Looking to cast in metal or resin some spare arms, legs, ammo pouches, water bottles. These are only for myself, UK caster preferred, tried the usual names in the casting game, but no luck so far, Any advice / Thank you in advance

If this is just for limited run you might also consider 3D printing. The price might be lower compared to resin casting which would also require a mold to be done.

Why not get a casting kit and give it a go yourself? Once you strip the mystery away,as with all things,it turns out it is not difficult at all!
This way you have the freedom to cast what you need and when you need it.
J

This is something I've only just started playing around at. I got a set from Amazon for about £30. It's a bit hit and miss to be honest but practice makes perfect.

Don't 3D printing companies, like Shapeways, require CAD files to produce the pieces? Plus, a few custom parts for a single customer is not cheap!

For those little parts it would be easier to learn it & do it yourself. Its not that hard. There are many DIY products on the market as well as DIY video's on youtube. Just duplicate existing pieces..as long as they are for your personal use.
Either that or sculpt your own out of clay then duplicate.

The ammo pouches are easy as long as they can have a flat, undetailed back. Just make an open top mold from RTV or silicon. You can even make temporary (single-use) molds for resin casting from plasticene. The mold will be distorted beyond use when removing the casting, but can be rolled up and used again. You just press your master into a blob of plasticene for the mold. Just don't expect commercial quality casting...expect air bubbles...batteries not included!

Dear all, I have tried to mould these myself but due to the shapes of the legs and pouches, they need to be pressure casted not gravity fed

I think you can still do this with an airtight box and a vacuum cleaner. I'm sure someone more knowledgeable can explain how it's done.

Have you tried a split mold? I have cast tens of thousands of parts over the space of almost two decades and have never used a pressure pot.
J