<PAGE>   1


                                                                   EXHIBIT 10.15

                    STOCK SUBSCRIPTION AND PURCHASE AGREEMENT

                           DATED AS OF APRIL 23, 1998

                                     BETWEEN

                         FIREARMS TRAINING SYSTEMS, INC.

                                       AND

                       CENTRE CAPITAL INVESTORS II, L.P.,

                       CENTRE PARTNERS COINVESTMENT, L.P.,

                 CENTRE CAPITAL OFFSHORE INVESTORS II, L.P., AND

                  CENTRE CAPITAL TAX-EXEMPT INVESTORS II, L.P.


<PAGE>   2


                    STOCK SUBSCRIPTION AND PURCHASE AGREEMENT

                  STOCK SUBSCRIPTION AND PURCHASE AGREEMENT (the "Agreement"),
dated as of April 23, 1998, between Centre Capital Investors II, L.P., Centre
Partners Coinvestment, L.P., Centre Capital Offshore Investors II, L.P., and
Centre Capital Tax-exempt Investors II, L.P., as buyers (each a "Buyer" and,
collectively, "Buyers") and Firearms Training Systems, Inc., a Delaware
corporation, as seller ("Seller" or the "Company").

                             PRELIMINARY STATEMENTS

                  Buyers own beneficially and of record 10,594,060 shares of
Class A Common Stock, par value $.000006 per share ("Class A Common Stock"), of
the Company, with full voting rights. Centre Partners Management LLC and Centre
Partners II, L.P., which are affiliates of the Buyers (referred to herein
collectively with the Buyers as the "Centre Entities"), may be deemed to own
beneficially 571,181 shares of Class A Common Stock as a result of the terms and
provisions relating to voting rights contained in the Co-Investment Agreement.
Buyers desire to reduce the voting power in the Company maintained by the Centre
Entities such that the Centre Entities hold less than 50% of the total voting
power associated with the Class A Common Stock.

                  Buyers desire to purchase from the Company, and the Company is
willing to issue and sell to the Buyers, shares of the Class B Non-voting Common
Stock, par value $.000006 per share ("Class B Common Stock"), of the Company in
the amounts as set forth herein for consideration consisting of and in exchange
for an equal number of shares of Class A Common Stock and on the terms and
subject to the conditions set forth herein.

                  In connection with the issuance, sale and purchase of the
shares of Class B Common Stock, the Buyers are willing to waive irrevocably and
agree not to exercise any right to elect to convert the shares of Class B Common
Stock held by Buyers to shares of Class A Common Stock if, as a result of such
conversion, the Centre Entities would have the power to vote 50% or more of the
outstanding shares of Class A Common Stock, unless concurrently with such
conversion the shares of Class A Common Stock are transferred to an unaffiliated
Person; and the Buyers are willing to grant to the Company the right not to
recognize or carry out any such election to convert the shares of Class B Common
Stock. The Buyers will retain rights and obligations pursuant to the Buyer
Registration Rights Agreement in connection with the shares of Class B Common
Stock or shares of Class A Common Stock into which such shares of Class B Common
Stock can be converted.


<PAGE>   3

                  NOW, THEREFORE, in consideration of the mutual agreements
hereinafter set forth, Buyers and Seller agree as follows: 1. DEFINITIONS. In
this Agreement, the following terms have the meanings specified or referred to
in this Section 1 and shall be equally applicable to both the singular and
plural forms.

                  "AGREEMENT" has the meaning set forth on the first paragraph.

                  "BUYER" has the meaning specified in the first paragraph of
this Agreement.

                  "BUYER REGISTRATION RIGHTS AGREEMENT" means the Registration
Rights Agreement dated as of July 31, 1996 between the Company and the Buyers,
as amended, supplemented or otherwise modified from time to time.

                  "CENTRE ENTITIES" has the meaning specified in the Preliminary
Statements.

                  "CLASS A COMMON STOCK" has the meaning specified in the
Preliminary Statements.

                  "CLASS B COMMON STOCK" has the meaning specified in the
Preliminary Statements. "CLOSING" has the meaning specified in Section 4.

