FRONTIER CAPITAL MANAGEMENT CO LLC reported AMENTUM HOLDINGS INC (AMTM) in 4 quarterly 13F filings from 2025 Q1 through 2025 Q4. Peak portfolio weight reached 1.78% in 2025 Q4. The latest visible filing shows AMTM at 1.78% of the fund.
This page tracks quarterly shares, estimated market value, portfolio weight, filing dates, and disclosure-aligned stock prices directly from SEC EDGAR 13F filings.
This page is designed to answer the real investor question behind a 13F filing: how meaningful was FRONTIER CAPITAL MANAGEMENT CO LLC's position in AMENTUM HOLDINGS INC, and how did that conviction change over time? You can read the holding window, peak weight, latest reported size, disclosure timing, and quarter-by-quarter changes without piecing the story together from raw SEC rows.
AMTM was reported at 1.78% of portfolio in the most recent visible filing.
Peak weight helps separate a token disclosure from a real conviction holding the fund genuinely cared about.
Longer holding windows often tell a very different story from short-lived tactical trades or one-quarter experiments.
Knowing that a fund owned a stock is useful. Knowing whether it was a 0.20% placeholder or a true high-conviction position is where the signal actually starts.
As of 2026 Q1 β sorted by position size
These are the practical questions this page is built to answer before you even open the full history table.
FRONTIER CAPITAL MANAGEMENT CO LLC reported AMTM across 4 quarterly 13F filings, from 2025 Q1 through 2025 Q4.
The largest reported portfolio weight for AMTM was 1.78% in 2025 Q4.
The most recent filing on this page is 2025 Q4, when FRONTIER CAPITAL MANAGEMENT CO LLC reported 5,772,976 shares, equal to 1.78% of portfolio, with an estimated market value of $167.4M.
The chart compares FRONTIER CAPITAL MANAGEMENT CO LLC's quarterly AMTM portfolio weight with the stock's indexed share price, so you can see whether the fund was building, trimming, or holding the position as price moved.