What you're wanting to do is an excellent planning strategy.  And, as long as your income is not below the range the law set for savings on a Marketplace insurance plan, it may work for you.

Here are the Marketplace ranges to see how Federal Poverty Levels are used to determine eligibility for reduced-cost health coverage:

• Income between 100% and 400% FPL: If your income is in this range, in all states you qualify for premium tax credits that lower your monthly premium for a Marketplace health insurance plan.
• Income below 138% FPL: If your income is below 138% FPL and your state has expanded Medicaid coverage, you qualify for Medicaid based only on your income.
• Income below 100% FPL: If your income falls below 100% FPL and your state hasn't expanded Medicaid coverage, you won't qualify for either income-based Medicaid or savings on a Marketplace health insurance plan. You may still qualify for Medicaid under your state's current rules.

Also, for ACA you need to look at your Modified Adjusted Gross Income.  The Marketplace definition of MAGI is adjusted gross income (AGI) plus these:  untaxed foreign income, non-taxable Social Security benefits, and tax-exempt interest.  

If you make a Traditional IRA contribution and reduce your MAGI below 100% of the FPL you will not be eligible for ACA.  And if your income is below 138% FPL, then you are exempt from any penalty for not having insurance coverage if you live in a state that does not offer Medicaid.

For 2017 and 2018, your total contributions to all of your traditional and Roth IRAs cannot be more than:

• $5,500 ($6,500 if you’re age 50 or older), or
• your taxable compensation for the year, if your compensation was less than this dollar limit

See the TurboTax article What Is the Difference Between AGI and MAGI on Your Taxes? for more information.

[Edited 2.7.18 | 2:47 PM]