desert tactical arms

Can anyone recommend a good machine shop or gunsmith around Tulsa to do some barrel rethreading? I have (3) Desert Tech barrels that have 3/4-24 threads and I need to have them downsized to 5/8-24. Any input would be greatly appreciated.

My latest purchase is a Desert Tech SRS (Stealth Recon Scout) sniper system. This is a switch barrel system and it takes 90s or less to change from one caliber to the next. Pictured is the .308 barrel (installed), the 6.5 Creedmoor barrel, .300 Winchester magnum conversion kit, and the .338...