I wasnt sure what section to put this in, but I figured this would be the place.

I have  a TASK converted M11/9, it uses an AR buffer tube and buffer to reduce the rate of fire. Its shooting pretty fast, and I'd like to slow it down by putting a heavier buffer in it. I have access to a lathe, and would like to make a solid tungsten buffer. My only question is, does a buffer need to have the reciprocating weights inside to function properly? Would a solid buffer work?

the spikes buffer is just a buffer packed with tungsten powder, so i'd say it should work.

..........only one way to find out

No idea how that would work in your application, but I don’t think it would be good for a regular AR.

The reciprocating weights cause a deadblow effect to combat bolt bounce especially in automatic weapons.
Spikes uses tungsten powder instead of slugs but it's not packed tightly.

9mmAR uses a solid buffer and the Slash (member) buffers are solid so they do work.

Why not try an H3 conventional ?

H3's still arent as heavy as what Im looking for. Id like it to be between 700-850 rpms. Right now with the H2 its still way too fast. Ive read that 8-8.5oz is what ill need to get it around my target speed. Since its an open bolt weapon, I would think the weights wouldnt really matter. Theres no bolt bounce to worry about, I just dont know for sure.

A solid buffer should be fine. What about the extended 9mm buffers? I think Spikes and Slash have some. Alternatively you might be able to use one of the VLTOR A5 kits. Or just make your own if you have a lathe.