Air Gun Home :: View topic - New Old Project - Hayabusa PCP

rsterne · Moderator

Well you knew I had to try the .25 cal barrel.... but first, a photo.... The 22CI tank will be the forestock.... Mr. Green

Here is the first string with 25.3 gr. JSB Exact Kings....

2200 psi start
964
985
1002
1020
1025 - 59 FPE @ 1900 psi
1020
1014
999
984
966
1400 psi remaining

Bigger caliber = more efficidency.... 1.45 FPE/CI (11.3 Barcc/FPE).... 1518 CI x 1.45 = 2201 FPE.... That should work out to about 40 shots at 55 FPE (25.3 gr. Kings at 990 fps).... Mr. Green

It's time to start bluing some parts and install the regulated tank.... I think it's going to stay .25 cal for the initial regulated testing.... :wink:

Bob

69Hotrod69 · Veteran Member

Very nice! It's gonna look great with the tank on.

yourdaddyjoe · Supporting Member

Workin' on that Cal. for ya bud... Check your email... Wink

yourdaddyjoe · Supporting Member

Bob, we are going to have to start the Crosman Uber Cool Club just for you!

broommaster2000 · Moderator

Isn't a club with one member a lil boring? Razz

rsterne · Moderator

Tested a few more .25 cal pellets today.... Here are the results for the peak velocity recorded....

Beeman Laser 17.3 gr. - 1162 fps - 51.9 FPE (at about 2100 psi)
H&N Field Target Trophy 19.3 gr. - 1133 fps - 55.0 FPE
JSB Exact King 25.4 gr. - 1025 fps - 59.0 FPE (at 1900 psi)
Benjamin Domed 27.8 gr. - 983 fps - 59.7 FPE
H&N Baracuda 30.9 gr. - 949 fps - 61.8 FPE
EunJin Domed 35.2 gr. - 909 fps - 64.4 FPE
EunJin Pointed 43.2 gr. - 830 fps - 66.1 FPE (at only about 1600 psi)

As is typical when you don't change anything except the pellet in a non-regulated PCP the pressure at which the peak velocity is generated drops as the pellet weight increases.... Based on these results, I need a heavier hammer spring to maximize the FPE with the heavier pellets.... I would think that about 880 fps is within reach at 2000 psi with the 43.2 gr. EunJin Pointed.... That would be about 75 FPE.... I have no doubt that this gun will be in the 70-80 FPE catagory with heavy pellets with the right hammer spring.... Cool

Bob

rsterne · Moderator

I got my heavier hammer springs in and tried them out yesterday.... I ended up using one that was 2.00" long and 0.300" OD made from 0.045" wire (instead of the 0.040" wire I use on my modded Discos).... The velocities, as expected, increased, and the velocity now peaks at 2000 psi with the JSB Kings and Baracudas, 2200 psi with light pellets, and 1800 psi with the heaviest pellets.... Here are the results with the hammer spring just shy of coil bind....

Beeman Laser 17.3 gr. - 1201 fps -55.4 FPE
H&N FTT 19.3 gr. - 1165 fps - 58.2 FPE
JSB King 25.3 gr. - 1061 fps - 63.3 FPE
Benjamin Domed 27.8 gr. - 1024 fps - 64.7 FPE
H&N Baracuda 30.9 gr. - 983 fps - 66.3 FPE
EunJin Domed 35.2 gr. - 939 fps - 68.9 FPE
EunJin Pointed 43.2 gr. - 867 fps - 72.1 FPE

Over 1200 fps in .25 cal, and over 72 FPE is pretty satisfying for a home-brew airgun.... Mr. Green

.... The efficiency with the JSB Kings is about 1.06 FPE/CI (not bad, but I wanted better), so I decided to start backing down the hammer spring as I don't want over 1000 fps anyway.... Here is what happens to the peak velocity and efficiency as I do that.... The last number in each line is the projected number of shots from a 22 CI tank regulated to the pressure where the peak velocity occurred....

