I am building an AR with a 16" LMT M4 upper receiver. It will also have a collapsible stock.  Which buffer should I use?

not to hijack here.....but can someone please explain why one buffer over the other when they answer this?  just wanting to learn something here

I have used CAR, H, and 9mm buffers with my LMT M4 and they all work fine.

Many want to reduce recoil where others want to alter the firing cycle. Like the above poster posted the Standard LM&T Carbine buffer works fine with almost all .223/5.56 Ammos.

I have tried the Endine Carbine Hydraulic buffer It works well with NATO type 5.56 but has problems with less powerful .223 Ammos. This was the fact in both my LM&T and S&W 16" ARs.

I bought and H buffer at last firearm show and plan on giving it a test.