5.7x28 case + 80gr projectiles = ???

[amafrank]

You can contact sierra for info on what twist rate would be required or some of the barrel manufacturers can help with that too. There are ways to calculate stability and spin rate but I don't know them. You can find software to calculate the external ballistics. I think it ships with a number of chronographs like the ones from PACT. You should be able to find it online somewhere too. Check reloaders nest.

One reason for the lack of interest might be the low energy available from an 80gr bullet at 1K fps. More than a .22 LR but with a lot more expense. It seems the subsonic .223 interest has died too though there was a lot of work done some time back. I wonder if the 5.7 case has the powder capacity to spit out the 100gr sierra slugs at 1000 or so fps....that might be interesting but I think the bullets are special order only and expensive. I know they have 90gr available too. All in all its a pretty steep expense to get reamers, dies, brass and building the whole setup when for the same money you can do a 300. Thats my guess for the lack of interest.....neatness ratio is not high enough to offset the expense or useable alternatives.
Frank