SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934 (Amendment No. 51)

Aerojet Rocketdyne Holdings, Inc.

(previously filed under GenCorp Inc.)

(Name of Issuer)

Common Stock, $0.10 Par Value Per Share

(Title of Class of Securities)

___________________007800105___________________

David Goldman

GAMCO Investors, Inc.

One Corporate Center

Rye, New York 10580-1435

(914) 921-5000

 (Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

______________________August 5, 2015________________________

(Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box  .

---

CUSIP No. 007800105

 

---

 

CUSIP No. 007800105

 

---

 

CUSIP No. 007800105

 

---

 

CUSIP No. 007800105

---

CUSIP No. 007800105

---

CUSIP No. 007800105

---

This Amendment No. 51 to Schedule 13D on the Common Stock of Aerojet Rocketdyne Holdings, Inc. (previously filed under GenCorp Inc.) (the "Issuer") is being filed on behalf of the undersigned to amend the Schedule 13D, as amended (the "Schedule 13D") which was originally filed on November 30, 1988.  Unless otherwise indicated, all capitalized terms used herein but not defined herein shall have the same meanings as set forth in the Schedule 13D.

Item 2 to Schedule 13D is amended, in pertinent part, as follows:

This statement is being filed by Mario J. Gabelli ("Mario Gabelli") and various entities which he

directly or indirectly controls or for which he acts as chief investment officer.  These entities engage in various aspects of the securities business, primarily as investment adviser to various institutional and individual clients, including registered investment companies and pension plans, and as general partner or the equivalent of various private investment partnerships or private funds.  Certain of these entities may also make investments for their own accounts.

The foregoing persons in the aggregate often own beneficially more than 5% of a class of equity securities of a particular issuer.  Although several of the foregoing persons are treated as institutional investors for purposes of reporting their beneficial ownership on the short-form Schedule 13G, the holdings of those who do not qualify as institutional investors may exceed the 1% threshold presented for filing on Schedule 13G or implementation of their investment philosophy may from time to time require action which could be viewed as not completely passive.  In order to avoid any question as to whether their beneficial ownership is being reported on the proper form and in order to provide greater investment flexibility and administrative uniformity, these persons have decided to file their beneficial ownership reports on the more detailed Schedule 13D form rather than on the short-form Schedule 13G and thereby to provide more expansive disclosure than may be necessary.

(a), (b) and (c) - This statement is being filed by one or more of the following persons: GGCP, Inc.  ("GGCP"), GGCP Holdings LLC ("GGCP Holdings"), GAMCO Investors, Inc. ("GBL"), Gabelli Funds, LLC ("Gabelli Funds"), GAMCO Asset Management Inc. ("GAMCO"), Teton Advisors, Inc. ("Teton Advisors"), Gabelli Securities, Inc. ("GSI"), G.research, LLC ("G.research"), MJG Associates, Inc. ("MJG Associates"), Gabelli Foundation, Inc. ("Foundation"), MJG-IV Limited Partnership ("MJG-IV"), and Mario Gabelli.  Those of the foregoing persons signing this Schedule 13D are hereinafter referred to as the "Reporting Persons".

GGCP makes investments for its own account and is the manager and a member of GGCP Holdings which is the controlling shareholder of GBL.  GBL, a public company listed on the New York Stock Exchange, is the parent company for a variety of companies engaged in the securities business, including those named below.

GAMCO, a wholly-owned subsidiary of GBL, is an investment adviser registered under the Investment Advisers Act of 1940, as amended ("Advisers Act").  GAMCO is an investment manager providing discretionary managed account services for employee benefit plans, private investors, endowments, foundations and others.

GSI, a majority-owned subsidiary of GBL, is an investment adviser registered under the Advisers Act and serves as a general partner or investment manager to limited partnerships and offshore investment companies and other accounts.  As a part of its business, GSI may purchase or sell securities for its own account.  GSI is a general partner or investment manager of a number of funds or partnerships, including Gabelli Associates Fund, L.P., Gabelli Associates Fund II, L.P., Gabelli Associates Limited, Gabelli Associates Limited II E, ALCE Partners, L.P., Gabelli Capital Structure Arbitrage Fund LP, Gabelli Capital Structure Arbitrage Fund Limited, Gabelli Intermediate Credit Fund L.P., Gabelli Japanese Value Partners L.P., GAMA Select Energy + L.P., GAMCO Medical Opportunities L.P., GAMCO Long/Short Equity Fund, L.P., Gabelli Multimedia Partners, L.P, Gabelli International Gold Fund Limited and Gabelli Green Long/Short Fund, L.P.

G.research, a wholly-owned subsidiary of GSI, is a broker-dealer registered under the Securities Exchange Act of 1934, as amended ("1934 Act"), which as a part of its business regularly purchases and sells securities for its own account.

