I'm a recently retired Army officer & lifetime avid plinker/shooter/hunter who started transitioning from semi-auto military-style rifles to CAS guns about 10 years ago. Honestly, I'd paid zero attention to H&R/NEF until I spotted a .38-55 Target Model in a friend's gun shop about a year ago. Haven't shot CAS since retiring in '05--too busy with other priorities--but the gun & caliber appealed to me so I bought it! Didn't get around to shooting it until this summer. . .
The rifle was very erratic with Winchester factory JSP (.375)--about 1/3 to 1/2 keyholed. The first three Buffalo Bore .377 JSPs keyholed, so I stopped shooting this powerful premium round. Black Hills Cowboy (.377, plain lead) shoot fine, so I breathed a sigh of relief that I'd found a solution short of reaming, rebarreling, etc. (After the Buffalo Bore experience, I'd sent the gun back to the factory in case it was defective, but they fired a good three-round group with some unidentified ammo and returned it, along with an offer to replace the barrel with one of my choice if this December's run of Winchester factory ammo didn't resolve my problem. Maybe a Winchester change in specs is imminent???) Ten-X "Game Loads" (.379 cast with gas check) also shoot great, and their ballistics and bullet construction are obviously meant for hunting rather than CAS purposes.
My bottom line: I'm really glad so much great info was on GBO, which helped me conclude that time-consuming repairs or modifications weren't the only answer! (Reaming the chamber, etc.) Apparently, the cast bullets achieve obturation in my barrel (nominally .379, although I haven't slugged it), whereas the JSPs can't. The Ten-X Game Load ammo is certainly adequate for the whitetails I hope to encounter this season, and since there are no elk in my part of Louisiana :-) I don't really need the pure power of the Buffalo Bore ammo if I do my part with shot placement. I can cloverleaf the Ten-X at 25 yards, and am comfortable with making a 180 yard shot under good conditions. With Williams receiver sight and the trajectory of the round--plus my 49-year-old eyes--I think that's my max. . .and it's perfectly OK with me.
I'll reload with .377 and .380 cast bullets this winter, and see how they do.
Let me add that part of the reason I bought a H&R/NEF was a sentimental attachment to the first .410 I used to carry, my grandfather's H&R that my father inherited in the 1960s. Interestingly, it was marked ".44 caliber." Anyway, inspired by the entire single-shot idea, I bought my 11-year-old daughter a Versa-Pak this past spring, and she learned to shoot the .22 & .410 very well! That led to a .223 Superlight Youth with Red Dot scope for deer up close (no recoil!). . .and I even wound up getting her a Topper Jr. Classic 20 gauge for the weekend "youth-only 20 gauge" weekend right before blackpowder season opened. She'd progressed enough in her shooting that she was willing and able to shoot a slug & she was on-target at close range, if somewhat awed by the experience! So far, the deer are sticking to night navigation, but maybe that will change with the upcoming rut & we'll get some shots. Even when we're inside doing other things, we can keep a great selection of ordnance near our various doorways, ready to step out on the back porch if opportunity arises!
Regardless, I wouldn't trade the fun we've had shooting her new guns for anything. I also know she can keep them for everything from pests, to deer, to home defense in the future, and feel comfortable that she doesn't have to re-learn actions and safety procedures with a bunch of complex repeaters. She probably won't ever become a true aficionado who enjoys guns for their own sake like I do, but she'll be equipped for the basics & have some good memories to boot. I certainly will. I'm very glad that H&R/NEF fill the niche they do--I own & have owned some fairly expensive guns over the years, but could not have bought my daughter three different guns to fill different needs in a single year if I were plunking down $300-500 a copy!