Maximum - 1061 fps @ 2000 psi - 1.06 FPE/CI - 25 shots
-0.5 Turn - 1043 fps @ 1900 psi - 1.10 FPE/CI - 30 shots
-1.0 Turn - 1030 fps @ 1800 psi - 1.15 FPE/CI - 35 shots
-1.5 Turn - 1010 fps @ 1700 psi - 1.23 FPE/CI - 42 shots
-2.0 Turn - 979 fps @ 1600 psi - 1.31 FPE/CI - 52 shots

Note that by dropping the velocity only 9% the shot count more than doubles.... Shocked

.... At 1800 psi and 2 turns out the velocity is 950 fps (51 FPE) and the efficiency should actually be slightly higher than 1.31 FPE/CI as that was taken over a 10 shot string, and the efficiency is always better in the first half of the string.... I would expect to get about 50 shots with my 22 CI tank regulated to 1800 psi with that state of tune.... and I will have the flexibility to increase the velocity should I choose to.... I will probably test a lighter hammer just to see what happens, but the current plan is to set the regulator to 1800 psi when I assemble the gun for the initial regulated tests.... I had originally planned to use 2000 psi, but this gun breathes so well that I can get the power I want with a lower pressure.... That means I get 20% more air available in the tank above the regulator setpoint.... Mr. Green

Bob

yourdaddyjoe · Supporting Member

Awesome Bob!

rsterne · Moderator

I tested the lighter hammer and it was a few fps less, as expected.... so the gun will stay with the heavy (92 gr.) hammer.... I stripped the gun down completely to blue the steel components and then assemble it with the tank for the first time.... I had to rebuild the regulator to reduce the pressure to about 1800 psi.... After cleaning the bolts, barrels, and main tube carefully I blued them using Van's Gun Blue and I was very happy with the nice even, deep colour.... I cleaned the barrels, oiled them, ran a couple patches through them until they came out clean to just leave a preserving film of oil.... and then carefully assembled the gun, using all the appropriate lubes.... I did a pressure test which seems fine, fired it once just to make sure it worked, and then rushed in to get some photos....

As you can see, I have a .22 cal and bolt that will fit, and MRod clips for both calibers.... The BiPod is a Leapers that fits on the short Weaver rail on the tank block, along with a sling stud swivel.... Both barrels are Lothar Walther, standard rifling, choked.... I have some polygonal rifled barrels coming for comparison purposes....

The final weight came in at right at 8.5 lbs without the bipod and scope.... I will be fitting a Bushnell 5-15X Legend and then I'll be ready for some seriouis testing.... This project was conceived almost a year ago, and machining started the beginning of 2011, so the gun is now about 9 months from the start of making chips to completed.... It's been quite the gestation period.... but all in all, I'm pretty happy with my "first born".... Mr. Green

Bob

rsterne · Moderator

I finally got back to testing today.... It was a lot of fiddling around with spring and hammer settings, and then using the velocity adjuster to get close to where I want to be.... I tried two springs, the 2.00" long 0.045" wire, and also one that is 1.75" long 0.051" wire.... With each spring set at maximum preload (just shy of coil bind) I then adjusted the hammer fall distance to see if there was a maximum velocity point.... To my surprise, with the short heavy spring I had to reduce the hammer fall by 9 turns (3/8") to get the maximum velocity.... That told me that a 1.75" spring is too short, it's running out of push in the last part of the hammer stroke.... I then did the same thing with the longer, lighter spring, and the best setting was 3 turns (1/8") from maximum fall.... The difference in fall distance was the same as the difference in spring length.... That means that if I had a longer spring (2.25") I could take advantage of all the hammer travel I have available.... if I wanted more power.... I'll be ordering a longer spring for when I try larger calibers at a later date....

I then started playing with the velocity adjuster.... This is a screw on the side of the breech that chokes up the transfer port.... It has 6 turns of travel from fully closed (just two slits for the air to pass through either side of the screw) to fully retracted clear of the port.... Since the end of the screw is hemisperical, when retracted there is a hollow in the side of the transfer port which likely creates some turbulence and increases the volume.... Therefore I was not surprised that the velocity actually increased as the rounded nose of the screw started to enter the transfer port.... What DID surprise me was that the maximum velocity occurred with the screw about 2.5 turns in from full out, ie nearly half closed.... In fact, there was no consistent difference in velocity between 3 turns out (the mid point) and 4 turns out.... I set it at 3.5 turns out and turned my attention to the hammer spring preload, as the velocity was now firmly over 1000 fps with the 25.3 gr. JSB Kings....

