6mmAI to 6-284 How much barrel set back would be required?

[AndyW]

I have an unfired but chambered 6mmAI barrel. Would a 6-284 reamer completely clean up the chamber, or would a set back be required?

Edit- I just measured the beginning of shoulder to end of neck on a 6mm AI case, .5" max set back should be all that is required, am I on the right track?

 

[Larryh128]

Compare a 6mmAI reamer print to a 6x284 print & check the distance to the start of the shoulder & also the end of the neck & see what the differences are. Looking solely at the cartridge drawings (not recommended) the shoulder should clean up but the neck is questionable. It appears that at worst, you could set it back 1 thread & be fine assuming that it's a 16 tpi thread. That would give you .0625 to play with.

 

[LCazador]

If you have to set it back an inch , 1/2 inch , one half dozen or the other . Make sure you also include a good clean on the throat too , so back it off a inch . Is 25fps velocity that important ?

 

[PALarson]

Give this a lot of thought, the 6-284 that I built was very fussy and about half wore out getting a pet load. The 6AI is a very good choice. easy to load for. much better barrel life and less expensive to shoot, my opinion is giving up much for very little.
Paul Larson Long range-Mid range HM