The cluster is small and dominated by passive/quant-oriented managers (Dimensional, Strs Ohio) with no insider buying. Monitor next 13F for follow-through or reversal; the signal alone does not suggest a catalyst.
How the stock moved after the report
⚠ Clustered NEUTRAL VIEWSTOCK ABOVE ENTRY AT T+1- T+0 · Nov 6 $21.25entry
- T+1 · 3d ago +5.13%α +2.76% · $22.34
- T+3 · todayOpen
- T+5 · tomorrow Pending
- T+20 · in 25d Pending
- T+60 · in 3mo Pending
How similar events traded
Executive Summary
Four institutional investors added to their Amentum Holdings positions in Q3 2026, led by Dimensional Fund Advisors increasing by $16.2M, while Barclays trimmed its stake by $2.2M. The net $17.8M of buying is modest relative to the $5.4B market cap and lacks insider corroboration, making the signal weak.
Key Financial Metrics
Institutional Positions
Net institutional flow: $17.8M
▲ Buyers (4)
| Institution | Action | Change | Position Value | Value Δ |
|---|---|---|---|---|
| Dimensional Fund Advisors | ADD | +30.2% | $130.7M | $16.2M |
| Fifth Third Bancorp | ADD | +43.6% | $7.3M | $1.5M |
| Citigroup | ADD | +28.6% | $734.0K | $83.0K |
| Strs Ohio | ADD | +33.2% | $150.0K | $21.0K |
▼ Sellers (1)
| Institution | Action | Change | Prev Value | Value Δ |
|---|---|---|---|---|
| Barclays | TRIM | -66.5% | $3.1M | -$2.2M |
Key Facts
- 4 institutional buyers added $17.8M in aggregate during Q3 2026
- Dimensional Fund Advisors was the largest buyer, adding $16.2M to a $130.7M position
- Barclays trimmed 66.5% of its stake, selling $2.2M
- No open-market insider buying occurred during the window (confluence score 28/100)
- 13F data is 45+ days stale; positions may have changed since quarter-end
Financial Impact
Net institutional buying of $17.8M, or approximately 0.3% of market cap
Risk Factors
- 13F data is stale by 45+ days; positions may have been unwound
- No insider buying to corroborate the institutional accumulation
- Cluster size is small relative to market cap and lacks high-conviction activist or value fund participation
Market Snapshot
Investment Themes
Documents Analyzed
This report is based on 1 institutional 13F filing from SEC EDGAR.
| Document | Accession Number |
|---|---|
| INST-CLUSTER Data (Synthetic) | inst-cluster-AMTM-2026-Q3 |
Track record
18 reports on AMTM
3 of 5 bullish or bearish reports moved the stock their way by T+1. Best: +5.13% at T+1 after the Nov 5, 2026 report. 3 of 5 went positive at some point.
Filters
- Nov 6, 20265d ago Institutional Cluster Neutral 2/10 Viewing Entry $21.25 to $22.34 ▲ +5.13% +2.76% vs SPY
- Nov 5, 20267d ago GOVT-CONTRACT Bullish 5/10 Entry $21.25 to $22.34 ▲ +5.13% +2.76% vs SPY
- Oct 29, 202614d ago GOVT-CONTRACT Bullish 5/10 Entry $21.87 to $22.47 ▲ +2.74% +3.22% vs SPY
- Oct 29, 202614d ago GOVT-CONTRACT Neutral 2/10 Entry $21.87 to $22.47 ▲ +2.74% +3.22% vs SPY
- Oct 27, 202616d ago GOVT-CONTRACT Neutral 3/10 Entry $21.69 to $22.07 ▲ +1.75% +2.13% vs SPY
- Oct 23, 202620d ago GOVT-CONTRACT Neutral 3/10 Entry $22.07 to $21.75 ▼ −1.45% −2.01% vs SPY
- Sep 30, 20266w ago GOVT-CONTRACT Neutral 3/10 Entry $18.48 to $18.14 ▼ −1.84% −2.58% vs SPY
- Sep 29, 20266w ago GOVT-CONTRACT Neutral 4/10 Entry $18.12 to $18.48 ▲ +1.99% +1.81% vs SPY
- Sep 22, 20267w ago GOVT-CONTRACT Neutral 3/10 Entry $19.71 to $19.40 ▼ −1.57% −1.49% vs SPY
- Sep 18, 20267w ago GOVT-CONTRACT Neutral 3/10 Entry $19.90 to $19.70 ▼ −1.00% −0.99% vs SPY
US Market Status
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