Great right up. I loved your TX 200 post and thanks for sharing. Hopefully, next time I hope you choose a break barrel. -Threaded tipped trigger pins. Was it difficult to thread the ends of the trigger pins? I assume that they are from hardened steel?-Do you prefer Moly or Krytox?-I thought it was "universally" accepted that 1:12 was the optimal twist rate to stabilize pellets? Could Diana's twist start further down the barrel? Maybe they borrowed an idea from FX? Thanks again for a great write up and your dedicated work!-Yogi+ you are a darn fine shot!
NitroC,Do you think that the size and shape of the Diana rifling is the reason that Diana's tend to shoot H & N pellets so well? I am assuming that the AA barrels shoot JSB and AA pellets better?-Y
Also less mass, less inertia, ability to generate pressure faster and to a higher level is always going to beat a big fat heavy piston with a shorter stroke, simple science.
Thanks Steve for your kind words.IF you ever have the time, I would like to see your rifle tested at altitude (3,000 FASL and up), as IMHE, it is the only shortcoming of the "skinny piston" idea. But with more data, we can elaborate on that.Also, please be aware that the shorter travel of action (and stock, when it is a solidly attached stock) upon firing is ALWAYS present in all shortstroked rifles.Mine run the normal diameter compression chamber but the action comes to rest at about 1/4" from the starting point.It is a function of the time it takes the gun to complete the shot cycle.Lastly, did you measure the cocking force? I would love to see some numbers at 30, 90, 120 and end of stroke (about 150) degrees of the cocking lever. Don't measure the LATCHING effort, as that is trigger tune dependent, not powerplant dependent. Just the powerplant "intake" of energy/work.Thanks!HM
Great write up as always. Good choice in optics also. I took a chance on that very scope and I have not been disappointed. Given some overtime hours I may contact Tony and have my 54 modified.
HectorAre you coming to the UK for the FT worlds in a few weeks? I bet if you are the first thing you do is adjust the rifle to suit the environment/altitude, you will no doubt set the gun down to around 8 to 10fpe for entry into the Uk then adjust the rifle up to 11 or so when at the competition? Steves rifle will do well over 12fpe is needed, in fact i can set 105mm stroke and push a .22 to 800fps with ease so adjusting for a little higher altitude is not an issue, plus he could always set 13fpe and not worry about a 30fps drop or so at FT ranges as you would never notice.This altitude argument you throw in is so predictable, i told Steve to wait for it coming and you did not disappoint Also less mass, less inertia, ability to generate pressure faster and to a higher level is always going to beat a big fat heavy piston with a shorter stroke, simple science.
Hi Hector, At some point I may try to set up some testing at elevation. I would run a series of tests at my current elevation with my 96mm x 22mm set-up vs the factory 105mm x 28mm set-up at my current elevation, and then repeat the same testing at greater elevation as you mentioned. I would suspect both 22mm and full size pistons would be affected. It would make for an interesting test. I will say this, with only 6mm total preload on this set-up, I can swap in a spacer in 5 minutes or less and be back on the bench ready to go for any changes I might see at elevation. The trigger block can be compressed back into place with only 2 fingers Regarding the long vs short stroke movement - Inertia due to piston weight also comes into play with the action movement. A while back I ran some testing between my 22mm TX200 .177 and my sub 12 fpe HW 98. My 22mm TX200 has a stroke of 90mm and the HW98 is shorter at only 85mm stroke with the 26mm factory piston. They were both tuned to near identical energy levels TX200 - 11.44 fpeHW98 - 11.53 fpeThe TX200 did not have a scope when I ran the recoil sled testing, and weighed in at 9.08 pounds. The HW98 had a scope and weighed in at 9.46 pounds. So, the HW98 was heavier. Despite being lighter, the longer stroked 22mm x 90mm TX200 had over 38% less total combined movement of the initial recoil and surge as compared to the shorter stroked 26mm x 85mm HW98. While stroke was shorter on the HW98, the piston was heavier and total movement was greater.I will try and get some measurements on the cocking effort. I have been wanting to do that on each of my 22mm builds, but never did. While I can feel the reduction, I would like to quantify with numbers the differences that I feel Intersting stuff, it's what keeps me going in this hobby Steve
Thanks, Steve!Hard Data is all I ask for.I find your recoil sled interesting, just to be sure that we are talking in the same terms (I will use the most common understanding in the shooting world to start):Recoil is the BACKWARDS movement of the gun (whether action alone, or stock and action), same definition as for ANY rifle or gun.Surge is the FORWARDS movement of the gun once the gun reaches its furthest rearmost position (due to recoil), and starts moving forwards.Am I correct?Since one direction of movement is back and the other fore, do you add the absolute numbers? Because otherwise TOTAL movement should always be LESS than the parts.Another doubt I have is how did you measure the stock recoil in a 56? With so many mods (less ball engagement, screw modifications, polished surfaces, Orings inserted) carried out between the Pre-kit and the Post-kit scenarios, how can we ascribe all changes to ONE item?And lastly, one consideration: Shouldn't you be measuring recoil/ft-lb? Otherwise the comparison is oranges to grapefruits.Last question: Have you ever put a powerful PCP in the sled?Sorry for the questions, but I really need to understand better your tests. It IS a fantastic write-up and a VERY worthwhile modification that suits your needs. Great job and congratulations again.Keep well and shoot straight!HM
Steve, Hector, and Tony-Thank all of you for this VERY interesting post. However, my simple mind begs the question, "If the major key to recoil/surge reduction is the weight of the piston, why don't manufacturers use lighter pistons?"Cost aside, would a piston made out of titanium be the perfect result?I realize that piston weight alone is not the only improvement that has resulted in the smoother shot cycle described by you and that a whole host of other factors are also at play.Thanks again for all the thoughtful insights! -Yogi