GTA
All Springer/NP/PCP Air Gun Discussion General => American/U.S. Air Gun Gates => Daisy Gate => Topic started by: pblawler on November 10, 2022, 03:17:36 PM
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So I just swapped in a 1977 valve seal in a new 800 to see how it would affect the power. It reacted as expected. The 1977 abutment is steel and smaller in diameter than the 880 so it provides more volume in the compression chamber. This provides more pressurized air to push the pellet but at the expense of having to pump more to get the same pressure as the stock valve. For the first test I used the stock piston head. The next test I will swap the factory valve seal back in and put the 1977 piston rod in and see what we get (probably more FPS per pump). Lastly I'll put both the 1977 piston and valve in and see what we get, (I'm betting a significant power increase at higher pump numbers i.e. 15 to 20 pumps). At 30 pumps (lol yes 30) the 1977 valve made 12 FPE. All testing is done with H&N Baracuda pellets (10.65 grn). I'm hoping for 14 FPE (770 fps @ 10.65grn) at 15 to 20 pumps with the piston and seal from the 1977.
(https://i.postimg.cc/pdjYDkqs/20221110-121313.jpg)
(https://i.postimg.cc/J0MfwssW/20221110-121428.jpg)
The interesting thing is the 1977 valve is significantly slower at lower pump counts but doesn't fall off like the stock valve at high pump counts. Getting the higher compression piston in there should be a big gain while lowering the pump count. The 1977 valve is $3 from Daisy so its a low cost upgrade but probably only worth it if 1977 piston can get the pump count down to something reasonable. The pump head assembly is $10 from Daisy so if the two together make a significant power increase that's a good upgrade for $13.
Stock Piston
Average FPS
Stock valve 1977 valve
10 Pumps
610 575
12 Pumps
641 602
15 Pumps
663 632
20 Pumps
682 664
25 Pumps
688 684
30 Pumps
690 710
To be continued.....
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So yes the 1977 piston in the 880 is crazy! Very nice for $10. This test was with the factory 880 seal.
H&N Baracuda 10.65 grn
10 Pumps Avg FPS 654 FPE 10.11 44 FPS increase over stock
12 Pumps Avg FPS 687 FPE 11.16 46 FPS increase over stock
15 Pumps Avg FPS 721 FPE 12.29 58 FPS increase over stock
20 Pumps Avg FPS 750 FPE 13.30 60 FPS increase over stock
This upgrade makes the same energy with 20 pumps at 20 yards that it did stock at the muzzle with 20 pumps. Another way to look at it is it makes the same energy with 20 pumps at 40 yards that it does factory at the muzzle at 10 pumps.
OK to get the 1977 piston in the 880 is pretty straight forward. So in the first test with the 1977 valve seal the pressure bent the abutment pin slightly. I highly recommend upgrading this pin to 1/8" oil hardened drill rod. Drill rod is cheap. Just cut it the same length as the factory pin and it will slide right in. The image below is the bent factory pin next to the drill rod.
(https://i.postimg.cc/SQHcgvxL/20221110-135547.jpg)
The 1977 piston rod and 880 seen below. Notice the piston face to end of the rod is the same. The main difference is the pivot pin location. So I just removed the pistons and put the 1977 piston on the 880 rod.
(https://i.postimg.cc/HxXTdnbk/20221110-133809.jpg)
Just clamp the piston assembly and tighten to release pressure from the retaining pin. Then tap out the pin with a punch. To reassemble, clamp the assembly again to raise the pin hole in the piston so the retaining pin can be tapped back in place. Center the pin so it does not touch the cylinder when installed.
(https://i.postimg.cc/h4sHxV4q/20221002-004210-1.jpg)
The 1977 piston on a 880 piston rod. Notice the pivot location is the same from the piston face to the pivot location.
