Depends on several factors.
This 6.5x47 on a Pierce action, Broughton barrel and McMillan Rem Sporter took about 4 months for the parts to be accumulated and about 2-3 days for Chris Matthews of
http://longshotriflesllc.com/ to build.
This 6.5x47 on a Surgeon action, Kreiger barrel and AICS stock took me about 2 weeks to accumulate the parts. Brownells typically keeps the actions in stock. The barrel was on hand at Kreiger as the original owner decided not to buy it and the AICS stock was also in stock from Mile High Shooters in Colo. Once Chris received the barrel on Saturday, the last component he received, he emailed me on Tuesday morning to let me know it was done.
My Pre 64 M70 in 9.3x62 took about 6 months total. Pacnor barrel took about 12 weeks to receive. The D'Arcy Echols stock was delivered in a week from D'Arcy and the action was received in about a week as well. Between Redneck doing his magic on the metal and initial inletting and CASII (Charley Santoni) finsihing it all up ran another 2+ months.
Now, this is where it can get ridiculously long......probably around 4 years.
Each and every 'smith has ups and downs. Some, who are very well known and great at what they do, like great doctors, will require longer waits. Chris Matthews is well known and very good but I learned that if "I" accumulated all the components I can get him to build my rifle/s VERY fast. If you turn everything over to the 'smith in question, he/she will likely do it in conjunction with all the other projects they work on on a daily basis.
Alan