New Parts for my 2260 & 2560 HPAs

[rsterne]

I'm in the process of tweaking my 2560 HPA.... nothing major, just seeing if I can get a squeek more power (like 46 FPE isn't enough!), and more shots by changing to an 18 CI tank instead of the 13 CI, still regulated to 1600 psi.... The smaller tank is moving over to my 2260 HPA which is getting a reversed tank block like the .25 cal has now.... I'm hoping that the much larger plenum (the entire 2260 tube) will give me the same power (36 FPE for the .22 cal) on 1600 psi as I was getting on 1800 with the small volume between the regulator and valve it has now.... Here are the new parts I've made....



I made an extended valve front end to move the O-rings in front of the roll-stamp on the 2260 tube.... It has a lot larger bore, and is 9/32" at the spring seat instead of the stock 1/4".... The valve spring has been enlarged at one end to 9/32 to increase the flow as well.... The rear half of the Disco valve is bored out to 5/8" ID (from 1/2") to unshroud the poppet.... The flow into the valve is so much larger than out, basically the valve volume is the whole 2260 tube, from a pressure drop point of view.... I thinned out the stem of the valve poppet from 0.157" to 0.109", shortened it 0.100" for increased hammer travel, drilled the throat of the valve to 1/4", milled the exhaust port to 3/16" on a 20* angle, and rounded the corners for better flow....

The hammer has been modified by grinding a flat on the bottom to allow for the extra travel without hitting the sear.... and the cocking slot in the tube lengthened 0.100" as well.... I made a spring guide from steel which sits in the hammer and adds 11 gr. to the weight, the total is now 68 gr. instead of the stock 60 gr.... The spring guide runs in the preload adjustment screw, and provides a cocking indicator as well.... Thanks to Ribbonstone for that idea....



The tank block is the reversed style I came up with a while back, and mounts to the threaded front of the 2260 tube using a drilled out CO2 nut riding on a hollow bolt.... The aluminum bushing carries an O-ring to provide a seal past the threaded area where the tube is full thickness.... O-rings (not shown) between the parts seal everything up.... The lower part of the tank block carries a standard regulator with the bottom of the tank back towards the trigger, and right up against the bottom of the 2260 tube.... The tank acts as the forestock.... In the bottom of the block is a 3-groove Picatinny rail for a bi-pod, sling-swivel, flashlight, or laser.... On top of the tank block is mounted the barrel band.... The vertical air passage is sealed on the bottom by a 10-32 low-profile SHCS carrying an O-ring.... If desired, I can drill and tap a 1/8" NPT hole on the side of the block for a gauge to show the pressure in the plenum....

This valve is also a prototype for a .25 cal pumper I plan to build in the near future.... The port areas exceed 3/16" diameter at all points.... and is the largest I have gone starting with a Disco valve.... It can be fitted with a gauge by leaving a thicker wall in the appropriate location.... and of course a pumper version will need a check valve in the front.... The pumper version will have a volume of about 5 cc....

Bob

[sholo]

... I'm hoping that the much larger plenum (the entire 2260 tube) will give me the same power (36 FPE for the .22 cal) on 1600 psi as I was getting on 1800 with the small volume between the regulator and valve it has now....

Bob

As usual Bob - awesome work!

I would think 36 FPE (2260) is easily attainable with a 13 ci bottle, considering how much you have opened up the air flow passages. On my 2260 (which I used your build as a guide) I'm getting 32 FPE from 16 gr Polymags (heaviest pellet I have...for now) and that is with the stock TP sleeve drilled out to only 5/32" - not even close to how good your valve will flow...

Todd

[rsterne]

The Hayabusa has a 1" OD tube instead of 7/8".... so the valve is physically larger.... The valve is the Hayabusa is also a two-part design, where the tube is the main valve body.... It is possible that is allowing greater flow past the poppet as there is no shrouding by the valve body.... However, the ports are essentially the same size, a 1/4" throat and 3/16" angled port and 3/16" transfer port.... It's possible the transfer port in the Hayabusa lines up a bit better, there is a slight misalignment in the 2560 because of enlarging and angling the port starting from a Disco valve.... It could also be a slight sealing issue on the 2560.... The difference in power is relatively small (about 5 FPE regardless of pellet weight)....

I do know that more power can be had from the Disco valve, however.... Lloyd Sikes (of Crosman Rogue fame) has achieved 80 FPE with .25 cal EunJin Points at 2200 psi.... What that would translate to at 1900 psi like I use in my Hayabusa is unknown, I'm guessing similar to the 73 FPE I achieved....

Bob

[Gippeto]

(damn i-phone!)

Todd

Many would agree! LMAO Go Droid and don't look back. ;)


Bob,

Nice work on the parts, looking forward to your build up. .25 pumper sounds interesting as well. :)

Was wondering about a couple things as I've a need to do a couple similar machining bits....

The weaver rail...did you make a form cutter for doing that or doing it in multiple setups? I'm giving serious thought to making the form cutter.

The 1/2-14 NPS...any tips?

