bullets are available for reloading in the 38-55 (you might want to do a search on the Marlin Talk forum for additional information), but I have not tried either in my rifle. I want to see what kind of accuracy I can wring out of cast lead bullets first.
I haven't chronied the Leadheads 265-gr. gas check bullets that gave 0.75- to 1.0-in. groups with Reloader 7, but here are group sizes, velocities, and foot pounds of energy for some of the loads I have tried over the past year:
I got 1.0 inch center-to-center at 100 yards with 28.0 grains of Reloader 7 pushing a 260-grain Bonus gas check bullet and 1.1 inches (c-to-c at 100 yards) with the same bullet driven by 28.0 grains of H322. These were 5-shot groups. The velocity (measured at 10 feet from the muzzle) of the RX7 load was 1,843 fps and that of the H322 load was 1,702 fps, which equates to 1,959 and 1,671 foot pounds of energy, respectively. Velocity and energy at the muzzle, of course, would be slightly higher.
The average velocity of 260-gr. Bonus and Cast Performance gas checks driven by 18.0 grains of 4198 was 1,351 fps. For some reason, I failed to measure the velocity of any heavier loads of 4198 in combination with gas checked bullets. However, the velocity of one load (which yielded a 5-shot group size of 1.3 inches at 100 yds.) would probably have been in the vicinity of 1,600 fps: this load consisted of a 255-gr. plain base lead bullet over 23.5 grains of 4198.
Cowboy loads consisting of a 245-gr. lead bullet over 7.0 to 8.5 grains of Red Dot gave velocities of 1,068 to 1,168 fps and groups ranging from 6.5 to 2.0 inches at 100 yards. At the time, I felt I could do much better by seating the bullet further out. I have since tried 10 grains of Red Dot with a 235-gr. plain base bullet, which resulted in a 5-shot group size of 1.6 inches at 100 yards. However, I'm still experimenting with seating depth and powder charge, and even thinking about using a filler or a wad to see if that will improve accuracy. The Red Dot is extremely clean burning, incidentally.
15.0 grains and 17.0 grains of 4759 with a 265-gr. bullet gave 1,363 and 1,466 fps, resectively (@ 10 feet).
18.5 grains of 4227 gave 1,327 fps with a 250-gr. bullet @ 10 feet.
22.5 grains of 5744 gave 1,569 fps with a 260-gr. bullet @ 10 feet.
29.5 grains of 3031 gave 1,617 fps with a 250-gr. bullet @ 10 feet.
Incidentally, the barrel on a 38-55 Wesson and Harrington is 28 inches, which of course means that velocities will be higher than the same load in a shorter-barreled lever action.