I haven't done a lot of tinkering with this at the high end of the power spectrum. I'd be tempted to increase (CW) spring tension and increase stroke (CCW) in small increments to flatten the string but maintain a high velocity.CCW on the stroke tends to lower the sweet spot pressure a bit too, so you can compensate by raising spring tension to compensate for the earlier engagement of the buffer. Not sure how much, if anything you'd gain, but it's worth a try.
I got the understanding that this was a set preload and vary travel to set velocity.
Quote from: PakProtector on October 22, 2012, 03:03:04 PMI got the understanding that this was a set preload and vary travel to set velocity.That's the KISS description for the average user who has little or no experience with tuning or the physics involved. It gets you to a good tune with minimal work and gives you good velocity control with a single adjustment. I didn't want to scare people off making the explanations sound too complex.If you understand what's really happening, there is always room for tweaking and fine tuning to optimize a specific tune you are looking for. Especially when working at the margins of the devices effectiveness as you are.
Glad to help.BTW What pellets were you shooting for that string and which o-rings did you decide to go with....hard or soft?
Res Shot vol closing Recorded developed EnergySHOT # PSI cubic in force lbs Stroke psi used velocity Friction fpe1 3200.00 0.2120 144.76 0.1143 52.185 883.40 6.948 43.9712 3147.82 0.2177 142.40 0.1162 52.714 885.50 6.835 44.1803 3095.10 0.2239 140.01 0.1182 53.295 887.50 6.721 44.3804 3041.81 0.2301 137.60 0.1203 53.840 890.60 6.605 44.6905 2987.97 0.2350 135.17 0.1225 54.013 889.40 6.488 44.5706 2933.95 0.2420 132.72 0.1247 54.617 891.00 6.371 44.7317 2879.34 0.2515 130.25 0.1271 55.704 897.40 6.252 45.3768 2823.63 0.2575 127.73 0.1296 55.930 896.10 6.131 45.2449 2767.70 0.2718 125.20 0.1322 57.866 908.00 6.010 46.45410 2709.84 0.2762 122.59 0.1350 57.574 902.00 5.884 45.84211 2652.26 0.2846 119.98 0.1380 58.064 901.90 5.759 45.83212 2594.20 0.2918 117.36 0.1410 58.230 899.10 5.633 45.54813 2535.97 0.3000 114.72 0.1443 58.522 897.20 5.507 45.35514 2477.45 0.3098 112.07 0.1477 59.039 896.30 5.380 45.26415 2418.41 0.3187 109.40 0.1513 59.039 895.00 5.251 45.13316 2359.37 0.3276 106.73 0.1551 59.456 890.00 5.123 44.63017 2299.91 This is a bit of data from my old tune before I enlarged the porting in my .25 madauder. Efficiency is only .89 as per Bobs method of calculating efficiency. I was using the B-staly method to achieve this string. I had also developed a tune using this method that produced 825-835-825fps over 10shots. It makes ballancing a tune very easy. In fact, even though I am able to achieve the same tune without the o-rings, I can do it much faster with the o-rings.( less pellets ) Here's the part that may interest you. If you observe shot 16, you will see the psi at that shot. It corrisponds with what is on the gauges. The volume for that shot is .328ci @2359psi. At this shot(16), the amount of air that could flow through this factory valve is .346ci @ 2359psi. If I shoot the next shot at the posted 2300psi, the velocity is 887.7fps using .337ci of a possible .343ci. Next shot would render 877fps using .342ci of .342ci. Here's the part that really tells the tale. The hammer stroke adjustment is 3 turns. with the adjusters screw pitch, that is .150" of stroke/ lift of the valve. The valve stem stands .250" proud and the o-ring stack-up is .312" high. when I account for the thickness of the sriker face that gives .250". In theory the valve shouldn't open, but it does. This is due to the compressability of the o-ring material, i'm sure. The amount of air that is released in this state is very small. In fact, I doubt that it would be enough to get the pellet to exit the bore. Why is this realivant? Look at the data above, Shot 16 stroke exactly. The subsiquent shots to #16 mentioned earlier, are calculated. My spread sheet generated that data (#17&18). So what do I do, increase the stroke by about 1/8 turn? Yep and the results were within 2% of the calculated outcome. The coincidence of the max possible flow at the given psi is equal to what did flow, indicates the end of the string. Also the coincidence of the adjusted stroke and the calculated stroke indicates no further gains in performance. These are by no means dump shots. At shot #18, the calculated valve duration is 1.5ms and the lock time of the pellet is a bit under twice that. The valve closes when the pellet is about 13" down the barrle. Any further shot get slower and efficiency gets lower. I have theory about the spike at shot #9. you'll notice that it used air at a gain not consistent to the trend. I think that is the point where the valve bounced dramaticly. I believe this is where the force closing the valve and the force opening were very close to equal and the consevation of momentum came into play as a fine example. (Newton's craddle). Once the ballance was upset, the apparent bounce subsided or atleast became deminished.Kick it aroundBill