pro sport .177 almost there!
Posted: Tue Dec 22, 2015 7:15 pm
after for what seems an ice age to get the pro sport to my liking, we believe we have got there. Now it's not quite nirvana due to of the limitations. my sport is FT but i want to keep the std stock, as in my opinion it is beautiful from every angle. another limitation is the way the cocking linkage attaches to the compression tube. i wanted to go further but aired on the side of caution.
i am not a fan of the mk3 long stroke, it in my opinion gives a lack of hold sensitivity, which also makes follow through difficult. so short stroke was going to play a part in my rifles make up. the simple things had to be done first though. Breach seals were changed, efficiency at keeping my compressed air transfering it's energy to the pellet is a must. stripping the trigger, and polishing the sears to a mirror finish to give a more precise and finer feel. i purchased an Air Arms mk2 spring from Julian Bond and sent it to Nick Stanning (tinbum) for some custom made delrin guides to suit the spring. i then bought a vortek O ring piston seal to fit on a piston fitted with a longer latchrod to achieve a stroke of 85mm. the piston complete weighed 233 grams. the transfer port was kept std. in this configuration it was a bit too effiecient. back to the drawing board. a lighter piston to reduce power and give a softer feel, as short stroking produces a harsher feel as everything happens faster was needed. the piston was fitted with a latchrod to give a stroke of 82mm and weighed 176 grams. once again no work was carried out on the transfer port. this piston was fitted with a Nick Gibney O ring conversion, he also did the work on the piston for me. in this format it gives a snappy feel, but the light piston gives a smoother softer feel. my compression tube seems efficient with the o ring seals giving very consistant FPS. stunning with JSB Express 7.9, shot five shot string out of tin, four came in at 805 fps, and one spoiled it at 802fps, Using JSB Exact 8.44, not quite as good consistancy but still giving 5 fps spread out of tin. average fps using these was 788 fps. happy days, just need to scope up and get some testing in.
at some time in future, i will get a TX 200, and try doing one full FT style, stock etc with a stroke circa 76-77mm, but we shall play with this PS first.
Gary.
i am not a fan of the mk3 long stroke, it in my opinion gives a lack of hold sensitivity, which also makes follow through difficult. so short stroke was going to play a part in my rifles make up. the simple things had to be done first though. Breach seals were changed, efficiency at keeping my compressed air transfering it's energy to the pellet is a must. stripping the trigger, and polishing the sears to a mirror finish to give a more precise and finer feel. i purchased an Air Arms mk2 spring from Julian Bond and sent it to Nick Stanning (tinbum) for some custom made delrin guides to suit the spring. i then bought a vortek O ring piston seal to fit on a piston fitted with a longer latchrod to achieve a stroke of 85mm. the piston complete weighed 233 grams. the transfer port was kept std. in this configuration it was a bit too effiecient. back to the drawing board. a lighter piston to reduce power and give a softer feel, as short stroking produces a harsher feel as everything happens faster was needed. the piston was fitted with a latchrod to give a stroke of 82mm and weighed 176 grams. once again no work was carried out on the transfer port. this piston was fitted with a Nick Gibney O ring conversion, he also did the work on the piston for me. in this format it gives a snappy feel, but the light piston gives a smoother softer feel. my compression tube seems efficient with the o ring seals giving very consistant FPS. stunning with JSB Express 7.9, shot five shot string out of tin, four came in at 805 fps, and one spoiled it at 802fps, Using JSB Exact 8.44, not quite as good consistancy but still giving 5 fps spread out of tin. average fps using these was 788 fps. happy days, just need to scope up and get some testing in.
at some time in future, i will get a TX 200, and try doing one full FT style, stock etc with a stroke circa 76-77mm, but we shall play with this PS first.
Gary.
