I have been loading for a while but never necked down a case. Can somebody give me step by step instructions on necking a 284 down to a 6mm. I would also take brass that is already down appropriately, just can't find any 6mm-284.

What dies do you already have? If you already have FL standard 6mm-284 dies I would get 6.5-284 brass some Imerial sizing wax and just run it thru and that should be it.

Now if you have Bushing dies you should be able to take .284 brass down in two steps with appropriate bushings. I would measure the outside diameter after running thru a standard 284 die with the expander pulled out. Then buy bushing about halfway between that measurement and where you want to end up.

Your final bushing will depend on neck tension desired and by measuring brass neck thickness which can be explained easily enough but no sense until that point.

The only dies I have in the ballpark are 243 and 7mm-08

They wont work for sure.

Do you already have 284 brass? If not have you looked to find 6.5-284 brass instead of 284

Necking it down is as simple as running the 6.5x284 brass into a 6mm-284 die, and you're good.

If you have 284 brass, and neck it down to 6mm, the necks could become too thick. If you take 6.5x284 and neck it down (recommended), it will have it's own neck thickness different from the 284, and most likely a different brass I would select 1 brand of brass to work with when necking down, and stick with it. Otherwise you will have different internal case capacities and different neck thicknesses between different brands. If you size down 284(7mm) brass, you will want to do it in 2 steps- size to 6.5mm then to 6mm. Necking down 7mm to 6mm in one step is a .041", which is a lot in one sizing. The most I will go is .030" in one step. The easiest is to go 6.5x284 to 6mmx284.

In addition to what Chad said, I would recommend annealing right after necking it down. Otherwise, you may get split case necks after 2 or 3 firings.

Also, if the sizing process results in a case neck wall thickness .016 or greater, I would turn the necks.

Thanks guys

All the posts are correct and contain valuable info. If you don't have any Imperial sizing lube try some Hornady unique but make certain you are using a good lube and get a little dab inside the neck. Don't take a short cut and start loading without having a uniform neck wall thickness, but that is aanother subject in itself. JMO