In my personel view, three days, even if the guy lets you shoot it (he probably won't) doesn't prove squat with a single trigger. English single trigger designs, also, my personel view, are among the very worst. You don't say if the Lang is a boxlock (slightly better single trigger) or a sidelock (wood performs the central support role, and, while it was likely OK, back when the gun was new, it might not be now-usually not, in my experience).
Think this through a bit more. I'm pretty sure every part for a 21 trigger is available off the shelf. I'm not a fan of that trigger, either, but, at least there will be a bit less suspense when it acts up.
Best,
Ted
