Before I ventured into a liner or a new barrel, I would want to know about the firing pin, its diameter, protrusion and how well it might work with modern primers.  Then I would look at the trigger.  Can it be adjusted safely?   

For me, unless it can be made to shoot safe smokeless loads with reasonable accuracy, I would leave it as is.  I have a Gahendra and a 1902 roller I'm thinking about.   

The Gahendra is nominally a .577/450, but the groove diameter is about .458 at the breech and at the muzzle, but about .452 in the middle.  Trigger pull was quite a lot.  12-15 lbs?   

The 1902 roller is nominally a 7x57, groove diameter about .284 at breech and muzzle, but the slug was in free-fall for about 6 inches someplace in the middle.  Again, trigger pull is heavy.

My thinking is that the Gahendra might make a nice .38 Special, the roller a .30-30, but just now, I'm not about to throw money at either.

I plan some 577 though it even if its round balls. the questions are mostly to occupy my mind waiting.  god only knows when it will show up.

Keep in Mind the Sniders from IMA can included minor  British parts, but are mostly Nepalese made.  Read IMA's description and expect to receive just exactly what they describe. You might get better. But it is unlikely you will get worse.

Snider is the conversion of a black powder muzzle loader. All the cautions that go with that apply.

Reformed 24 gauge CBC brass works well unless the chamber is oval shaped-common in the Nepalese made barrels.. Brass cases get distorted and become difficult to extract.  Plastic 24 gauge shells work however-if you can find them.  

I  believe John Taylor has chamber lined and rechambered at least one of these, maybe more.

It is a post civil war era cartridge.  The fellows over British Militaria (especially the Canadians) have extensive experience shooting these guns. They can tell you what works.  But keep in  Mind there are British guns and all others.

It is not  good candidate for conversion. Certainly try and let us know how it works.  If it works.  Locking mechanism is not all that strong.  Extraction will be an issue.

My particular Snider was hand selected from the top of a pallet in IMA's ware house in 2011. I selected it.  The lock is  a Tower dated 1847. The barrel and action are not marked, but they are better quality than others seen in that ware house that day.  We shot that gun, that day and it shot okay.  I bought that gun. I cleaned it up and put in the storage locker where it has sat ever since.  It is the only Snider I own.  I had a Lord carbine and sold it.

Early one Screw Gahendra's have a constriction in the barrel. The barrels for the singles screws guns are mandrel wound forged and bores are tapered.  The stock tenon is silver brazed on the bottom of the barrel and the barrel at that point collapsed and caused a slight constriction.  Early on  when these guns were first released the were reports of these early guns having a history bursting barrels.  I have never seen  the document supporting that , nor have I seen any contemporary reports of barrels bursting.

The later 2 screw Gahendra's appear to have solid barrels and the two I have checked do not have a bore constriction. One of those two screw guns is mine.

The early  one  screw models appear heavily hand made and hand fitted.  Parts interchangeability lacking, repairs require lots of hand fitting.  

The action is interesting, and would  be a tinkerer's dream, if you have the tools and skill to do such work-especially springs.

I have a 1902 that's now a 38-55. If I was going to do another one, I think I would consider a 32-40.

Tom, that's a very nice Snider you have.

Does anyone remember his Kipling? Is he now politically uncorrect?  Sniders were "cripple-stoppers".

Tom, that is one heck of a beautiful Snider.

well, I got it now.  It looks nice probably because they buffed with in a inch of its life   .  If you're reading this you are probably part of the problem you all are a bad influence. I was moved to also buy a British Snyder waiting on shipping info.