Gabelli Funds, a wholly owned subsidiary of GBL, is a limited liability company. Gabelli Funds is an investment adviser registered under the Advisers Act which provides advisory services for The Gabelli Equity Trust Inc., The Gabelli Asset Fund, The GAMCO Growth Fund, The Gabelli Convertible and Income Securities Fund Inc., The Gabelli Value 25 Fund Inc., The Gabelli Small Cap Growth Fund, The Gabelli Equity Income Fund, The Gabelli ABC Fund, The GAMCO Global Telecommunications Fund, The Gabelli Gold Fund, Inc., The Gabelli Multimedia Trust Inc., The Gabelli Global Rising Income & Dividend Fund, The Gabelli Capital Asset Fund, The GAMCO International Growth Fund, Inc., The GAMCO Global Growth Fund, The Gabelli Utility Trust, The GAMCO Global Opportunity Fund, The Gabelli Utilities Fund, The Gabelli Dividend Growth Fund, The GAMCO Mathers Fund, The Gabelli Focus Five Fund, The Comstock Capital Value Fund, The Gabelli Dividend and Income Trust, The Gabelli Global Utility & Income Trust, The GAMCO Global Gold, Natural Resources, & Income Trust, The GAMCO Natural Resources Gold & Income Trust, The GDL Fund, Gabelli Enterprise Mergers & Acquisitions Fund, The Gabelli SRI Fund, Inc., The Gabelli Healthcare & Wellness ^Rx Trust, The Gabelli Global Small and Mid Cap Value Trust and Gabelli Value Plus+ Trust (collectively, the "Funds"), which are registered investment companies.  Gabelli Funds is also the investment adviser to The GAMCO International SICAV (sub-funds GAMCO Merger Arbitrage and GAMCO All Cap Value), a UCITS III vehicle.

Teton Advisors, an investment adviser registered under the Advisers Act, provides discretionary advisory services to The TETON Westwood Mighty Mites^sm Fund, The TETON Westwood Income Fund, The TETON Westwood SmallCap Equity Fund, and The TETON Westwood Mid-Cap Equity Fund.

MJG Associates provides advisory services to private investment partnerships and offshore funds.  Mario Gabelli is the sole shareholder, director and employee of MJG Associates.   MJG Associates is the Investment Manager of Gabelli International Limited and Gabelli Fund, LDC.  Mario J. Gabelli is the general partner of Gabelli Performance Partnership, LP.

The Foundation is a private foundation.  Mario Gabelli is the Chairman, a Trustee and the Investment Manager of the Foundation. Elisa M. Wilson is the President of the Foundation.

Mario Gabelli is the controlling stockholder, Chief Executive Officer and a director of GGCP and Chairman and Chief Executive Officer of GBL.  Mario Gabelli is also a member of GGCP Holdings. Mario Gabelli is the controlling shareholder of Teton.

                             MJG-IV is a family partnership in which Mario Gabelli is the general partner.  Mario Gabelli has less than a 100% interest in MJG-IV.  MJG-IV makes investments for its own account.  Mario Gabelli disclaims ownership of the securities held by MJG-IV beyond his pecuniary interest.

The Reporting Persons do not admit that they constitute a group.

GAMCO and G.research are New York corporations and GBL, GSI, and Teton Advisors are Delaware corporations, each having its principal business office at One Corporate Center, Rye, New York 10580. GGCP is a Wyoming corporation having its principal business office at 140 Greenwich Avenue, Greenwich, CT 06830.   GGCP Holdings is a Delaware limited liability corporation having its principal business office at 140 Greenwich Avenue, Greenwich, CT 06830.  Gabelli Funds is a New York limited liability company having its principal business office at One Corporate Center, Rye, New York 10580.  MJG Associates is a Connecticut corporation having its principal business office at 140 Greenwich Avenue, Greenwich, CT 06830.  The Foundation is a Nevada corporation having its principal offices at 165 West Liberty Street, Reno, Nevada 89501.

For information required by instruction C to Schedule 13D with respect to the executive officers and directors of the foregoing entities and other related persons (collectively, "Covered Persons"), reference is made to Schedule I annexed hereto and incorporated herein by reference.

(d) – Not applicable.

(e) – Not applicable.

Item 5 to Schedule 13D is amended, in pertinent part, as follows:

               (a) The aggregate number of Securities to which this Schedule 13D relates is 9,243,916 shares, representing 14.60% of the 63,316,612 shares outstanding. This latter number of shares is arrived at by adding the number of shares reported in the Issuer's most recently filed Form 10-Q for the quarterly period ended May 31, 2015 (63.0 million) to the number of shares which would be receivable by the Reporting Persons if they were to convert all of the Issuer's 4.0625% Convertible Subordinated Debentures held by them into the Common Stock of the Issuer (316,612 shares).  The Reporting Persons beneficially owned those Securities as follows:

Mario Gabelli is deemed to have beneficial ownership of the Securities owned beneficially by each of the foregoing persons.  GSI is deemed to have beneficial ownership of the Securities beneficially owned by G.research.  GBL and GGCP are deemed to have beneficial ownership of the Securities owned beneficially by each of the foregoing persons other than Mario Gabelli and the Foundation.

