Quote from: HYspd on July 29, 2014, 10:22:26 PMyeah what he said! (points at Bob's post)...in my world, .25 pellets are easier to load and are much easier to drive to higher energy levels... 50+fpe packs a heck of a wallop...I shot a ream of paper standing on it's side with the writing side facing to gun at 15 yards with a BT-65 in .25 and it jumped off the table screaming in agony....And what would it have done with 28 grain soft hollow point in .177 cal at 900FPS (50FPE)? As long as the pellet expanded on impact well enough it would likely have jumped just as much.To get a 28 grain .177 cal pellet just use a slightly longer mini-ball mold than you do for a 21 grain .177 cal pellet. And hollow point Mini-ball are easy to cast . I admit that I rarely cast my own pellets as it is so convenient to buy them pre-made.Yes it does take a smaller volume of much higher pressure to get that kind of energy out of a .177 cal pellet as compared to a .22 or .25, though it can still be done.
yeah what he said! (points at Bob's post)...in my world, .25 pellets are easier to load and are much easier to drive to higher energy levels... 50+fpe packs a heck of a wallop...I shot a ream of paper standing on it's side with the writing side facing to gun at 15 yards with a BT-65 in .25 and it jumped off the table screaming in agony....
Quote from: Bullit on July 30, 2014, 07:42:52 PMYouch! Do you wanna hold it? Or rely in it? Didn't Lloyd block&bolt down a PCP supply and barrel, and try something like this, in his lab? If it wasn't him...I don't blame him, he's a sharp cookie, so I could be wrong.yep I think I saw the video but it was a .25ah found it
Youch! Do you wanna hold it? Or rely in it? Didn't Lloyd block&bolt down a PCP supply and barrel, and try something like this, in his lab? If it wasn't him...I don't blame him, he's a sharp cookie, so I could be wrong.
for a full dump it will likely require a valve volume of approximately 0.0124 cubic inches and a valve pressure of approximately 3200PSI for a 21 inch barrel for around 850FPS with a 21 grain .177 pellet.
Any chance you have this data for a .25 cal JSB King 25.4gr out of an Gen1 Mrod w factory Green Mountain barrel??
Quote for a full dump it will likely require a valve volume of approximately 0.0124 cubic inches and a valve pressure of approximately 3200PSI for a 21 inch barrel for around 850FPS with a 21 grain .177 pellet.Good luck with that.... 0.0124 CI = 0.203 cc, you will need at least 50 times that valve volume, even at 3200 psi.... That will have a significant effect on your number of pumps to reach 3200 psi.... 3200 psi with a 0.80" diam. piston requires a pumping force of 1607 lbs.... My Millenium Pumper peaked at less than half that load (773 lbs.) and it was a bear to pump.... It required 80 pumps to fill the 28 cc valve to 1800.... and 3200 would have been impossible.... The lever was an extended Mac1 Billet linkage for a 392.... 3" longer than stock.... Even if the billet linkage didn't bend or break, you wouldn't have been able to close the pump at that pressure.... Your statement that for a given weight and velocity a .177 will have a better BC and penetration is correct.... GETTING there is the problem, compared to the relative ease with a quarterbore.... I know you've got your heart set on proving it can be done and that everyone is wrong.... so I suggest you just hop to it and show us the results.... Bob
One fifth of the (21") barrel volume (8.5 cc) would be 1.7 cc = 0.104 CI, not 0.0124 as you stated.... Using that 1.7 cc and 3200 psi, with a dump shot, Lloyd's spreadsheet predicts from 623-688 fps depending on the efficiency you achieve (it could be less, of course, if you don't get the porting right).... If you increase the valve to 100% of barrel volume (8.5cc = 0.52 CI) valve, I get 818-899 fps.... With a 50% valve (and you will remember that is the point above which efficiency goes into the dumper), I get 752-827 fps....However, you have your own ideas and calculations, and I wish you the best in proving them out....BTW, I notice you are dropping your velocity targets, and you made the statement that I recommend staying below 850 fps, which is NOT correct, I recommend staying below about 960 fps (Mach 0.85) to avoid transonic effects.... With a good bullet shape you can probably push to Mach 0.9 (1017 fps)....Bob