To Final Finish or Not

If you have to do something, use KG2 with about 100 strokes just in the throat/lead area and shoot it.
I have never seen a throat area that did not have small tooling marks, but most barrels shoot great without addressing them.
I would run a dry patch down the barrel and shoot it as is.
I will only use FF in a factory barrel or in a barrel that has "cracking" in the throat area. Your mileage may vary.
 
Do you need to ff? If not then don’t.

Now read that again.

Unless you have discovered a reason to use a last resort then it’s generally advised to not go nuclear. If you struggle to get a load to perform and are going to scrap the barrel then maybe give it a shot. But on a lovely new bore let it live in peace.
 
I bought the ff system for a dpms lr308- factory barrel. After shooting some hornady match and fgmm through it, I left the ff in the box. Maybe if precision falls off, but in a 308 that will be a while. On a custom barrel? No way, at least not before finding a good reason.
 
I used it on a factory .243 Win RPR barrel that had just over 1,000rds through it and the groups were starting to open up. There was some serious fire cracking in the throat and after running 3rds each of the finest grades (9rds total) through it and a thorough clean, it was back to shooting 1/2moa groups. I think it helped smooth the throat to keep it from ripping chunks of copper off the bullet jackets.

Worked for me, but keep in mind it was a factory barrel that was nearly shot out, didn't have much to lose.

Would I use this on a custom barrel? Absolutely not.
 
Don't use Final Finish on that barrel. If anything use the TMS rounds. You can use them as a break in with 3 rounds, clean and then 3 more and clean and done and then a couple every 250-300 rounds to keep throat smooth.
 
Shilen barrels are hand-lapped. After chambering, they need the throat lapped, unless the lapping was done after the chambering. TMS or FF bullets from the specified portion of the FF box (per Tubb's instructions) will accomplish that. If the rifle shoots better than you ever dreamed, don't do anything except shoot it.
 
I've never use the TMS on a hand lapped barrel. I did use 5 of them to break in a factory Savage 22/250. The gun shot very well, better than most of my custom barrels. I used the FF system on a factory .243 barrel that had run some hot varmint loads for 1200 rounds. It didn't do anything to save it. I don't really think it will make much difference either way in a quality barrel.