Only found one posting about this topic and it was from a few years ago. Just had a question about barrel lengths and suckback. I recently installed madbull tightbore barrels into my echo1 p90 and echo1 SCAR, both new barrels were 363mm in length. The original P90 barrel was 247mm and the SCAR was 300mm. Are these lengths gonna cause a problem if i don't upgrade my internals? I dont have enough room in my backyard to actually see if my distance has decreased due to suckback so I'm unsure if I'm experiencing it. They seem to shoot fine.