                  "CLOSING DATE" has the meaning specified in Section 4.

                  "CO-INVESTMENT AGREEMENT" means the Co-Investment Agreement
dated as of September 25, 1996 among the Buyers, Centre Partners II LLC, a
Delaware limited liability company, Centre Partners Management LLC, a Delaware
limited liability company, and certain other persons, related to the rights and
restrictions of the parties thereto with respect to the shares of Class A Common
Stock acquired from the Buyers by such persons, as amended, supplemented or
otherwise modified from time to time.

                  "COMPANY" has the meaning specified in the Preliminary
Statements.

                  "PERSON" means any individual, corporation, partnership, joint
venture, limited liability company, association, joint-stock company, trust,
unincorporated organization or Governmental Body.

                  "PURCHASE PRICE" has the meaning specified in Section 3.

                  "SECURITIES ACT" has the meaning specified in Section 7(f).
<PAGE>   4

                  "SELLER" has the meaning specified in the first paragraph of
this Agreement.

1.                INTERPRETATION. As used in this Agreement, the word
"including" means without limitation, the word "or" is not exclusive and the
words "herein", "hereof", "hereby", "hereto" and "hereunder" refer to this
Agreement as a whole. Unless the context otherwise requires, references herein:
(i) to Sections and Exhibits mean the Sections of and the Exhibits attached to
this Agreement; (ii) to an agreement, instrument or other document means such
agreement, instrument or other document as amended, supplemented and modified
from time to time to the extent permitted by the provisions thereof and by this
Agreement; and (iii) to a statute means such statute as amended from time to
time and includes any successor legislation thereto. Titles to Sections are
inserted for convenience of reference only and shall not be deemed a part of or
to affect the meaning or interpretation of this Agreement.

1.                AGREEMENTS TO PURCHASE AND SELL CLASS B COMMON STOCK IN
EXCHANGE FOR CLASS A COMMON STOCK. The Company hereby agrees to issue and sell
to each Buyer on the basis of the representations and warranties contained in
this Agreement, and each Buyer hereby severally subscribes for and agrees to
purchase from the Company the number of shares of Class B Common Stock set forth
next to its name on Schedule I hereto, with each Buyer acquiring such shares of
Class B Common Stock for consideration consisting of and in exchange for one
share of Class A Common Stock for each share of Class B Common Stock being
purchased by such Buyer (such aggregate consideration being the "Purchase Price"
with respect to such Buyer).

1.                CLOSING DATE. The sale and purchase provided in this Agreement
shall be consummated at a closing (the "Closing") to be held at 10:00 A.M.,
local time, on April 24, 1998, or such later date as may be agreed upon by
Buyers and the Company, at the offices of Sidley & Austin, 875 Third Avenue, New
York, New York 10022, or at such other place or at such other time as shall be
agreed upon by Buyers and the Company. The time and date on which the Closing is
actually held are sometimes referred to herein as the "Closing Date." The
failure of any Buyer to consummate the sale and purchase of such Buyer's shares
shall not relieve any other Buyer or the Company (except as to such failed
Buyer) of its or their obligations hereunder.

1.                PAYMENT OF PURCHASE PRICE; DELIVERIES AT CLOSING.

(a)               Subject to fulfillment or waiver of the conditions set forth
in Section 9, at or prior to the Closing, each Buyer shall deliver the shares of
Class A Common Stock representing the Purchase Price and appropriate stock
powers or a completed and executed Stock Assignment Separate from Certificate,
in the form of Exhibit A hereto, with respect to the number of shares of Class A
Common Stock
<PAGE>   5

constituting the Purchase Price, together with all documents required to be
delivered pursuant to Section 10 of this Agreement.

(a)               Subject to fulfillment or waiver of the conditions set forth
in Section 10, the Company shall deliver to such Buyer (i) one or more
certificates representing the shares of Class B Common Stock being purchased by
such Buyer, registered in such name and issued in such denominations as set
forth on Schedule I hereto or, if different, as the Buyer requests in writing
not later than two business days prior to the Closing, and (ii) the documents
required to be delivered pursuant to Section 9 of this Agreement.

