ARH springs.

[tjk]

Chris, By negative with the tissue test, did you mean that you had air pushing the tissue off or did it stay I place? If so, you may need to replace he breech seal. From your chrony results, I would venture to say you have a broken or collapsed spring as the major culprit with your velocity variations. Allow me to offer a different view of what I might try in your case. When you take your gun apart, and if indeed the spring has been proven to be the reason for the drop in performance, carefully remove the piston and see if the seal has at all sustained any damaged. if it hasn't any signs of scratches or burn marks and blistering from dry firing, and it is still in a "used" pristine condition, I see no reason to replace it because it has already sized itself to the compression tube via  use. The simplest action would be to replace the Vortek spring kit and clean the tube, and carefully instal the original piston seal into the compression tube with the new innards and whatever lubrication techniques you so choose to administer. Another option,....if you still have the original OEM spring guide might be to try a Titan spring in you rifle. I have had very good results with the titan wire in all of my springers that Ive tried them in. Honestly, and Im not trying to dissuade you using any other brand spring,....except the OX springs ( that's a whole different story),...but I don't think I have ever had a spring fit exactly as another regardless of brand or duplicates of brands. If you install a spring on a guide and it is loose, flip it and see how the other side fits. You might be surprised how much differences can actually occur in the manufacturing process. Macarri makes excellent products as well as Vortek and Titan.  Just wanted to throw out a different perspective and something to consider. Hth's, tjk