“This is the first time in my 30 years’ experience that I’ve seen managers make bets like that with their funds,” Cargile said.

Bill Gross at PIMCO Total Return Fund has had some ill-timed trades on Treasuries this year.

Mutual funds added $108 billion to taxable bond funds year-to-date while $63 billion was pulled out of equity funds.

Vanguard Total Bond Market ETF (NYSEArca: BND)

Max Chen contributed to this article.