1.                REPRESENTATIONS AND WARRANTIES OF BUYERS. As an inducement to
the Company to enter into this Agreement and to consummate the transactions
contemplated hereby, each Buyer individually represents and warrants as to
itself to the Company:

(a)               Each of Centre Capital Investors II, L.P., Centre Partners
Coinvestment, L.P., and Centre Capital Tax-exempt Investors II, L.P. is a
limited partnership duly organized, validly existing and in good standing under
the laws of the State of Delaware. Centre Capital Offshore Investors II, L.P. is
a limited partnership duly organized, validly existing and in good standing
under the laws of Bermuda.

(a)               Each Buyer has all requisite partnership power and authority
to execute, deliver and perform this Agreement and the Stock Assignment Separate
From Certificate. This Agreement and the Stock Assignment Separate From
Certificate have been duly authorized, executed and delivered by Buyer and are
the legal, valid and binding obligations of Buyer enforceable in accordance with
its terms.

(a)               The execution and delivery of this Agreement and the Stock
Assignment Separate From Certificate do not, and the consummation of the
transactions contemplated herein will not, conflict with, or result in any
violation of any material agreement or instrument, or any material term of any
judgment, decree, order, statute, rule or governmental regulation applicable to
Buyer, the violation of which would have any material adverse consequence on the
ability of Buyer to perform its obligations hereunder, or result in the creation
of any mortgage, lien, charge or encumbrance on the shares of Class A Common
Stock being paid in consideration to the Company.

(a)               Buyer is not required to obtain the consent, approval, or
authorization of, or to make any declaration or filing with, any governmental
authority as a condition precedent to the valid execution, delivery and
performance of this Agreement or the Stock Assignment Separate From Certificate.

(a)               Buyer is the owner of the shares of Class A Common Stock being
paid as consideration for the shares of Class B Common Stock being purchased by
such Buyer and will transfer such shares of Class A Common Stock to the Company
free and 
<PAGE>   6

clear of any liens, claims, charges, security interests or encumbrances, and has
full power and authority to possess and to transfer such shares of Class A
Common Stock in accordance with the terms and provisions of this Agreement.

(a)               Neither Buyer nor any Person acting on its behalf has paid or
become obligated to pay any fee or commission to any broker, finder or
intermediary for or on account of the transactions contemplated in this
Agreement.

(a)               The shares of Class B Common Stock are being acquired by Buyer
for its own account for investment purposes, and with no present intention of
selling or otherwise distributing the shares of Class B Common Stock within the
meaning of the Securities Act of 1933, as amended (the "Securities Act") except
pursuant to registration, or an applicable exemption from registration under the
Securities Act. Buyer is an "accredited investor," as such term is defined in
Regulation D promulgated under the Securities Act and/or Buyer has sufficient
knowledge and experience in financial and business matters to enable it to
evaluate the merits and risks of investment in the Class B Common Stock,
including the risks of owning non-voting shares. Buyer acknowledges that the
shares of Class B Common Stock being acquired have not been registered under the
Securities Act or any state securities laws, and are offered and sold pursuant
to exemptions therefrom; and will contain a prominent legend with respect to the
restrictions specified in this Section 6(g). Buyer acknowledges that in making
the investment decision to purchase the shares of Class B Common Stock it is not
relying on any representations, warranties or statements of the Company, other
than the representations, warranties and statements of the Company contained in
this Agreement. Buyer has been supplied with, or had access to, information to
which a reasonably prudent investor would attach significance in making
investment decisions sufficient to enable it to make its decision to purchase
the shares of Class B Common Stock.

1.                REPRESENTATIONS AND WARRANTIES OF THE COMPANY. As an
inducement to Buyers to enter into this Agreement and to consummate the
transactions contemplated herein, the Company hereby represents and warrants to
Buyers:

(a)               The Company is duly incorporated, is validly existing as a
corporation in good standing under the laws of its jurisdiction of
incorporation, and has full corporate power and authority to execute, deliver
and perform this Agreement. The execution, delivery and performance of this
Agreement by the Company have been duly authorized and approved by all necessary
corporate action, and do not require any further authorization or consent of any
other Person. This Agreement has been duly authorized, executed and delivered by
the Company and is the legal, valid and binding agreement of the Company
enforceable in accordance with its terms.

