I have messed around with both Gallery Practice Rifles (GPR) and with Stevens-Popes (SP) for a few years now.  Here's how I look at them:

The SP was made as a barrel only (and maybe it came with a front sight), And was D&T for the Krag rear sight of any type.  When you buy (big bucks) a complete SP Krag, you are buying a SP barrel and it better be at least shootable.  The rest of the rifle really has no more value than a complete collection of parts.

To me, if you can't get an original SP barrel to shoot (and they are worth a lot of bronze brush & JB work), then you have something that is probably worth a lot less than you just paid. 

I would be very skeptical about lining, simply because the exterior of the barrel is NOT concentric with the bore.  To me, that is a job for a skilled machinist who knows what the problem is BEFORE he puts the barrel on his lathe.   John Taylor is the first guy I would call. 

If a SP Krag that had been relined came around, I don't think I'd chance more than 60 % of the value of a good one.  They just ain't the same.

The GPRs were made about 1908-09.  The two I have handled were not as smooth in operation as a regular Krag.  Maybe they were not heat-treated, since they were .22 rimfires only, not .30-40s.  The first production run were chambered for .22 Extra Long and have groove diameters of about 0.226" and 18" twist rifling.  They will shoot .22 Long Rifles safely, but accuracy is minimal.  IMHO, this bunch are over-priced curios.

The later production GPRs were fitted with barrels that were correct for .22 Long Rifle cartridges.  They shoot pretty well, but a real slick Krag they ain't.  Others think they are worth as much as a good SP Krag.  I don't.