I’m looking at building cost-effective. Custom 6.5 PRC. I’m wanting to use the t3x lite as the base. I’m wanting to get the stock Tikka T3X Lite factory sporter Barrel cut from 24 in down to 18 in and then re-crowned and threaded by very good gunsmith. Is there any issues to worry about with accuracy or ruining the barrel other than obvious loss of velocity?
No you should be fine accuracy wise and long as you have a good crown put back on the barrel but honestly it would probably be easier to just buy a prefit and thread it on then if you ever wanted to swap back to the 24” you could. And it probably wouldn’t be much more expensive.
Thank you for the information. I wish I could do a proof carbon barrel. But a drop in for a Tikka is like $900 and they do not make one in 6.5 PRC that is 18". So if I get the t3x lite 6.5 PRC on sale. After paying the gunsmith it will only be a total of less than $800. Then I can upgrade the stock later. Blasted budgets 
. I wish I could buy one of the solace aero precision actions / trigger tech they’re on sale for like $800 right now!!!
You could go with a preferred barrel and if you don’t ad fluting or barrel coating it’s only like $580 for a threaded prefit. Even if you flute it and coat it you would still be under $800.
I had my lgs cut a T3x superlite 6.5 creedMoor down as far as they would bc of the fluting and they threaded it 1/2-28. I think it’s about 21 or 22” now. It shoots really well. I have a 143 eld x load that it likes and then it likes the hsm sierra game king. On the other hand I had a T3x lite in 300 wsm. I had them just cut it down to about 18” and they threaded it 1/2-28. I couldn’t get it to shoot very well but I think that was me. It was light and kicked a lot even though I was getting low SDs on the hand loads.