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Air Gun Home Forum Index » Airgun Smithing » New Old Project - Hayabusa PCP - Mark III Version Goto page Previous  1, 2, 3, 4, 5, 6, 7, 8, 9, 10  Next
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PostPosted: Fri Nov 29, 2013 6:33 pm Reply with quote
rsterne
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I installed the .308 barrel today and tested a few bullets and settings.... Here are the shot strings with the 118 gr. Lee which had previously produced the best accuracy in my DAQ....



The gun is very sensitive to small changes in hammer spring preload, those three curves span only one turn of adjustment.... Just shy of coil bind, the first shot is the fastest at 207 FPE, and efficiency over the 6 shots is 1.03 FPE/CI.... At one turn out, I have 11 shots averaging 184 FPE within a 4% ES and the efficiency has increased to 1.22 FPE/CI.... The first 10 of those shots are within a 2.5% ES, and 7 of them are within just 1%, with 3 in a row being identical at 847 fps.... This gun is slightly more powerful than my DAQ, and a lot more efficient at the same pressures.... As a comparison, my DAQ gets only 5 shots averaging 180 FPE at an efficiency of 0.88 FPE/CI, and that was after I tuned it.... The way I got it, it lost nearly 100 fps over the first 3 shots at an efficiency of 0.38 FPE/CI, but with no more power....

For hunting a good tune is 1/2 turn out.... The first 6 shots are within 7 fps ES (0.8%) and average 193 FPE.... The mid-portion of the shot strings with this bullet are the flattest I have ever seen in a big bore.... Just for the heck of it, I fired a few 46 gr. JSB pellets which I had upsized to 0.308" diameter and they shot between 1190-1198 fps, easily supersonic.... Talk about LOUD !!!

Bob

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PostPosted: Thu Dec 05, 2013 3:42 pm Reply with quote
rsterne
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My mold for the new Boattail bullets I designed came in a couple of days ago and I cast some yesterday.... Today I had a chance to test them in my .308 Hayabusa.... Here are the results....



Peak velocity reached at coil bind was 1022 fps (184 FPE).... I shot strings with the preload at 2 and 3 turns out, shooting 5 shot groups through the Chrony at the same time.... At 20 feet the groups were all ragged holes, most under 1/2" OD, which is decent for cast bullets.... but I noticed there was no resistance loading these very short bullets and pushed one out after chambering it and there were no marks on the bullet from the rifling.... I have a longer bolt probe which I use for pellets and installed that, and then you could feel the bullet engaging the rifling, there is a photo below....



The front band is engaged about half way long the leade, and the accuracy immediately improved.... Here is a typical group when chambered deeper....



The group measures 3/8" across the longest point, pretty tight when a single hole is 5/16".... I think these new bullets show a lot of promise.... The velocity dropped a bit when chambered deeper, but I got one extra shot and greater efficiency.... The green string above averaged 965 fps (164 FPE) with 10 shots within 21 fps (2.2% ES), starting from 3000 psi and ending at 2320, for an efficiency of 1.25 FPE/CI.... The string shot at 3 turns out (black) was 15 shots within less than 4% ES at 154 FPE and 1.30 FPE/CI, so the gun is delivering excellent efficiency with what for this gun are pretty light bullets.... I'm delighted with the way my new Boattails performed, it's going to be a frustrating wait until the spring to let them stretch their legs....

Bob

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Time for the Hayabusa .410 / .457 to take shape.... 
PostPosted: Sat Feb 08, 2014 4:07 pm Reply with quote
rsterne
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Over the last year plus I have been collecting the major parts I needed to continue the development of my Hayabusa.... From the beginning, this project was a test gun, designed to help me learn about PCPs, both regulated and un-regulated, and from .22 cal up to .45 cal.... Originally, I have developed a .22 and .25 cal regulated version, shooting pellets.... I then moved on to an unregulated version, or actually two versions, one set up for .224 cal and .257 cal bullets, and the other set up for .308 and .357 cal bullets.... During the process, the larger one ruined a Disco poppet, which was not up to the task of handling 3000 psi on a 5/16" valve throat, so development was delayed until we found PEEK as a much better material for the higher loads of a big bore airgun....

This allowed me to get to work on the largest version, which will be made as a .410 bore air shotgun, and then as a .457 cal rifle.... In order to deliver greater power, I had to make virtually all the parts from scratch, building the new gun around a 500 cc 3600 psi tank from Best Fittings in England.... The main tube diameter was increased from 1.000" OD to 1.125" OD, still 0.065" wall CrMoly tubing, which pushed the limits of safety to the maximum I am comfortable with.... The yield limit on the tube is 8,200 psi (2.3:1), and 12,600 psi at burst (3.5:1); the shear force on the three 10-32 low profile, 180,000 psi screws is down to a safety margin of 2.1:1, and the yield limit of the tube wall supporting the screw heads is only 1.4:1.... In order to guarantee I never have to worry, I fitted a 5K burst disc in the tank block to prevent the pressure (even on a messed up overfill) ever rising to the point where that became an issue.... NOTE: I am not recommending that anyone ever push safety limits to this extent.... I am very experienced with HPA, and I feel comfortable doing it, but I am working this design to the maximum I would ever do.... You can bet I will be watching the tube cradling the screw heads like a hawk (a Hayabusa?) for any sign of distortion under load during the first fill....

