Don't confuse the "plan documents" (aka the terms of service written by the bankers with their hands in your pocket) with the IRS regs. Some plans do allow in-service rollovers, and to be sure, you should make a request in writing.
When rolling over money, have the money sent directly to the other retirement account. If the check comes to you first, then the payer has to withhold 20%, which you won't get back until after you file your taxes and prove the funds were in fact rolled over. And, of course, you would need to 'front' that 20% in order to get the whole amount rolled!
Having done this four times, in each case the people managing the 401k sent me the check made out to my IRA's bank, with the notation FBO me, aka "For The Benefit Of" and each case my bank cashes the check and transfers the proceeds into my IRA.
Don't confuse the "plan documents" (aka the terms of service written by the bankers with their hands in your pocket) with the IRS regs. Some plans do allow in-service rollovers, and to be sure, you should make a request in writing.
When rolling over money, have the money sent directly to the other retirement account. If the check comes to you first, then the payer has to withhold 20%, which you won't get back until after you file your taxes and prove the funds were in fact rolled over. And, of course, you would need to 'front' that 20% in order to get the whole amount rolled!