Thanks,

Al

[rsterne]

After a rather long enforced break due to busy season in the Motel, I got a chance to get back to this project over the past couple of days.... I sold off some of my earlier 2260 HPA parts, which forced me to commit to the "tank under" conversion of that gun, which saw the destruction of about 100 ground squirrels and marmots this spring.... I used the tank mounting block, extended valve, and hammer spring guide from earlier in this thread, and reassembled the gun using a 13 CI tank regulated to 1600 psi and carrying a 1.8K burst disc.... The hope was that the increased plenum volume of the full length 2260 tube between the regulator and valve would allow me to achieve the same power levels on less pressure than I was using previously (1900 psi), and I'm please to say that was the case....

The initial tests were done without the spring guide (which increases the hammer weight by 11 gr.) with the following results....



As is typical with a regulated gun, the velocity plateaus if you have more hammer strike than needed for the regulator output.... In this case, there is no loss in velocity with reducing the preload one turn from coil bind, and only a 20 fps loss at 2 turns out.... That setting gives me 943 fps with 21.0 gr. H&N Baracudas (41.5 FPE), and 1000 fps (40.2 FPE) with the 18.1 gr. JSB Exact Heavies.... One more turn out drops the 'Cudas to 890 fps (36.9 FPE) and the JSBs to 954 fps (36.6 FPE), which is right on the velocity that proved so deadly with those pellets in this gun in the spring.... One more turn out, and the power level drops to 30 FPE....

The purpose of using the full length 2260 tube and reversing the tank to sit underneath it, was to greatly increase the volume of the "plenum" between the regulator output and the valve seat.... The extended front end on the valve allows more air to enter the valve than can escape during the shot, so the pressure at the valve seat drops less because of that, raising the AVERAGE pressure during the shot.... My calculations show that the air usage (33 CI at 1 bar) when the gun is tuned for 37 FPE drops the pressure to 1480 psi when the valve closes at the end of the shot, making the average 1540 psi during the shot.... That means the valve is releasing 4.9 cc of HPA to do the work.... This rifle is a .22 cal with a 24" barrel, which places the bore volume at 14.5 cc, so that air can expand by nearly a factor of three in the barrel, which should lead to reasonable efficiency.... Here is a graph of what is happening in this case....



You can see that the efficiency tracks virtually parallel to the ratio of the bore volume divided by the volume of HPA used for the shot.... This is an important piece of information I learned from Steve in NC on the Green Forum, and I thank him for that "lightbulb moment".... After doing the baseline work, I added the 11 gr. hammer spring guide, and found that I could now back off the hammer spring preload an additional 3/4 turn and still get the same velocities.... At this point I also changed to a new tin of JSB Heavies, and it turns out they were 0.1 gr. heavier, so I fiddled with the preload to bring the velocity to 950-960 fps and shot a complete string, filling to 3000 psi....



As you can see, the results are an extremely flat string, with an ES of only 12 fps over shots 2-45.... I'm still under the hex of the "low first shot after a fill" gremlin, but at 938 fps, it was only 2% below the average velocity of 957 fps (37 FPE).... The bottom line is that I had 44 shots within a 12 fps range, and 47 shots with 2.5% (24 fps).... The pressure after the last shot was 1280 psi, meaning that I can shoot 300 psi below the regulator setpoint without a noticable drop in velocity.... That shows a VERY good balance between pressure and hammer strike, which is confirmed by the efficiency of 1.12 FPE/CI.... All that remains is to do some long range testing to find the highest velocity at which the JSB Heavies will hold good groups.... and to test a few other pellets to see if any others are up to scratch....

Bob

[poil27]

played with both i phone and android , android is way bether

[rsterne]

After many months I finally got back to working on my 2560 HPA.... This round of mods is going to see an 18 CI tank instead of a 13 CI, with the regulator set as low as I can and yet achieve 50 FPE with the JSB Kings.... Ideally I would like to keep it to 1600 psi and use a 1.8K burst disc, but the way the valve is mounted in this gun can stand 3000 psi easily, so I can certainly run a higher regulator setpoint and a 3K burst disc if I need to.... I decided that this time around I would hog the Disco valve out even more, and enlarge all the ports to 7/32" (0.219") or the equivalent area.... Here are the results on the valve, with a stock one beside it for comparison....



In the first photo, the stock valve is on the left.... The port is 9/64" diameter and vertical.... Note that you can't see the valve throat at all.... The modded valve is the one on the right.... The port is 9/32" diameter and angled 20 degrees.... You can clearly see the valve throat....



In the second photo, the stock valve is on the right, and the modded one is on the left.... The drills inserted into the ports show the huge difference in the diameter and the direction of the ports.... The new valve has nearly 2.5 times the port area than the stock one.... and it is 36% bigger than it was during the last set of tests.... The valve throat was drilled previously to 1/4" (stock is 7/32"), and the stem of the poppet has been slimmed from 5/32" to just under 7/64".... That means the throat area is slightly larger than the rest of the valve ports, and over double the area of a stock valve.... The transfer port is 7/32" ID, and the barrel port tapers from a 7/32" circle where it meets the transfer port to a 1/4" long x 3/16" wide oval on the inside.... That maintains the area, while keeping the width of the transfer port to 75% of the bore size to avoid pellet loading issues....