(a)               The execution and delivery of this Agreement does not, and the
consummation of the transactions contemplated herein will not, conflict with, or
result in any violation of or default (with or without notice or lapse of time,
or both) under, 
<PAGE>   7

or give rise to a right of termination, cancellation or acceleration of any
obligation or to loss of a material benefit under the certificate of
incorporation or bylaws of the Company, any material agreement or instrument, or
any material term of any judgment, decree, order, statute, rule or governmental
regulation applicable to the Company, the violation of which would have any
material adverse consequence on the ability of the Company to perform its
obligations hereunder or thereunder, or result in the creation of any mortgage,
lien, charge or encumbrance on the shares of Class B Common Stock being sold by
the Company.

(a)               The Company is not required to obtain the consent, approval,
or authorization of, or to make any declaration or filing with, any governmental
authorization as a condition precedent to the valid execution, delivery and
performance of this Agreement.

(a)               The certificates representing the Class B Common Stock to be
delivered under this Agreement are or will be in due and proper form under
Delaware law, and when duly countersigned by the Company's transfer agent and
registrar, and delivered to the Buyer against payment of the Purchase Price
therefor in accordance with the provisions of this Agreement, the Class B Common
Stock represented thereby will be duly authorized and validly issued, fully paid
and nonassessable, and will not have been issued in violation of any preemptive
rights or other rights to subscribe for or purchase securities.

(a)               The Company acknowledges that the shares of Class B Common
Stock acquired by the Buyers pursuant to this Agreement shall be subject to the
Buyer Registration Rights Agreement.

1.                EXPENSES; TRANSFER TAXES. The Company shall pay all costs and
expenses incident to the negotiation and preparation of this Agreement. Except
as set forth in the preceding sentence, each party hereto shall pay all costs
and expenses incident to its performance and compliance with all agreements and
conditions contained herein on its part to be performed or complied with,
including the fees, expenses and disbursements of its counsel and accountants.
The Company will pay all stock transfer or similar taxes, if any, in connection
with the initial issuance of the shares of Class B Common Stock pursuant to this
Agreement.

1.                CONDITIONS TO BUYER'S OBLIGATIONS. The obligations of each
Buyer to purchase the shares of Class B Common Stock pursuant to this Agreement
shall be subject to the satisfaction, on or prior to the Closing Date, of the
following condition, which may be waived, in whole or in part, at the sole
discretion of such Buyer:

         There shall have been no material breach by the Company in the
         performance of any of their covenants and agreements herein; each of
         the representations and warranties of the Company contained or referred
         to herein shall be true and 
<PAGE>   8

         correct on the Closing Date as though made on the Closing Date, except
         for changes resulting from any transaction expressly consented to in
         writing by Buyers.

1.                CONDITIONS TO THE COMPANY'S OBLIGATIONS. The obligations of
the Company to sell the shares of Class B Common Stock to each Buyer pursuant to
this Agreement shall be subject to the satisfaction, on or prior to the Closing
Date, of the following conditions, which may be waived, in whole or in part, at
the sole discretion of the Company:

(a)               There shall have been no material breach by such Buyer in the
performance of any of its covenants and agreements herein; each of the
representations and warranties of such Buyer contained or referred to in this
Agreement shall be true and correct on the Closing Date as though made on the
Closing Date, except for changes resulting from any transaction expressly
consented to in writing by the Company.

(a)               Buyer shall have executed and delivered or caused to be
delivered the following to the documents:

(i)               the Stock Assignment Separate from Certificate or stock powers
related to the shares of Class A Common Stock constituting the Purchase Price;

(i)               such additional supporting documents and certificates with
respect to the transactions contemplated herein as the Company may reasonably
request.

1.                IRREVOCABLE WAIVER OF CONVERSION RIGHTS.

(a)               Buyers acknowledge that the Class B Common Stock has no voting
rights, but in other respects is entitled to the same rights and powers as the
Class A Common Stock, and pursuant to the Fourth Article of the Certificate of
Incorporation of the Company, a holder of Class B Common Stock is entitled to
convert at the holder's election and at any time any or all of such holder's
Class B Common Stock into shares of Class A Common Stock at the rate of one
share of Class B Common Stock for one share of Class A Common Stock.