(b) Each of the Reporting Persons and Covered Persons has the sole power to vote or direct the vote and sole power to dispose or to direct the disposition of the Securities reported for it, either for its own benefit or for the benefit of its investment clients or its partners, as the case may be, except that (i) GAMCO does not have the authority to vote 340,499 of the reported shares, (ii) Gabelli Funds has sole dispositive and voting power with respect to the shares of the Issuer held by the Funds so long as the aggregate voting interest of all joint filers does not exceed 25% of their total voting interest in the Issuer and, in that event, the Proxy Voting Committee of each Fund shall respectively vote that Fund's shares, (iii) at any time, the Proxy Voting Committee of each such Fund may take and exercise in its sole discretion the entire voting power with respect to the shares held by such fund under special  circumstances such as regulatory considerations, and (iv) the power of Mario Gabelli, GBL, and GGCP is indirect with respect to Securities beneficially owned directly by other Reporting Persons.

(c) Information with respect to all transactions in the Securities which were effected during the past sixty days or since the most recent filing on Schedule 13D, whichever is less, by each of the Reporting Persons and Covered Persons is set forth on Schedule II annexed hereto and incorporated herein by reference.

(e) Not applicable.

---

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

GGCP, INC.

MARIO J. GABELLI

     Douglas R. Jamieson

     Attorney-in-Fact

TETON ADVISORS, INC.

     David Goldman

     General Counsel – Teton Advisors, Inc.

GAMCO ASSET MANAGEMENT INC.

  GAMCO INVESTORS, INC.

GABELLI FUNDS, LLC

     Douglas R. Jamieson

                    President & Chief Operating Officer – GAMCO Investors, Inc.

      President – GAMCO Asset Management Inc.

Gabelli Funds, LLC

---

Schedule I

     Information with Respect to Executive

Schedule I to Schedule 13D is amended, in pertinent part, as follows:

---

---

---

 

---

                                SCHEDULE II

                            INFORMATION WITH RESPECT TO

                 TRANSACTIONS EFFECTED DURING THE PAST SIXTY DAYS OR

                 SINCE THE MOST RECENT FILING ON SCHEDULE 13D (1)

                                   SHARES PURCHASED        AVERAGE

                        DATE            SOLD(-)             PRICE(2)

 COMMON STOCK-AEROJET ROCKETDYNE HOLDINGS, INC.

          GAMCO ASSET MANAGEMENT INC.

                       8/05/15            8,300-           22.9654

                       8/04/15              200-           23.2100

                       8/03/15            5,000-           23.2987

                       7/31/15           16,500-           23.2108

                       7/31/15              150            23.3000

                       7/30/15              700            22.6571

                       7/30/15            5,000-           22.8640

                       7/30/15            9,000-           22.8765

                       7/29/15           15,500-           23.2730

                       7/27/15            4,050-           23.0499

                       7/27/15              400            22.9916

                       7/23/15              500-           23.7258

                       7/21/15              125            23.8200

                       7/21/15              689-             *DO

                       7/21/15              250-             *DO

                       7/21/15            3,252-             *DO

                       7/21/15               63-             *DO

                       7/21/15              250-             *DO

                       7/21/15              251-             *DO

                       7/21/15              500-             *DO

                       7/17/15              300-           24.3000

                       7/16/15            1,200-           24.2100

                       7/16/15            1,000-           24.1209

                       7/15/15              900-           23.8558

                       7/15/15            4,100-           23.8432

                       7/14/15           10,000-           23.3145

                       7/14/15              300            23.3600

                       7/13/15           13,600-           22.5728

                       7/13/15              700-           22.5000

                       7/10/15            6,000-           21.1808

                       7/06/15            1,500-           20.8201

                       7/01/15           25,080-             *DO

                       7/01/15              656-             *DO

                       7/01/15              664-             *DO

                       6/30/15              300            20.7233

                       6/25/15            3,364-           21.1000

                       6/24/15              636-           21.1003

                       6/23/15            1,000-           21.3024

                       6/22/15            2,000-           21.3331

                       6/22/15            1,000-           21.3800

                       6/19/15              600            21.1400

                       6/16/15            4,500-             *DO

                       6/15/15              600            20.8499

                       6/11/15            6,000-           20.9589

                       6/09/15              600            20.1550

                       6/08/15              500            20.4600

          GABELLI FUNDS, LLC.

             GABELLI CONVERTIBLE AND INCOME SECURITIES FUND

                       7/20/15           44,437            24.2627

                       7/17/15           17,326-           24.2693

                       7/16/15           24,000-           24.2032

                       7/15/15           55,546            23.8028

             GABELLI ASSET FUND

                       7/15/15            3,000-           24.0507

CONVERTIBLE SUBORDINATED DEBENTURES -AEROJET ROCKETDYNE HOLDINGS, INC.

          GABELLI FUNDS, LLC.

             GABELLI CONVERTIBLE AND INCOME SECURITIES FUND

                       7/15/15              500-          264.4300

                       7/20/15              400-          269.5400

(1) UNLESS OTHERWISE INDICATED, ALL TRANSACTIONS WERE EFFECTED

    ON THE NYSE.

(2) PRICE EXCLUDES COMMISSION.

(*) RESULTS IN CHANGE OF DISPOSITIVE POWER AND BENEFICIAL OWNERSHIP.

14