I run a server with RSM WW2 type rifles mod. I only have K98, Moisin and Enfield bolts enabled. For some reason gameplay is not smooth. Sometimes worse than others. As you move it sometimes stutters. Sometimes a few times a minute and sometimes not so much.
I also run Open-Warfare mod with custom maps. this mod runs fine.
Also runs fine un-modded.
This is a link showing mod: https://forum.i3d.net/threads/cod4-mod-rsm-snipermod-1-7.28263/
This is the server.cfg file:

//******************************************************************************
// Call of Duty 4 - RSM Modification
//********************************************************************************************************
// author : ZeRoY
// website : http://forums.raidersmerciless.com/index.php
// mod : RSM - Rifle Sniper Mod
// version : 1.5
// update : June 2008
//********************************************************************************************************

//******************************************************************************
// Color Codes
//******************************************************************************
// Colors for text. Do not clear the comment in front of the color codes.
// Useful for your server name, motd msg's - Information and ref use only
//
// ^1 = Red
// ^2 = Green
// ^3 = Yellow
// ^4 = Blue
// ^5 = Cyan
// ^6 = pink/Magenta
// ^7 = White
// ^0 = Black

//******************************************************************************
// Public Information
//******************************************************************************
sets sv_hostname "^2AMI-^2CLAN-^2BOLTS"
sets _Admin "[AMI]Amigaman"
sets _Email "xxxxxxxxxxxxxx"
sets _Website "ami-clan.com"
sets _Location "New York"
sets _Irc ""
sets _Mod "RSM"
sets _ModVer "v1.5"
sets _ModUpdate "06-07-08"
sets _Maps "CoD 4 stock"
sets scr_motd "Welcome"
set g_motd "Welcome"

//******************************************************************************
// Common Server Settings
//******************************************************************************
// Log Settings
set g_logsync "0" // 0=no log, 1=buffered, 2=continuous, 3=append
set logfile "1" // 0 = NO log, 1 = log file enabled
set g_log "rsm.log" // Name of log file, default is games_mp.log
set sv_log_damage "1"

// Network options
set net_ip "173.198.252.100" // Set your servers IP address
set net_port "28960" // Set your port number
set com_hunkMegs "512"
set net_noipx "1" // Allow ONLY tcp/ip protocol, player/server communications

// Server Network Mode
set dedicated "2" // 0 = Listen, 1 = LAN, 2 = Internet
set loc_warnings "0"

// Password Settings
set rcon_password "xxxxxxxx" // RCON must supply pw to use
set sv_privatePassword "" // Private slots, non-public slots

// The following can be used to lock out the server so that only those
// players that have been provide the password can connect. Good for
// matches, practices, etc.
set g_password ""

// Player slots setup
set sv_maxclients "12" // MAX server player slots, this is TOTAL player slots
//+set ui_maxclients "" In your commandline for slots over 32
set sv_privateclients "" // Number of private player slots, maxclients - privateclients = public slots

// Ping
set sv_minPing "0" // MIN player ping on CONNECT, any lower and player isnt allowed to connect
set sv_maxping "200" // MAX player ping on CONNECT, any higher and player isnt allowed to connect

// Client Download Settings. (0=off/1=on) Used for MODs and custom maps
// See included Quick Setup Guide for instructions.
set sv_allowdownload "1"
seta sv_wwwDownload "1"
seta sv_wwwBaseURL "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
seta sv_wwwDlDisconnected "0"

// Rate
set sv_maxRate "15000"

// FPS
//set sv_fps "20"

// Drop inactive players
set sv_timeout "900"
set sv_zombietime "1"
set g_inactivity "0"
set g_inactivityspectator "0"
set sv_reconnectlimit "3"

// Anti Cheat Settings
set sv_disableClientConsole "0"
set cl_autocmd "0"
set sv_cheats "0"
set sv_pure "1"
set g_banIPs ""
set g_no_script_spam "1"
set sv_punkbuster "0"

// Temporary Ban duration, in seconds
set sv_kickBanTime "180"

// Voting
set g_allowVote "0"
set g_voteAbstainWeight "0.5"
set g_oldVoting "1"

// Team balancing
set scr_teambalance "1"

// In-game voice communication system
set sv_voice "0"
set sv_voiceQuality "5"
set voice_deadChat "1"
set g_deadChat "1"
set voice_global "0"
set voice_localEcho "0"


//******************************************************************************
// Misc
//******************************************************************************
set sv_allowAnonymous "0"
set g_antilag "1"
set g_smoothClients "0"
set scr_drawfriend "1"
set scr_player_forcerespawn "1"
set scr_game_allowkillcam "0"


// HUD and Environmental Stuff
set scr_enable_music "0"
set scr_enable_scoretext "1"
set scr_fog_disable "1"


//******************************************************************************
// Init & Exec CFG Files
//******************************************************************************
wait
exec disableattach.cfg
wait
exec riflemod.cfg
wait
exec gametypes.cfg
wait
exec maprotation.cfg


Thank you for any help.