Echo 1 M28

Hello, I have the echo 1 M28 and its been giving me a lot of trouble. I was one of the first people to buy it so that was bad on my part. Here's my problem the piston broke (thats what you get when you use plastic) and my laylax one fits. Normally they dont fit but since mine was used a lot in my Jg Bar 10 it fits cause it's a little worn down. The reason Vsr 10 brand upgrades don't work is because the echo1's cylinder is too small. I've already upgraded the sears and I tried a better bucking but the bucking causes the bbs to misfeed. Back to my problem when I pull my bolt back it locks when I push it forword it goes but their is a slight resistance. Im afraid its gonna slam fire on the field. Should I keep it in?