I then turned my attention to the hammer spring preload.... I backed it out a turn and the velocity settled in at about 950 fps.... This is less than I was getting in the unregulated version at 1800 psi (the regulator setpoint pressure).... and I was at a loss as to why.... I took out the hammer spring and measured it, and it turns out it has taken a bit of a "set" as it now measures about 1/16" shorter now than when I first installed it.... That would account for the velocity loss.... I still had more power than I needed, so it doesn't matter, of course.... When I started testing velocities through the range of pressures, I found that after the pressure fell below the regulator setpoint the velocity started increasing, up to nearly 1000 fps, before falling back to 950 fps at only 1400 psi.... This is a sure indication that the gun can breathe too well for the hammer spring and regulator pressure.... I cranked the velocity adjuster in another turn, then a half turn more to only 2 turns out, and the velocity fell to the low 900s.... Then I cranked the hammer spring in a half turn, and it bounced back up to about 960 fps.... Now when the pressure dropped below 1800 psi (the setpoint), it only went up to the high 960s, dropping back below 950 at 1500 psi.... Now we're getting somewhere.... Mr. Green

By now I had burned through about 500 pellets and my SCUBA tank was down to 2600 psi.... However, I had collected enough information to figure out that the efficiency was stll close to the previous testing at about 1.3 FPE/CI.... The velocity is between 950 and 960 fps while the pressure in the tank is over 1800 psi.... below that, it rises about 10 fps before falling back down to 950 at 1500 psi.... This give me 1500 psi of usuable air in the 22 CI tank which works out to 2276 CI.... That should translate into roughly 2900 FPE.... The average velocity is about 958 fps which works out to 51.6 FPE.... That should give me over 50 shots per fill....

Bob

rsterne · Moderator

I got a slightly longer hammer spring to try.... 2.25" long and 0.045" wire.... As you lengthen a spring with the same OD and wire size the spring rate goes down slightly but the maximum load stays about the same, but at more travel.... I made a new velocity adjusting screw with an integral spring guide.... I picked up a bit of velocity, and the combination of the longer spring and the guide made the cocking significantly smoother.... Anyway, after fiddling with all the adjustments to get the maximum I could, I got the following numbers, regulated at 1900 psi....

JSB King 25.3 gr. - 1038 fps - 60.5 FPE
Benj. Domed 27.8 gr. - 998 fps - 61.5 FPE
Baracuda 30.9 gr. - 958 fps - 63.0 FPE
EunJin Dome 35.2 gr. - 922 fps - 66.5 FPE
EunJin Point 43.2 gr. - 857 fps - 70.5 FPE

These figures were more than I want, and the gun was an air hog at maximum setting.... so I tried two routes to detune it.... I tried using only the hammer spring preload (out 2.5 turns), and I got 47 shots averaging 985 fps down to 1500 psi.... However, the velocity below the setpoint climbed to 995 fps, whereas the velocity above the setpoint had a low of 978 fps and a high of 989 fps.... The total spread was 17 fps.... I then tried a combination of hammer spring and restricting the transfer port.... I backed off the hammer spring until the velocity dropped to 1000 fps (1.25 turns).... Then I turned the screw on the transfer port in 2 turns to reduce the velocity to an average of 968 fps (52.7 FPE).... The velocity no longer climbed when the pressure dropped below the setpoint, it stayed in the same (narrow) range down to 1700 psi (200 psi below the setpoint) before dropping.... The lowest velocity was 964 fps and the highest 972 fps (only an 8 fps range).... I got a total of 43 shots starting at 3000 psi and shooting down to 1700.... for a total energy of 2266 FPE.... The pressure drop of 89.7 bar on a 22 CI tank works out to 1973 CI of air used.... for an efficiency of 1.15 FPE/CI (14.3 Barcc/FPE).... I really like this method of tuning as I can easily adjust the velocity from 1000 fps downwards to find the sweet spot with the 25.3 gr. JSB Kings for accuracy.... by simply turnng a screw on the side of the breech....

