Post tutorial RSS Aliens Colonial Marines: Editing game variables

This tutorial will teach you how to mod Aliens Colonial Marines (ACM) through editing Upk files via HEX editors. Sorri for bad english, I'm from russia. AND!! You cant add any thing, only change allreadi existing one.

Posted by on - Advanced Client Side Coding

First of. You cant use multiple mods created with this method if they edit came files. You must HEX merge theirs changes for that.

So, first you need a proper tools, they are:
1.Upk Decompressor (can get it here:

2.UE Explorer (can get it here: )

3.HxD Hex Editor (can get it here: )

Then you must go to Steam\steamapps\common\Aliens Colonial Marines\PecanGame\CookedPCConsole and BACKUP!! any *.upk and it's *.upk.decompressed_size files that you are going to mod, then put decompressor.exe to CookedPCConsole folder and create *.bat file like this one:

decompressor.exe -lzo [file to uncompress name without "[]" ].upk

and launch this bat file. folder named @uncompressed will be created and uncompressed upk will be inthere.

Next you delete BACKUPED TO SOME OTHER NOT SUB FOLDER original *.upk and it's *.upk.decompressed_size files and copy uncompressed to CookedPCConsole folder. There now must not be corresponding *.upk.uncompressed file or game will chash. you may delete @uncompressed folder now.

That was the easy part, now to hard one:


You open up your uncompressed upk with UE Explorer and looking there fore parameter you want to edit, fore example Mk2 PulsRifle RPM is listed in Objects->Content->DEFWPN_RPulseRifle->Weapon->Wep_RPulseRifle and there is variables FireInterval(pause betwin shots in part of second) and FireRate(rounds per minute)

But you cant edit it from here. The thing you can do here is find out how the variable parameter is looks in HEX and then fing it in *.upk using HEX Editor end modifie it. To find it you clik on "View" drop down button in upper right corner of UE Explorer ind CLICK ViewBuffer, not TableBuffer. This will bring you HEX representation of selected object (in out example Wep_RPulseRifle ). Now you must find position where name fieald on the left will represent variable name you are looking for (example FireRate). It is frustrating work, but there is no other way. After you found variable name you must check next positions one by one to find one that contains variable VALUE. It can be tricky. after you found that position - copy somewhere portion on positions with value for example "00 00 24 02 00 00 3D E4 00".


Open HEX Editor and open your uncompressed upk. Start loking for position portion that you copied vis Search tool, din't even try look with your eyes thought whole file. Whewn you found match - check with UE Explorers HEX view that tis is the right spot in file by matching other close positions. If you are shure that tis is rught spot - close UE Explorer (otherwhise you cant edit upk in HEX Editor), go a one ore two strings up and search for value with search tool, first one in your copied part must be the one you must edit.


Now you must somehow (use google) convert desiared value (900 for example) to hex representation like 83 04 and then REPLASE those positions with converted. If you add ore delese something from file and it's size changes - game will not start.

If you done all right then you save file and can start game.)

Hope this will help some one make other mods rater my Puls Rifle 900RPM and 95 Clip size mod.)

Wish you all good luck!!

Battou (Andrey Egorov, Russia)

agatsuma Author

Little eaddition. Float variables in UPK in HEX are REVERSED!! So 5.0 vill be not 40 A0 00 00 but 00 00 A0 40. Keep that in mind.

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Hi kann you bring a viedo tutorial for this?
I dont understand this.xD



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Is there a way to compress the file again after is edited? Because i want to edit the Aliens: Colonial Marines XBOX 360 version.

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Im not understanding the bat file you want me to make. Am I suppose to edit the bat file for every file I want to decompress?? Like

decompressor.exe -lzo [file to uncompress name without "[]" ].upk

Put the name of the file after the -Izo every time? It just keeps saying decompresser.exe is not a recognized internal or external command This is a needle in a haystack. Id have to decompress every upk file in this folder to find the gun values. Every time I look in UE at my decompressed file theres nothing there..

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