You can use this small guide to help you. I did not make it, and I found it somewhere on these forums, but I saved it in a word document format for future reference, but i'll just c/p the text:
Step1- You need to download a rez injector and Winrezlt.
Step2- When you are model swaping the ltb files need to be like this!
For example famas to L85a1
Example: Files needed to file swap Famas to L85A1,
Famas_Antibase****b>ANI_G_L85A1****B
PVMLA_AR_FAMAS****B>CM_HND_NM_DF_L85A1_SH****B
PVMLA_W_AR_FAMAS****B>CW_HND_NM_DF_L85A1_SH****B
CM_HND_SP_DF_FAMAS_CH****B>CM_HND_SP_DF_L85A1_CH** ** B
PV_AR_FAMAS.DTX>PV_AR_DF_L85A1_BC.DTX
Step3-Ok so what you do is take the Famas_Antibase****b and the ANI_G_L85A1****B and rename ANI_G_L85A1****B to Famas_Antibase****b.
And delete the original Famas_Antibase****b. So basiclly what you did was rename the l85a1 to the famas.
Step4- Take the PVMLA_AR_FAMAS****B and rename the CM_HND_NM_DF_L85A1_SH****B to PVMLA_AR_FAMAS****B. You can delete the original PVMLA_AR_FAMAS****B.
Step5- Take the PVMLA_W_AR_FAMAS****B and rename the CW_HND_NM_DF_L85A1_SH****B to PVMLA_W_AR_FAMAS****B. You can delete the original PVMLA_W_AR_FAMAS****B.
Step6- So take the CM_HND_SP_DF_FAMAS_CH****B and rename the CM_HND_SP_DF_L85A1_CH****B to CM_HND_SP_DF_FAMAS_CH****B. You can delete the original CM_HND_SP_DF_FAMAS_CH****B.
Step7- Take the CM_HND_SP_DF_FAMAS_CH****B and rename it to
CM_HND_SP_DF_L85A1_CH****B. YOu can delete the original CM_HND_SP_DF_FAMAS_CH****B.
Step8- So After this process you should have 4 ****B files.
Files you should have:
Famas_Antibase****b- this is acually the ANI_G_L85A1****B
PVMLA_AR_FAMAS****B this is acually the CW_HND_NM_DF_L85A1_SH****B
PVMLA_W_AR_FAMAS****B This is acually CW_HND_NM_DF_L85A1_SH****B
CM_HND_SP_DF_FAMAS_CH****B -This is acually CM_HND_SP_DF_L85A1_CH****B
Step9- Run rez injector and inject all 4 ****B files into Guns_M_PV_AR.REZ. Click inject and the rezinjector will make a .REZNEW all you do is take the Guns_M_PV_AR.REZ and replace it with GUNS_M_PV_AR.REZNEW.
Step10- Take the Famas DTX and the l86a1 DTX and rename the l85a1 dtx to the famas dtx.
Step 11- Inject the Famas dtx(AKA l85a1 dtx) and inject it into Guns_T_PV_AR.REZ. Rezinjector will have made a .reznew so what you do is rename the Guns_T_PV_AR.REZ and replace the Guns_T_PV_AR.REZNEW with Guns_T_PV_AR.REZ.
And you are done!!!
Keep these things in mind:
Antibase>Ant_G_
PVMLA>CM_HND_NM_DF_
Pvmla_W>CW_HND_NM_DF_
CM_HND_SP_DF_>CM_HND_SP_DF_
Anything that is blocked with *'s is .L TB (without the space between the L and the T)
The guide is kind of vague, so if you need a better explanation, I can provide a more detailed one.