spyder MR4 chopping issue, need help
i have purchased a spyder mr4 a while back, and i have in the last few months upgraded it tremendously. upgrades include: spyder rocking trigger, bi pod, forgrip, collapsible stock, 22 inch barrel, red dot sight, and a pinokio hopper. all of which i love and though the gun is beefed out it has done me well. the most recent upgrade was switching from co2 to hpa. now originally i thought the velocity setting was no big change and of course i was very irritated when my gun acted more like a flame thrower then a sniper. now i have fixed the problem and i am shooting between 275 and 290 fps depending on the field i am at. the issue i am currently having and have had for a while, including on co2, is i am chopping still. maybe every 40th ball. not enough to effect my gun greatly, but enough to make me want to fix it. is there an acs bolt? is there something i am doing wrong? i take regular maintenance and the gun is in great condition. can someone help me with my issue or direct me to what i need done?