UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

SCHEDULE 13G

Under the Securities Exchange Act of 1934

(Amendment No. 22)*

GenCorp Inc.

(Name of Issuer)

Common Stock, $0.10 par value

(Title of Class of Securities)

368682 10 0

(CUSIP Number)

December 31, 2012

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

x Rule 13d-1(b)

¨ Rule 13d-1(c)

¨ Rule 13d-1(d)

* The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

CUSIP No.  368682 10 0

SCHEDULE 13G

(1)	Names of Reporting Persons. GenCorp Retirement Savings Plan
(2)	Check the Appropriate Box if a Member of a Group (See Instructions) (a)  ¨        (b)  ¨
(3)	SEC Use Only
(4)	Citizenship or Place of Organization Ohio
Number of Shares Beneficially Owned by Each Reporting Person With:		(5)	Sole Voting Power 0
		(6)	Shared Voting Power 3,204,262
		(7)	Sole Dispositive Power 0
		(8)	Shared Dispositive Power 3,204,262
(9)	Aggregate Amount Beneficially Owned by Each Reporting Person 3,204,262
(10)	Check Box if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions)  ¨
(11)	Percent of Class Represented by Amount in Row (9) 5.3%
(12)	Type of Reporting Person (See Instructions) EP

SCHEDULE 13G

Item 1.
	(a)	Name of Issuer:
		GenCorp Inc.
	(b)	Address of Issuer’s Principal Executive Offices:
		2001 Aerojet Road
		Rancho Cordova, California 95742
		Mailing Address:
		P.O. Box 537012
		Sacramento, California 95853-7012
Item 2
	(a)	Name of Person Filing:
		GenCorp Retirement Savings Plan (the “Plan”)
	(b)	Address or Principal Business Office or, if none, residence:
		P. O. Box 537012
		Sacramento, California 95853-7012
	(c)	Citizenship:
		Ohio
	(d)	Title of Class of Securities:
		Common Stock, $0.10 par value
	(e)	CUSIP Number:
		368682 10 0
Item 3.		If this statement is filed pursuant to §§240.13d-1(b) or 240.13d-2(b) or (c) check whether the person filing is a:
		(a)	¨	Broker or Dealer registered under Section 15 of the Act (15 U.S.C. 78o)
		(b)	¨	Bank as defined in Section 3(a)(6) of the Act (15 U.S.C. 78c)
		(c)	¨	Insurance Company as defined in Section 3(a)(19) of the Act
				(15 U.S.C. 78c)
		(d)	¨	Investment Company registered under Section 8 of the Investment
				Company Act of 1940 (15 U.S.C. 80a-8)
		(e)	¨	An investment adviser in accordance with §240.13d-1(b)(1)(ii)(E)
		(f)	x	An employee benefit plan or endowment fund in accordance with §240.13d-1(b)(1)(ii)(F)

	(g)	¨	A parent holding company or control person in accordance with §240.13d-1(b)(1)(ii)(G)
	(h)	¨	A savings association as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813)
	(i)	¨	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3)
	(j)	¨	A non-U.S. institution in accordance with §240.13d–1(b)(1)(ii)(J)
	(k)	¨	Group, in accordance with §240.13d–1(b)(1)(ii)(K). If filing as a non-U.S. institution in accordance with §240.13d–1(b)(1)(ii)(J), please specify the type of institution:
Item 4.	Ownership:
	(a)	Amount Beneficially Owned:
		3,204,262
	(b)	Percent of Class:
		5.3%
	(c)	Number of shares as to which such person has:
		(i)	Sole power to vote or to direct the vote: 0
		(ii)	Shared power to vote or to direct the vote: 3,204,262
		(iii)	Sole power to dispose or to direct the disposition of: 0
		(iv)	Shared power to dispose or to direct the disposition of: 3,204,262
Item 5.	Ownership of Five Percent or Less of a Class:
	Not applicable
Item 6.	Ownership of More Than Five Percent on Behalf of Another Person:
	The Plan is a voluntary savings plan for eligible employees of GenCorp Inc. and certain of its subsidiaries. Employees who elect to participate in the Plan may select one or more of twenty-three investment options for their contributions. Prior to April 15, 2009, an additional option was a fund (the “GenCorp Stock Fund”) investing solely in GenCorp common stock. Effective March 16, 2009, participant-directed exchanges into the GenCorp Stock Fund from other investment funds in the Plan were no longer permitted. Effective April 15, 2009, all future contribution investment elections directed into the GenCorp Stock Fund were redirected to other investment options. Prior to April 15, 2009, all matching company contributions were initially allocated to the GenCorp Stock Fund. Effective April 15, 2009, all matching contributions to a participant’s account, if any, are allocated in accordance with the participant’s investment elections for his own contributions. Under the terms of the Plan, Fidelity Management Trust Company (the “Trustee”) receives dividends on shares held in the GenCorp

	Stock Fund and is required to invest and reinvest the principal and income of the GenCorp Stock Fund in GenCorp shares. Participating employees ultimately receive such benefits as result from the performance of the GenCorp Stock Fund upon their election to take a distribution of their allocated shares from the GenCorp Stock Fund.
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person:
	Not applicable
Item 8.	Identification and Classification of Members of the Group:
	Not applicable
Item 9.	Notice of Dissolution of Group:
	Not applicable
Item 10.	Certifications:
	By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect.

Signature:

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.

Dated: February 5, 2013

By:	/s/ Christopher C. Cambria
Name:	Christopher C. Cambria
Title:	Vice President, General Counsel and Secretary of GenCorp Inc., on behalf of The GenCorp Retirement Savings Plan