ACK Asset Management LLC

Hedge Fund • Long/Short

ACK Asset Management LLC is a Long/Short Hedge Fund based in Greenwich, CT led by John Henry Reilly, reporting $949.1M in AUM as of Q3 2025 with 58% Industrials concentration and 63% concentrated in top 10 holdings.

Managing PartnerJohn Henry Reilly

Portfolio Value: $839.5M
Positions: 21
Top Holding: ENS at 7.86%
Last Reported: Q3 2025

Address777 West Putnam Ave., Suite 300, Greenwich, CT, 06830, United States

Top Holdings

Largest long holdings in ACK Asset Management LLC's portfolio (62.7% of total portfolio)

See all holdings

GthenH

Holding	Sector	Position	Weight	Traded	Ownership	Owned Since
1 EnerSys ENS	Electrical Equipment & Parts Industrials	$66.0M	7.86%	—	1.56% 584.3K shares	Q1 2018 Held for 7y 8m
2 Materion MTRN	Industrial Materials Basic Materials	$63.4M	7.55%	—	2.53% 524.8K shares	Q1 2020 Held for 5y 8m
3 Granite Construction GVA	Engineering & Construction Industrials	$59.8M	7.12%	—	1.24% 545.0K shares	Q2 2024 Held for 1y 5m
4 Astronics ATRO	Aerospace & Defense Industrials	$56.1M	6.68%	-$37.9M Sold	3.47% 1.2M shares	Q4 2022 Held for 2y 11m
5 Advanced Drainage Systems WMS	Construction Industrials	$54.1M	6.44%	+$6.2M Bought	0.50% 390.0K shares	Q2 2025 Held for 5 months
6 JBT Marel Corporation JBTM	Unknown Unknown	$49.2M	5.86%	—	0.67% 350.5K shares	Q4 2024 Held for 11 months
7 Core & Main CNM	Industrial - Distribution Industrials	$48.4M	5.77%	+$48.4M Bought	0.47% 900.0K shares	Q3 2025 Held for 2 months
8 ATS Corporation ATS	Industrial - Machinery Industrials	$48.4M	5.76%	—	1.91% 1.8M shares	Q4 2022 Held for 2y 11m
9 Albany International Inc. AIN	Apparel - Manufacturers Consumer Cyclical	$40.5M	4.83%	+$9.3M Bought	2.58% 760.0K shares	Q2 2025 Held for 5 months
10 JHX James Hardie Industries plc JHX	Unknown Unknown	$40.3M	4.81%	+$40.3M New	0.36% 2.1M shares	Q3 2025 Held for 2 months

See all holdings

GthenH

Changes

Portfolio activity, position movements, and quarter-over-quarter changes in ACK Asset Management LLC's latest filing

See all changes

GthenC

Market Value

$839.5M

Prior: $761.4M

Q/Q Change

+10.25%

+$78.0M

Net Flows % of MV

-19.29%

Turnover Ratio

36.09%

New Purchases

3 stocks

$111.5M

Added To

5 stocks

+$23.7M

Sold Out Of

8 stocks

$245.4M

Reduced Holdings

2 stocks

-$51.8M

Increased Positions

Position	Shares Δ	Change
1 JHX James Hardie Industries plc JHX	New	0 → 2.1M +$40.3M
2 JHX James Hardie Industries JHX	New	0 → 2.1M +$40.3M
3 Apogee Enterprises APOG	New	0 → 708.0K +$30.8M
4 Albany International Inc. AIN	+29.91%	585.0K → 760.0K +$9.3M
5 NPK International NPKI	+28.53%	1.2M → 1.6M +$4.0M

Decreased Positions

Position	Shares Δ	Change
1 Dycom Industries DY	Sold	224.7K → 0 −$54.9M
2 MYR Group MYRG	Sold	265.2K → 0 −$48.1M
3 Regal Rexnord RRX	Sold	275.0K → 0 −$39.9M
4 MRC Global MRC	Sold	2.3M → 0 −$31.1M
5 Mirion Technologies MIR	Sold	1.3M → 0 −$28.8M