It is best to use the proper twist barrel for conicals, not an in-between twist. If you are happy with substandard accuracy, and perhaps NO accuracy at long range, then stay with the in-between twist. The shallow, .004" deep rifling makes the 48" TC twist, an in-between twist. It isn't deep enough to properly hold patched RB like the original Hawken's did, yet is a bit too slow in rate, for proper stabilization of conical bullets. A faster twist will shoot them better. In .50, the twist should be at least or faster than 36" for bullets in the 450gr. range. I just feel there is a limit to the accuracy you can expect from the slow twist with slugs.
: You may achieve 3" to 4" at 100yds. but the real test is at 200yds. How well does it shoot at that range. I would be much surprised if the slugs weren't keyholing at that range. The 48" twist is barely enough to keep the slugs point-on at 100 - let alone any further out.
; My last .50 slug barrel had a 24" twist, made by Harry McGowen, of St. Anne Ill. It achieved 1 1/2" 5-shot groups at 100yds. and exactly the same group size, 1 1/2" at 200yds.- off the bags of course. This means it was shooting 1 1/2 MOA at 100, but only 3/4 MOA at 200yds. My sights were hooded aperature front sight with Tang aperature rear sight.
: So - the proper slug barrel is a boon to accurate slug shooting. It all depends on what you want or will be satisfied with.