I met with one of the high-ups of a "catholic index fund" advisor and was told that the below exclusion would apply to any manufacturer of firearms, even of small arms for personal and family defense.  Since self-defense is a right and even grave duty under our Catechism, and the Second Amendment derives from Catholic teaching on tyrannicide, and even war can be justified under Catholic Just War Doctrine, this blanket prohibition didn't seem very Catholic to me.  I mentioned that many of my Catholic clients are pro-gun and would strongly disagree with this prohibition, and the reply I got was that the fund deals mainly with institutional investors, so it seemed the concerns of individual Catholics were not too relevant.

If you google the "Ecclesial Advisor" for the fund, Fr. Seamus P. Finn, you will find he is a "social justice" advocate ("Director of Justice/Peace and Integrity of Creation"), a proponent of IMF governance reform, and linked with Soros-type marxists and leftists (see for example here, here, here, here, and apparently if you have a password you can chat with Seamus about IMF Governance Reform on a ning page here.)

This is the offending investment prohibition:

InvestingForCatholics.com • a division of Index Funds Advisors.

Companies that earn at least 20% of their total business revenue through the production and/or sale of military weapons and/or weapons of mass destruction