I'm very happy with the way the Hayabusa is tuned at the present time.... I hope I can get out to our Camp to test the gun at longer ranges, test various pellets for accuracy, and try fine tuning it.... before the snow flies.... Rolling Eyes

Bob

rsterne · Moderator

I've been busy with other projects, but figured I better drag out the Hayabusa and do some more work on it, based on what I have learned over the past few months.... I pulled the back end of the gun apart, drilled out the hammer to 3/8" ID, drilled out the RVA, and fitted the hammer spring from a QB.... I now have plenty of spring power so I have lots of adjustment instead of running out of room on the RVA with the shorter springs I had been using previously.... The gun doesn't have any more power with the lighter pellets, but it did pick up a bit with the heavier ones.... I'm still running the gun regulated at ~1900 psi, and here are the results at various hammer spring settings....

I'm now up to 73 FPE with the EunJin Points, and over 60 FPE with the JSB Kings, at maximum power.... However, the gun set up that way is an Air Hog.... I can dial it down 4 full turns on the RVA without losing any velocity and double the shot count, still at 60 FPE with the Kings and 62 FPE with the Baracudas.... Set that way, I would get about 25 shots per fill.... Once again, I found that giving up just a few fps below the plateau works wonders with the air consumption, however.... Backed out one more turn, I only lost 30 fps, and gained another 10 shots or so.... You can see the effect on the Efficiency that the RVA has using the dotted line on the graph above....

This setting (5 turns out on the RVA) formed the basis for additional tests, starting from 1004 fps and an efficiency of 0.96 FPE/CI with the JSB Kings.... The first thing I did was started restricting the transfer port with the adjusting screw on the side of the breech.... You can see the results in the dashed line on the graph.... The first two turns made no difference, I assume because the small protrusion of the ball shaped end on the screw, although restricting the port, was smoothing the flow compared to when it was fully retracted.... At 3 turns in, the velocity dropped to 962 fps and the efficiency jumped to 1.19 FPE/CI.... At that point, I'm getting over 50 shots at 52 FPE per fill, and I can shoot down to 1500 psi before the velocity drops below 950 fps.... Once I get a chance to do some accuracy testing at longer ranges, I can adjust the velocity from 1000 fps down to as low as 600 fps by simply turning a screw in the side of the breech....

When I made the hammer for this gun, I made the throw (hammer travel) adjustable using the adjusting screw from an MRod.... You reach it from the back with a long allen key, by removing the RVA adjusting screw.... With the spring preload at 5 turns out, there is very little static preload on the hammer spring.... As you lengthen the nose of the hammer by turning in the adjusting screw, you reduce the distance the hammer travels, reducing it's momentum.... However, you increase the static preload on the hammer spring because the resting position of the hammer moves back.... These two effects cancel each other out (at the spring preload tested) for about the first 4 turns on the throw adjuster.... and the velocity stays constant.... I did notice, however, that the first shot in the string had a slightly lower velocity, and that difference increased as I reduced the hammer travel (and increased the spring preload).... As I further decreased the hammer travel, the velocity did begin to drop.... By the time I moved the adjustment 10 turns (0.42"), the velocity had dropped to 920 fps, but the first shot was under 900 fps.... I did not check how the efficiency changed as I adjusted the hammer throw, because the inconcsistency of the first shot bothered me.... I ended up backing up the adjuster to go back to the full hammer travel I started with....

My base settings are: Full hammer travel.... 5 turns out on the RVA.... and 3 turns in on the Velocity Adjuster.... That has me sitting at an Efficiency of 1.19 FPE/CI (13.8 Barcc/FPE) giving 50 shots at 52 FPE (962 fps) with the JSB Kings.... With 1 turn on the velocity adjuster either way, I can change from 900 fps to 1000 fps, which should enable me to fine tune the accuracy.... I can't wait until the snow melts and I can do some long range testing....

Bob

SMP · Silver Status Member

I can't wait for you to get out and do some some long range shooting.

