When I got my 1st AR (a Diamondback DB15), I eventually put a Fostech Echo 2 Trigger in it, and at first, I had trouble with the trigger & bolt getting out of sync when I used Echo mode. Putting an H3 buffer in the rifle with the factory buffer spring solved that for the DB15, & the Echo runs great in it.

Since then, I put together an AeroPrecision EPC pistol build chambered in 9mm, and heard that it would be good for felt recoil to use a heavy buffer (7 or 8 ounces) and a .308 spring, which I did. The EPC pistol runs just fine with a Timney Impact trigger or with the Echo trigger in regular semi-auto mode, but I can’t get Echo mode to work with it without the bolt & trigger going out of sync. What weight of buffer & what buffer spring should I put in the EPC-9 to get Echo mode to work reliably with it?

AR-9's can be finicky about triggers os you may never get a binary to run in it.  Regardless, dump the 308 spring.  It is a solution in search of a problem.

Gotcha…What issues could a .308 spring cause? And what kind of spring would you recommend instead?

Yours is not the 1st thread about fostech triggers in 9mm builds.....


  Click here for google results about previous threads from the AR15com forum

The stiffer spring can force cases into the chamber that may contact the edge of the feed cone causing bullet setback.  Some manf's, like F/M suggest one because their feed cone is tight and it does just that.  Guys that have moved to a standard 5.56 carbine spring have not had any issues with feeding and if there are issues they should be corrected by Macon reprofiline the feed cone rather than forcing the issue.

Get a Sprinco red buffer spring and a deadblow buffer. The combined weight of the buffer and BCG should be between 22 and 24oz.

Understood…Thanks!

Thanks for the recommendation!