I also had to drill the top hole in the main tube to 3/8", and also the breech.... The new transfer port is made from 3/8" brass stock, turned down to 1/4" OD on the ends and sealed with O-rings directly to the valve and barrel.... I'm not too far from being able to assemble the gun for initial testing, tethered to a regulated air supply so that I can change the pressure without pulling the gun apart....

Bob

[rsterne]

My 2260 is currently using the 18 CI tank at 1800 psi but only about 10cc volume between the regulator and valve.... That really hurts the AVERAGE pressure during the shot.... It has seen over 50 FPE, and currently detuned to 36 FPE (18.1 gr. JSBs at 950)....



The 2560 is currently using a 13 CI tank at 1600 psi and has the reversed tank block, so has the entire 2260 tube for a plenum.... and has hit 60ish FPE and currently tuned to 46 FPE (25.4 gr. JSBs at 905).... The current valve flows more than I need in .22 cal (it saw 47 FPE @ 1600) so it's moving to the 2260, and the new, bigger valve will be installed in the 2560....



I wanted to update the 2260 to the reversed tank block / larger plenum, and at the same time swap the tanks so that the .25 cal has the larger tank (since it puts out more power).... My goal is 950 fps with the JSBs in both guns at 1600 psi without wasting air.... I'm not concerned about the flow, the valve can easily deliver the power.... I'd like to keep the pressure under 1600 so I can run a 1.8K burst disc, just because (plus it will give more air available for more shots).... I know I can easily get the performance I want by increasing the pressure, but I'm in it for the challenge....

Al, the pumper project is kind of a "what if", and when I proposed it over on the Green Forum, Steve in NC said I couldn't get the efficiency required to reach my goal (1 FPE/CI, based on total swept volume).... so of course now I have to try.... *grin*.... My goal is 30 FPE in (hopefully) 10 pumps with a 392 size pump (~3 CI) in a Disco tube.... Parts are on the way (thanks, Eric).... On the Picatinny rails, I make multiple setups and passes, they are a real PITA to make.... For the "paintball" fitting, I use a 4-jaw to hold the block, bore the recess for the O-ring (to a total depth of 0.70") with an 11/16" mill (it cuts oversize to about 0.696" ID which is perfect).... I then bore the threaded portion to size (0.740" ID x 0.400" deep).... I do a clean-out groove to the thread depth (0.840") with the point of the threading tool at 0.400" in, and then do a single point thread, using a crank handle in the headstock, turning the lathe by hand (no pucker factor involved) stopping at 0.840" diam in the clean-out groove.... and lastly clean up the finish groove one more time.... Then I clean up the thread with a 1/2"-14 NPS tap (I actually have two, one plug, and one I ground down for bottoming).... If I was better at grinding threading tools and internal threading I could probably lose the taps, but I'm not.... The resulting "paintball" adapter is again, a PITA, but works perfectly....

Bob

[rsterne]

I assembled my 2560 today, but with just a fill fitting in the end of the tube, no regulated tank.... This was just to find out if I can set the regulator to 1600 psi and achieve the 50 FPE I was hoping for with 25.4 gr. JSB Kings.... I set the hammer spring preload at maximum, filled the tube to 2000 psi, and shot the first shot across the Chrony.... 1032 fps (60 FPE).... So far so good, more power than I have ever seen in a .25 cal 22XX based gun before.... I refilled the tube, reduced the hammer spring preload a turn and tried again.... 1032.... well, at least I have some hammer adjustment left, that's good.... I repeated the procedure for 10 settings, from maximum to 9 turns out, with the following results....



You will notice that for the last half of the settings I also tested the gun at 1600 psi.... I was pleased to find out that the gun will shoot at least 964 fps (52.4 FPE) at that pressure, so my first regulated trials will be at 1600 psi.... Out of curiousity, I then set the hammer spring back to maximum and filled the gun to 2900 psi.... The valve screws are high tensile screws so I know they still have a huge safety margin at that pressure.... I tried several different pellets, topping up between shots.... I then tried the more common pellets at 2400 psi as well.... Here is what this gun can do when the pressure is cranked up....



You will notice that at 2900 psi the Kings are right on the verge of going supersonic, and the lighter ones have a nice loud CRACK to them.... The last thing I tried at 2900 psi was two Kings loaded together, for a total weight of 50.8 gr.... The resulting 92 FPE put quite a smile on my face.... it's the most power I've ever got out on one of my .25 cal guns.... At 2400 psi, the gun shot nearly 70 FPE with Baracudas, and almost 80 FPE with EunJin Points.... so it packs quite a punch even at moderate pressures....

Bob

[Gippeto]

Thanks Bob....about what I'd assumed...both jobs are going to be a PITA. No way to change the 1/2-24NPS job, but am going to have a go at the form tool...if it works it'll sure make cutting weavers an easy project.

Gonna have to make me a crank handle too...a useful accessory.

Best 'o luck with yer pumper cannon too. ;)

Al