[Rupert]

Originally Posted by Varyon

For import, proper reflex sights, as well as scopes, are likely (while locally-produced firearms aren't going to be as accurate as modern weapons, they'll still likely be accurate enough to get use out of some zoom). Hunters may get good use out of night sights/scopes. Targeting lasers strike me as unlikely - they're more useful when you don't have time to properly aim, but with muzzleloaders you pretty much always want to aim (as you are unlikely to get a second shot), and giving your target an increased chance to avoid the shot is a bad idea. If there are any issues getting reflex sights past space customs, however, targeting lasers could be a good alternative (although they'll be separated into a laser pointer and some device to connect it to the weapon).

Reflex sights will need to be imported, as they require a compact and robust source of high intensity light (such as a LED) and a compact power source (such as a modern battery), and probably won't be in much demand when maximum hit chances matter more than being roughly on-target very fast.

Telescopic sights will be in demand, but are outside local production abilities - people have been making the things since the late 19th century, but they weren't particularly good even in WWII, and that was about the earliest they were really worth using.

Outside of sights, rifle slings are likely (you want all the bonuses you can get when you've only got one shot), but can probably be produced locally.

Slings have been around for a very long time. Modern slings, designed for shooting more than carrying and so on are useful today mainly because the rifles are smaller and lighter, and because long route marches aren't common. If most of your time with your rifle is going to be spent marching or walking from point A to point B, and not in a tactical environment, you want a sling that's good for carrying the rifle on your shoulder, more than one that's perfect for bracing.

Suppressors, compensators, and flash hiders are unlikely to be available for the weapons, although a decent gunsmith might be able to get those designed for similar calibers to work for local weapons. Muzzle weights, despite being TL7 in Tactical Shooting, should probably be producible locally (one of those "high TL concepts that would be doable at low TL's").

Any of these could be made locally. However, the compensator isn't really needed, and the flash-hider irrelevant if black powder is in use (all that smoke can't be hidden, and there's not that much flash). A suppressor might be useful, though all that smoke makes hiding the fact a gun was fired hard, so most likely it's not.

It's in High Tech as the Accessory Rail, page 161. It's noted as TL7, but I suspect it would be doable at TL5 or so; if your firearms are standardized enough that identical models can use each other's bullets (as opposed to the user needing to cast his own bullets), I suspect you have the sort of precision needed to be able to make rails. Whether there's a real market for it may be a different question (those shooters who import fancy accessories may be well-served enough by just having their local gunsmith install the accessories).

Unless you intended to change the accessory load-out of your weapon a fair bit, a rail or rails is unnecessary and just added weight. As old-style rifles were pretty heavy anyway, I can't see this being popular, except perhaps with the fashion-sensitive if it gets promoted as the 'latest and greatest' from off-world.