Here are a few examples: 1. Leverage: According to Bloomberg, the $2.45 billion Mainstay Unconstrained Bond Fund is currently holding 198.4% of its assets in corporate bonds. The $28 billion Blackrock Strategic Income Opportunities Fund, the largest of the group, is currently 202% long the mortgage bond market.
http://fortune.com/2015/03/25/unconstrained-bond-funds-risk/
Unconstrained funds eliminate interest rate risk by maintaining shorter durations than core bond funds – an advantage if rates start to rise. Policymakers around the globe began “easing” five years ago by taking unprecedented measures to stabilize and induce expansion in the developed world.
https://www.forbes.com/sites/investor/2013/06/13/why-invest-in-unconstrained-bond-funds/
About PUBAX. The PIMCO Unconstrained Bond fund has gone through major changes lately, with large-scale management shifts at both the fund and firm level. For a fund with a truly go-anywhere style, investors should watch new management closely. As of August 14, 2017, the fund has assets totaling almost $3.56 billion invested in 1,260.00 different holdings.
https://money.usnews.com/funds/mutual-funds/nontraditional-bond/pimco-unconstrained-bond-fund/pubax
Morningstar notes current managers have solid pedigrees, but they have limited experience running a truly unconstrained bond fund. Also, near-term returns have not been much better than those of the broad bond market. The fund has returned 5.98 percent over the past year and 2.83 percent over the past three years.
https://money.usnews.com/funds/mutual-funds/nontraditional-bond/pimco-unconstrained-bond-fund/pubax
But of course, we tend to be willing to ignore historical facts when a more convenient promise comes along. And in this care, that promise is the rise of the unconstrained bond fund.
http://fortune.com/2015/03/25/unconstrained-bond-funds-risk/
We are willing to ignore history when a more convenient promise comes along. In this case, that promise is the rise of the unconstrained bond fund. We tend to be willing to ignore historical facts when a more convenient promise comes along.  We are willing to ignore history when a more convenient promise comes along. 
http://fortune.com/2015/03/25/unconstrained-bond-funds-risk/
Unconstrained funds have the ability to limit interest rate risk while adding alpha through diversification and access to a broad opportunity set. They can also eliminate interest rate risk by maintaining shorter durations than core bond funds – an advantage if rates start to rise.
https://www.forbes.com/sites/investor/2013/06/13/why-invest-in-unconstrained-bond-funds/
Allow us to introduce you to the Wonderful World of Unconstrained Bond Funds. The popularity of this type of fixed income fund has exploded, and it is entirely a creature of the zero interest rate percentage environment.
http://fortune.com/2015/03/25/unconstrained-bond-funds-risk/
The PIMCO Unconstrained Bond fund has gone through major changes lately, with large-scale management shifts at both the fund and firm level. For a fund with a truly go-anywhere style, investors should watch new management closely. As of January 19, 2018, the fund has assets totaling almost $3.45 billion invested in 1,243 different holdings.
https://money.usnews.com/funds/mutual-funds/nontraditional-bond/pimco-unconstrained-bond-fund/pubax
See PIMCO Unconstrained Bond Fund (PUBAX) mutual fund ratings from all the top fund analysts in one place. See PIMCO Unconstrained Bond Fund performance, holdings, fees, risk and other data from Morningstar, S&P, and others.
https://money.usnews.com/funds/mutual-funds/nontraditional-bond/pimco-unconstrained-bond-fund/pubax
what are unconstrained funds
Unconstrained funds are the funds that have the ability to limit interest rate risk while adding alpha through diversification and access to a broad opportunity set.