(https://i.postimg.cc/28q26WVG/20221110-135325.jpg)
After I assembled the piston into the gun I discovered the piston was barely pulling air. Turns out the second o-ring barely makes it to the cutout in the cylinder. That caused the gun to barely build pressure. I ended up filing the slot in the cylinder lower 1/8". Be sure to clean the inside of the cylinder good after filing and reoil. Also be careful not to scratch the inside of the cylinder when filing the slot.
(https://i.postimg.cc/26hLMz64/20221110-143817.jpg)
The piston was a great improvement. I think the 1977 valve seal with the 1977 piston in the 880 may bring the FPS back down without pumping more than 20 times but I'll test it just to be thorough. In anycase a $10 piston upgrade to get this improvement is awesome. I'm gonna try it in my older 880 also.
If anyone is interested in ordering these parts see the thread below.
https://www.gatewaytoairguns.org/GTA/index.php?topic=203427.0 (https://www.gatewaytoairguns.org/GTA/index.php?topic=203427.0)
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I chrono'ed the 880 with both the 1977 Piston and valve. The valve brought the velocity down as expected but it was significantly higher with the 1977 piston vs the factory piston. I assume like the factory piston and 1977 valve that at pump counts over 25 or so the combination would out preform the other combinations but I'm not interested in pumping that much and I doubt many other people are either.
1977 Piston and valve H&N Barracuda 10.65 grn
10 Pumps Avg FPS 631
15 Pumps Avg FPS 702
20 Pumps Avg FPS 738
The last thing I will test is drilling the transfer port to 0.125" and retesting with the factory valve and 1977 piston. After that I will put a 1977 piston in the "old style 880" and see what gains can be made.
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I think I have found the optimum setup to get the most power from an 880. I drilled the transfer port to 0.125" and my findings were not impressive. It actually lost velocity below 15 pumps (5 fps down at 10 pumps) but was 5 fps faster at 20 pumps. So I don't think it is worth the risk to drill out the transfer port. In short just swapping the pump head for a 1977 pump head results in maximum power. So for a $10 upgrade you can make a monster 880. I went back and chrono'ed two other pellets to see how they would perform.
JSB Exact 8.4 grn
20 pumps Avg FPS 809 FPE 12.26
H&N Barracuda 10.6 grn
20 pumps Avg FPS 758 FPE 13.39
JSB Beast 16.2 grn
20 pumps Avg FPS 644 FPE 14.92
So with JSB Beast pellets the 880 made 14.92 FPE!
A 15 FPE 880 is serious! I'm done power moding the 880 I don't think it can be pushed any further. Now lets see what that piston does in the older models.
This is a new 880 with a 1977 butt stock, bb door block off, handguard foregrip, and LDC. The other mods are removed flat spring, oil hardened drill rod abutment pin, and 1977 piston head. This gun makes 15 FPE with JSB 16.2 grn pellets at 644 fps, and 12 FPE with JSB Exact 8.4 grn at 809 FPS, at 20 pumps.
(https://i.postimg.cc/C5yKjGFq/20221117-140948.jpg)
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I installed the 1977 piston in a 87 model 880 and can hear it hiss around the valve seal when the pump head is bottomed out. As soon as I pull the pump lever up it stops. So there must be some interference with the abutment and piston head. I think it would take a lot of trial and error cutting piston rod pivot holes to get it just right. Given my schedule and lack of piston rods I'm willing to ruin, I think the 1977 piston in the older style guns is a no go. To get it to work the cylinder must be notched further like the newer guns. I used a spare piston rod and cylinder for this test but I am going to put the originals back in and enjoy the ole girl just the way she is. So 1977 upgrades are a definite improvement for the newer style 880s (non-brass non-ringed cylinder) but won't work for the older style guns without a custom piston rod. I have two 1977 piston rods I have no use for so one day I may revisit this for the old style guns.
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Patrick!!!! You are the man!!! The 1977 piston head is bananas in my 880 .22 conversion. I don't have a Chrono but these crosman hp 14.3 grains get to 20 yards really fast now. I used to be able to see them travel. Not the case now. I'm going to upgrade the head on my .177 Daisy 901. Happy Thanksgiving airgunners!
