Trying to do three things this AM:
.177 AR2078 - 13 CI HPA @ 850 psi output - 3-12X scope
(old picture...but nothing external has changed)
click pix to enlarge
#1. Reset the power and air consumption. Used a lightened striker and a stronger hammer spring, looking at a fast, quick strike to the valve rather than a slow,heavy one.
#2. Shoot for groups as I wanted to test WC’s at it’s new speeds. Was hoping to find a cheaper WC that would shoot well enough for my short range use. Am mostly shooting at 20-30 yards, against small pest, and the “smack†of a WC works out just fine. Increasing the vel. of WC’s to 750-820 fps usually increases group size a bit. Don’t expect a 15 shot test to be definitive, but it should show the direction the rifle wants to go.
#3. Get velocity readings/variations along with shot count. To do #3 right, needed to shoot a complete fill (3,000 - 1000psi) with heavy pellets (10.6 gr. Kodiaks) and then refill it and shoot again with light pellets (7gr. RWS Basic). Was just keeping track of vel. readings.
Results:
#1. After some fiddling around, got it to shoot Kodiaks at 12 foot pounds (10.6gr. @ 714 fps average). Will shoot light weights faster, but to less energy (7gr. @ 822 fps). Hammer is now about 1/2 oz. lighter (started at 56 grams and is now 39 grams). Substituted an unknown spring from the parts box, right length and diameter but a bit heavier gauge, and ended up grinding the ends a little bit to get the rifle down to the 12 foot pound level.
Hard to judge by sound alone, but it sounds a bit quieter. Would guess that the light weight hammer shortens dwell time by letting the valve close faster.
#2. Couple of surprises. The cheap RWS basic pellets were expected to get a bit wild as I pushed them faster, but they shot nicely. The H&N’s seem to resent being shot faster. The Crosmans have never really shot worth a crap; weight is uniform but the diameter is too small for most of the barrels tried.
Considering cost and the max. distance I’ll be shooting, am going to use the RWS Basics in this rifle for backyard use (would not have bet on those little light weight pellets doing this
well).
Think the basic outcome is simple: Changing speed a little bit (about 100 fps from where it was set) does not seem to change over all accuracy, but it might change what pellets give that accuracy.
#3. 76 vs 71 shots. IF there was any real difference in air consumption between light and heavy pellets, it’s slight. MAY be a 5% increase in shot count with the heavy pellets. but to be truthful, to prove a 5% difference would need to run a lot more tests and i just don’t think that small amount of difference is worth testing for (because 5% could well be from some other cause...like the accuracy of the gauges).
Important part (at least to me) is that past tests using a heavy hammer to get to the same 12 foot pound level only gave 56-62 shots per fill. MAy be some overlooked causes, but it seems that the lighter hammer giving the same vel. is a useful decrease in air per shot.
The vel. DOES drop a bit as the tank pressure lowers. 10 shot string of Kodiak’s starting at 2900psi tank pressure showed 715 fps. 10 shot string starting at 1200psi showed 702 fps.. In both cases the high to low variation was 12fps (call it +/- 6 fps from average). Evidently at least some regulators don’t work as well at low pressures as they do at high.
RWS Basics ran from a high of 840 fps at high pressure to an average of 823 fps at low pressure. Vel variations were higher for those pellets in both tests ( +/- 11fps).
Thoughts:
HPA tanks are not all that efficient. Some energy has to go to working the regulator, and the only source of energy is the compressed air.
Still, getting 75 good consistent 12 foot pound(ish) shots (“consistent†using the less than +/- 20 fps yardstick) form a 13ci tank fill (3,000psi to 1,000psi) isn’t all that bad.
