Greetings. I'm new to this forum and am hoping someone on here might be able to help me out with some information. I recently acquired a H&H 360 miniature express rifle, which was made in 1877. It is a project gun due to the fact that at some point in the the rifle's life someone took a square end reamer and lengthened the chamber by roughly 1/2". I can only guess as to why someone might have done that, but I would say that someone did it in the attempt to chamber more common 9.3x74 ammo. Regardless, I would like to bring this back to original chamber specs, which I think my only option is to do a full barrel reline (other opinions welcome on that point).

I know I can get a 9.3mm (.366 groove dia.) liner made. My question to others on this forum is what would be a good twist rate. I measured the twist in my rifle, and was surprised to find it measured 1-46, which was much slower than I was expecting to find. On another forum an owner of a German rifle in 9.3mm-57R relayed that his twist rate was 1-15, and was very accurate with a 200 gr bullet. I am hoping others on this forum might have British made 360 BPE rifles and could tell me what their twist rates are. It seems to me a faster twist rate would be more versatile with the 190-210 gr bullets that this cartridge was also loaded with. Since the originality of this rifle has already been compromised with the messed with chamber, having the barrel relined with a more optimum twist rate won't keep me up at night. I look forward to your suggestions