(a)               Notwithstanding the provisions of the Certificate of
Incorporation of the Company establishing conversion rights with respect to the
Class B Common Stock, the Company and the Buyers each severally agree as
follows:

(i)               the Buyers will not exercise, and hereby waive irrevocably,
any right to elect to convert shares of Class B Common Stock issued and sold
pursuant to this Agreement to shares of Class A Common Stock if, as a result of
such conversion, the Centre Entities would hold, of record or beneficially with
power to vote, more than 50% of the shares of Class A Common Stock outstanding
immediately following such 
<PAGE>   9

conversion, unless concurrently with such conversion the shares of Class A
Common Stock are transferred to an unaffiliated Person;

(i)               the Company shall be entitled to refuse to honor and carry out
an election to convert shares of Class B Common Stock in violation of clause (i)
above; and

(i)               the limitations on the conversion of the Class B Common Stock
issued and sold pursuant to this Agreement shall apply only so long as the
shares of Class B Common Stock are owned by any of the Centre Entities and do
not apply to a conversion exercised in connection with a sale or transfer of
shares of Class B Common Stock by the Buyers to a Person that is not an
affiliate of the Centre Entities.

1.                TERMINATION.

(a)               Anything contained in this Agreement to the contrary
notwithstanding, this Agreement may be terminated at any time prior to the
Closing Date:

(i)               by the mutual consent of any Buyer as to such Buyer and the
Company;

(i)               by any Buyer as to such Buyer or by the Company if the Closing
shall not have occurred as to such Buyer on or before April 30, 1998 (or such
later date as may be mutually agreed to by such Buyer and the Company);

(i)               by any Buyer as to such Buyer in the event of any material
breach by the Company of any of the Company's agreements, representations or
warranties contained herein; or

(i)               by the Company in the event of any material breach by any
Buyer as to such Buyer of any of such Buyer's agreements, representations or
warranties contained herein.

(a)               Any party desiring to terminate this Agreement pursuant to
this Section 12 shall give notice of such termination to the each other party to
this Agreement.

(a)               In the event that this Agreement shall be terminated pursuant
to this Section 12 all further obligations of the parties under this Agreement
shall be terminated without further liability of any party to the other,
provided that nothing herein shall relieve any party from liability for its
willful breach of this Agreement.
<PAGE>   10

1.                SURVIVAL OF OBLIGATIONS. All representations, warranties,
covenants, agreements and obligations contained in this Agreement shall survive
the consummation of the transactions contemplated by this Agreement.

1.                NOTICES. All notices or other communications required or
permitted hereunder shall be in writing and shall be deemed given or delivered
(i) when delivered personally, (ii) if transmitted by Fax when confirmation of
transmission is received, or (iii) if sent by registered or certified mail,
return receipt requested, or by private courier when received; and shall be
addressed as follows:

                  If to a Buyer, to:

                  Centre Partners Management LLC
                  30 Rockefeller Plaza
                  New York, New York 10020
                  Attention:  Scott Perekslis
                  Facsimile No: 212-332-5801

                  If to the Company, to:

                  Firearms Training Systems, Inc.
                  7340 McGinnis Ferry Road
                  Suwanee, Georgia  30174
                  Attention:  President
                  Facsimile No:  770-813-0741

or to such other address as such party may indicate by a notice delivered to the
other party hereto.

1.                SUCCESSORS AND ASSIGNS. The rights of the Buyers under this
Agreement shall not be assignable by such party hereto prior to the Closing
without the written consent of the Company. This Agreement shall be binding upon
and inure to the benefit of the parties hereto and their successors and
permitted assigns. Nothing in this Agreement, expressed or implied, is intended
or shall be construed to confer upon any Person other than the parties and
successors and permitted assigns any right, remedy or claim under or by reason
of this Agreement.