So using some basic pipe physics do you think the velocity of the fluid column is increasing as you decrease the port size....Thereby the efficiency is going up?

rsterne · Moderator

Well if the pellet velocity stays the same, then in theory the velocity in the transfer port must be going up if the area is smaller.... When it's all the way open, however, the nose of the restrictor is flush with the inside of the port and there is an annular, sharp sided hollow around it.... a source for turbulence I assume.... When it is closed 1/3rd of the way (on the diameter) the total area would be a bit less, but I'm thinking the airflow is going smoothly around the tip of the restrictor instead of eddying.... It looks like this at the point it starts having an effect on the velocity....

From what I understand, the MRod has the same thing, the first turn or so into the airstream does nothing to the velocity....

Bob

rsterne · Moderator

It's been nearly a year since I worked on my Hayabusa.... During that time I've learned a lot, and I hope to apply some of that knowledge to this project over the next few weeks.... Here is the gun in it's current form.... It's a .25 cal repeater, regulated to 1900 psi, and shooting 25.4 gr. JSB Kings at 960 fps.... It gets about 50 shots per fill.... I also have a .22 cal LW barrel that interchanges with the .25 cal LW in the same breech....

For a while now, I have had several other barrels for further development, a .30 cal and 9mm Lothar Walther, a .457 liner from TJs, and even a .410 shotgun barrel with polychoke.... but no time to work on them.... A few months ago, I came across some information about new bullets from Holland that are being used in Benchrest competition and doing a spectacular job, with groups at 100 M (110 yards) as small as 12 mm (under 1/2").... They are a .224 cal version of the classic .22LR bullet, are made by RWS, and appear to be very close to their R-50? target bullet.... The barrel required is, of course, slightly larger than the 0.217" airgun barrel, with a faster twist.... They are using a .22 Hornet barrel with a 1 in 14" twist.... SeanMP and I decided to do a pair of guns.... Sean's is going to be a new, scratch built design, while I'm going to use my Hayabusa as a base, but unregulated, and with a new breech, valve, hammer, and other changes.... In fact, about the only parts carried over to the new gun will be the trigger assembly and the stock, plus the ring assembly that holds the back of the tank and the front of the trigger.... The Mark II Hayabusa will look almost identical, but the changes are vast, and won't occur overnight....

I ordered two .224 liners from TJs with a 1/2" OD, and had them shipped direct to Sean.... He ordered 2000 bullets from Holland, plus two pieces of 1/2" ID x 5/8" OD Carbon Fibre tubing to stiffen the barrels.... We each purchased a .22 cal Hatsan Air Stripper, and Sean did all the machine work on the barrels.... He crowned and threaded the muzzle 1/2"-20-NF for the strippers, glued the CF tubes in place with Accraglas, and machined the chambers and barrel ports.... In addition, he lapped and polished the bores to perfectly fit the bullets.... I received my barrel and bullets yesterday, and here are the photos of his work.... GORGEOUS !!!

The barrel port is a bit unusual.... I designed it so that the area was the same as the bore, but the width was only 75% of the bore size, to prevent damaging the bullets on loading.... The transfer port will be 0.219", and the barrel port starts that size and becomes oval, ending up 0.160" x 0.312" at the bore.... The back of the port is vertical, and the front is angled forward about 45*, maintaining a constant area and smoothing the flow to the base of the bullet.... The valve will have matching areas throughout as a lot of flow is needed to get the performance required....

The goal for these rifles is daunting, but we know it's attainable as they are doing it in Holland with the "Sinner" target rifles.... We need to duplicate the performance of .22LR standard velocity target rounds, or nearly so.... The goal is a velocity with the 41.5 gr. bullets of between 950 and 1050 fps.... for an FPE of 83-102 FPE.... and we need to do this with a 3000 psi fill, at least I do, because that is the pressure rating of my 22CI tank.... My onboard air volume will total about 475 cc, and 110-115 cc of that will be "on deck" and available for the shot in the main tube, which is open directly to the valve seat.... That will keep the pressure drop during the shot to a minimum.... I want to achieve a 5 shot string with the onboard air, if possible.... These guns are usually shot while tethered to a SCUBA tank or a regulated SCBA tank....

The next step is to finalize the design and dimensions, and then I can start making chips.... I hope to be able to finish the gun before the Motel gets busy again in the late spring.... My thanks to SeanMP for the beautiful job on the barrel.... I hope to do it justice....

Bob