5.7 x28mm Fn

[microgun]

Im having a barrel for my contender made in 5.7x28mm Fn with the exception of being necked down to 20 cal. Does anyone have any ideas about powders

[RareBear]

http://ammoguide.com/?catid=253

[microgun]

Thanks for the info. Im assuming(reluctantly) that all of this and any other data that i find is based on the FN pistol and its 5" barrel? I will be shooting the 20 cal version with 32 grn bullet out of an 18" barrel. Any guesses on max velocity?

[Rodgervich]

I have a .20x28, I call it the 5mm Shrike. I have only shot a few 32's in it and have not done additional load work with these bullets but the few I shot chronographed at 2500 ft/s in a 24" barrel.
QuickLoad shows you should be able to approach 2600 ft/s with the 32gr in an 18" barrel with 7.6gr Alliant 2400. This of course should be approached with EXTREME caution, this little case is very sensitive to load increments, work in .1gr at a time and I would recommend starting at 7.0gr. There is hardly any brass surrounding the primer so the pockets will loosen up quick if your chamber is sloppy, like my first couple attempts!
You need a really tight chamber to get the max performance from this case and it's variants but you can really get some juice behind small caliber pills in a bolt gun.