1.                ENTIRE AGREEMENT; AMENDMENTS. This Agreement and the Exhibits
referred to herein and the documents delivered pursuant hereto contain the
entire understanding of the parties hereto with regard to the subject matter
contained herein or therein, and supersede all prior agreements, understandings
or letters of intent between or among any of the parties hereto. This Agreement
shall not be amended, modified or supplemented except by a written instrument
signed by an authorized representative of each of the parties hereto.
<PAGE>   11

1.                WAIVERS. Any term or provision of this Agreement may be
waived, or the time for its performance may be extended, by the party or parties
entitled to the benefit thereof. Any such waiver shall be validly and
sufficiently given for the purposes of this Agreement if, as to any party, it is
in writing signed by an authorized representative of such party. The failure of
any party hereto to enforce at any time any provision of this Agreement shall
not be construed to be a waiver of such provision, nor in any way to affect the
validity of this Agreement or any part hereof or the right of any party
thereafter to enforce each and every such provision. No waiver of any breach of
this Agreement shall be held to constitute a waiver of any other or subsequent
breach. 

2.                PARTIAL INVALIDITY. Wherever possible, each provision hereof
shall be interpreted in such manner as to be effective and valid under
applicable law, but in case any one or more of the provisions contained herein
shall, for any reason, be held to be invalid, illegal or unenforceable in any
respect, such provision shall be ineffective to the extent, but only to the
extent, of such invalidity, illegality or unenforceability without invalidating
the remainder of such provision or provisions or any other provisions hereof,
unless such a construction would be unreasonable.

1.                EXECUTION IN COUNTERPARTS. This Agreement may be executed in
two or more counterparts, each of which shall be considered an original
instrument, but all of which shall be considered one and the same agreement, and
shall become binding when one or more counterparts have been signed by each of
the parties hereto and delivered to the Company and each of the Buyers.

1.                GOVERNING LAW. This Agreement shall be governed by and
construed in accordance with the internal laws (as opposed to the conflicts of
law provisions) of the State of New York.

1.                SUBMISSION TO JURISDICTION. The Company and Buyers hereby
irrevocably submit in any suit, action or proceeding arising out of or related
to this Agreement or any of the transactions contemplated hereby or thereby to
the non-exclusive jurisdiction of the United States District Court for the
Southern District of New York and the jurisdiction of any court of the State of
New York located in the city and county of New York and waive any and all
objections to jurisdiction that they may have under the laws of the State of New
York or the United States and any claim or objection that any such court is an
inconvenient forum.


<PAGE>   12


                  IN WITNESS WHEREOF, the parties hereto have caused this
Agreement to be executed the day and year first above written.

                                     BUYERS

                                        CENTRE CAPITAL INVESTORS 
                                     II L.P.,

                                        CENTRE CAPITAL OFFSHORE INVESTORS 
                                     II, L.P.

                                        CENTRE CAPITAL TAX-EXEMPT 
                                     INVESTORS II, L.P.

           by: Centre Partners II, L.P. as general partner of such partnerships

                        by: Centre Partners Management LLC, attorney-in-fact

                                     by: /s/ Jonathan H. Kagan
                                         --------------------------------
                                             Jonathan H. Kagan
                                             Managing Director

                                        CENTRE PARTNERS
                                     COINVESTMENT,  L.P.

                         by: Centre Partners II LLC, as general partner

                                     by: /s/ Jonathan H. Kagan
                                         --------------------------------
                                             Jonathan H. Kagan
                                             Managing Director

                                     SELLER

                         FIREARMS TRAINING SYSTEMS, INC.

                           by:  /s/ Peter A. Marino
                                --------------------------------
                                Name:  Peter A. Marino
                                Title: President and CEO
  
<PAGE>   13


                                   SCHEDULE I
<TABLE>
<CAPTION>

Buyer                                                         Number of Shares
-----                                                         ----------------
<S>                                                           <C>
CENTRE CAPITAL INVESTORS II, L.P.,                                1,162,360

CENTRE CAPITAL OFFSHORE INVESTORS II, L.P.                          230,322

CENTRE CAPITAL TAX-EXEMPT INVESTORS II, L.P.                        129,942

CENTRE PARTNERS COINVESTMENT, L.P.                                  171,945
</TABLE>