I agree with Peter that all of these variables do exist. However, replacement barrels have been made before and there's no reason they can't be made here in the USAas they already are by Armalon and Lothar Walther overseas. The short chamber issue has been addressed and photos posted of a similar setup on a .30-40 Krag barrel as made by Criterion. If a barrel won't index without skimming the shoulder then so be it. It's been done forever with other barrels. No big deal. If the barrel is too loose, then a breeching washer is the fix as Peter says. They've also been a tried and true method in the SLR and as well as many other rifles including some of the Enfield 7.62 conversions. RH vs LH twist? There's nothing new about that either when it comes to the No.4. Savage used it early in production and Long Branch late in production. I sent Criterion a No.4 body in good shape this week stripped of it original barrel so they can move into design and production taking into consideration all of the points being discussed here. I'll be looking forward to a test trial of one of their first batch of new No.4 barrels.