Why do you say "Bubba"? Bubba is when someone who {thinks} that they are a gunsmith ruins a perfectly good C&R. I have a truly Bubba'd K-98 Mauser that I bought for $75 and it is a GROSS attempt at sporterizing, for details, please PM me.
So is this to say that you cannot replace the barrel if needed, or stock if needed or replace parts if needed? Why would a scope be a no-no? Also, what is the difference just because someone bought it with a C&R versus someone who could buy the exact same kind of gun in a gunshop on a shelf or from a private owner? I've been to many forums and never heard of this.
Also, if the rifle was made prior to 1899 it excuses it from ANY FFL.
Pre-1899 Firearms FAQ About half way down the page you will find a paragraph about Mosin's.
If there is a doubt to the date of manufacturer you can usually find it under the tang which requires disassembly. My Finn captured M-39 falls in this category and is heavily altered but still very serviceable. My Swedish Mauser 6.5x55mm Carbine falls in this category as well. Also, here is another handy link:
7.62x54r.net The now late friend I got the M-39 from bought it from a man with a C&R and he altered it to suit him. I changed out the ATI bolt handle and replaced it with a straight bolt handle because the torque needed to lift the bolt after firing required a HICKORY rough cut 2x6 and a "B.F.H."! My M-39 has an ATI stock, Rock Monut Bi-Pod, nylon padded sling, and aftermarket sights and is exceptionally accurate with a .310" bore and a 26" long Finn barrel of said bore size. The Finn's made the barrels to not only fire their own ammo which they sized at 7.62x53 but kept the longer throat design, rimmed ammo headspaces on the rim not the shoulder, but also any Russian ammo they may encounter on the battlefield, even the high pressured machine gun ammo made in Russia as well.
Besides, who is really going to check up on you on a regular basis to see if you added an era correct optic and mount on a C&R weapon? Does the FCC knock on every door for illegal HAM radios everyday? I seriously believe if you did it tastefully and tried to keep it era correct I doubt they would tar and feather you. I also do believe that Seastalkingbear can attest to this statement as well.
My M-39 started life as a Sestroryetsk M-91 {not M-91-30} made in Russia and falls in the Pre-1899 exemptions. And is a Sako rework as well.
I plan on altering my M-1 Garand but in good taste. Different barrel in same caliber, not that .308 stuff and keeping it looking "stock" or within factory parameters. PM me for details as well if you have any doubts.
Also, please read my Public Profile under "Additional Information" as well. I used to Moderate in about 7 forums and was not only a "Roving Topic Moderator", but I was also a Military Surplus specific Moderator as well, along with my military time.
With all due respect. GarandGuy