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I installed the 1977 piston in a 87 model 880 and can hear it hiss around the valve seal when the pump head is bottomed out. As soon as I pull the pump lever up it stops. So there must be some interference with the abutment and piston head. I think it would take a lot of trial and error cutting piston rod pivot holes to get it just right. Given my schedule and lack of piston rods I'm willing to ruin, I think the 1977 piston in the older style guns is a no go. To get it to work the cylinder must be notched further like the newer guns. I used a spare piston rod and cylinder for this test but I am going to put the originals back in and enjoy the ole girl just the way she is. So 1977 upgrades are a definite improvement for the newer style 880s (non-brass non-ringed cylinder) but won't work for the older style guns without a custom piston rod. I have two 1977 piston rods I have no use for so one day I may revisit this for the old style guns.
Mr. Trey,
I believe the 1977 piston is longer to accommodate the coil spring and 2 O-rings.
If you installed it on a standard 880 pump link, the resulting assembly would indeed be longer.....
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I installed the 1977 piston in a 87 model 880 and can hear it hiss around the valve seal when the pump head is bottomed out. As soon as I pull the pump lever up it stops. So there must be some interference with the abutment and piston head. I think it would take a lot of trial and error cutting piston rod pivot holes to get it just right. Given my schedule and lack of piston rods I'm willing to ruin, I think the 1977 piston in the older style guns is a no go. To get it to work the cylinder must be notched further like the newer guns. I used a spare piston rod and cylinder for this test but I am going to put the originals back in and enjoy the ole girl just the way she is. So 1977 upgrades are a definite improvement for the newer style 880s (non-brass non-ringed cylinder) but won't work for the older style guns without a custom piston rod. I have two 1977 piston rods I have no use for so one day I may revisit this for the old style guns.
Mr. Trey,
I believe the 1977 piston is longer to accommodate the coil spring and 2 O-rings.
If you installed it on a standard 880 pump link, the resulting assembly would indeed be longer.....
The pivot location to piston face must be longer but the completed assembly length is the same. It works for the new style seals but not the older design. Its a huge drop-in increase in the newer guns (pinned abutment). The pin hole location is higher in the 1977 piston to compensate for the longer dual oring piston. I think the difference
is very slight in the final assembly on an 880 rod, but just enough to be a problem for the older guns. I'm gonna try and replace the elastomer on the older guns with the 1977 spring. I should be able to shim it with washers to make it work. Still not a bad deal for the spring at $10. When I get the 822 in I'll try to swap a 1977 piston in and see what she does.
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Patrick!!!! You are the man!!! The 1977 piston head is bananas in my 880 .22 conversion. I don't have a Chrono but these crosman hp 14.3 grains get to 20 yards really fast now. I used to be able to see them travel. Not the case now. I'm going to upgrade the head on my .177 Daisy 901. Happy Thanksgiving airgunners!
It's a game changer for the 880! Happy shooting and happy Thanksgiving.
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Made a video of the PBL power mod process for making the parts.
https://youtu.be/MFofkAAqYlE (https://youtu.be/MFofkAAqYlE)
https://www.gatewaytoairguns.org/GTA/index.php?topic=205177.0 (https://www.gatewaytoairguns.org/GTA/index.php?topic=205177.0)
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Great video instructions!
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Something I forgot to mention in the video. When you reassemble the gun, if you hear a sucking or hissing sound at the top of the pump stroke then there are two causes. The most likely is that the notch in the cylinder is not deep enough and it is struggling to get air into the cylinder. The second cause is one or both of the piston o-rings are cut. Either and both will cause a loss of performance. The fix is to remove the cylinder and cut the notch deeper, I suggest no more than 1/16" at a time. More than likely if will not require very much, unless you stopped well before the bottom of the notch in the fixture. Cut o-rings will also make a sucking sound so check those first.
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If anyone wants one of these mods and does not have the means to make it please send me a PM. I made up a few kits.
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Just bought an 880 to do the 1977 piston mod.
Nice to know a little extra power is there if needed.