Anyway, I have spent the last couple of weeks machining the custom parts I needed to utilize the larger tank and main tube, and here is the first look at them....



The 250 bar 500 cc tank is about an inch longer than the 22 CI 3000 psi tank that I used on the previous versions, and it's 3/8" larger in diameter.... to accomodate the 64% increase in air crammed into it.... The main tube holds an additional 145 cc of air, bringing the total to 645 cc (39.3 CI) at 3600 psi.... The passages through the tank block are larger than the valve throat, which is 0.406" (with a 1/8" stem), and all the ports are a full 3/8" diameter, which equals the largest hole I can get through the base of a .410 shotshell where the primer used to be and still retain the wad.... and is 82% of the boresize for the .457 cal, at the limits of what can be done with a round barrel port.... I'm using the same Marauder trigger, but I had to mount it on a pad silver-soldered onto the main tube as it needed to be moved forward an inch to accomodate the 2" hammer travel.... The hammer is 2.25" long, and with the cocking handle and 5/16" spring guide (which is 5" long) weighs 225 gr. (8 oz.).... The spring is a McMaster Carr, having 31 coils of 0.072" wire, and it's 4.5" long, and takes over 36 lbs. to cock it at coil bind.... Surprisingly, with the side cocking lever, that isn't that hard to do.... you can see the long slot in the main tube just behind where the valve mounts....

The weird looking part fastened to the trigger is an enlarged version of the trigger/tank/breech mount I used on the previous versions, but all new parts because everything is bigger.... It took me 2 full days to make.... The top of it has two tapped holes to accept the front breech screws, tying everything together rigidly.... The RVA has a 9/16"-18 NF adjusting screw that allows me to change the hammer spring without stripping the back of the gun apart.... It has well over 1/2" of travel outward from coil bind, and as the spring only has 0.2" of preload at coil bind, that should be plenty of adjustment.... The spring guide, incidently, is free floating, but captured between the hammer spring and the hammer by a small conical flange on the front of it.... It travels with the hammer, so becomes part of the mass.... If I want to lighten the hammer, I can replace it with a Delrin one.... The tank block has mounts for the 5K burst disc (visible) and on the other side mounts for the 4,000 psi gauge and male Foster fitting.... The tank mount is made from an 18 mm x 1.5 mm bolt drilled out to 7/16" ID for the airflow, and a vertical air passage through the block of the same size is sealed on the top with a flush fitting 1/4" NPT plug.... When assembled, everything drops into the same stock I used on the previous versions, even though the only shared part is the trigger, everything else is new....

I still have the valve spring mount to make, and then all the parts above can be assembled and pressure tested.... Once that is done, I can get on with the challenge of chambering and porting the barrels and making the breech to hold them.... I'm pretty excited to see this project coming along so nicely, and I'm especially anxious to find out how the .410 shotgun version will work out....

Bob

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PostPosted: Sat Feb 08, 2014 10:25 pm Reply with quote
rsterne
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Just to put this information into this thread.... I posted this a while back....


Over this winter I plan to continue with the development of my Hayabusa project gun by building a .457 rifle and a .410 shotgun version.... It is my hope for them to share a common valve, main tube and hammer, and a 500cc 250 bar (3625 psi) tank.... They will, of course, have different breeches.... Here is the ammo for the .410....



....

The shell has been shortened from 2.5" to 1.75" and the primer hole drilled out to 3/8".... The shot cup holds 223 grains of #7.5 shot (0.51 oz) full to the top (about 180 pellets).... My target velocity is 950 fps, but that works out to 450 FPE, which even with 3600 psi may be a stretch....

Bob

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PostPosted: Sat Feb 08, 2014 10:25 pm Reply with quote
rsterne
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and some more previously posted....

An interesting thought came to me today when I was thinking about how to Chrony the shotshell loads without hittting my Chrony.... I had some OOO Buckshot which measure about 0.36", and found out that they are a perfect fit inside the shotcup.... it still loads normally into the shell....

....

They weigh just under 70 gr. each, so the total, is only 5% less than a 1/2 oz. of birdshot.... Just out of curiosity I also tried a .357" bullet and it also nestles nicely in the shotcup.... so if I want to have only a single projectile for Chronying I could get some 220 gr. bullets as an alternative.... However, I would think the dispersion on just three roundballs would be so slight that the chance of hitting my Chrony would be no worse than usual within 10' or so, and that should get it away from the muzzle blast no problem....

Incidently, the retained energy of EACH roundball is 120 FPE at 30 yards starting from 950 fps at the muzzle if I can push them that fast.... Three of them would make a heck of a mess of whatever they hit....

Bob

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PostPosted: Mon Feb 10, 2014 11:28 am Reply with quote
rsterne
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I got the bottom end assembled and pressure tested overnight....



I filled it to 4000 psi, which is about 10% more than I will ever be using, and no sign of the tube yielding around the heads of the mounting screws for the valve and tank block.... which should be the first place to show any yield problems.... I left it overnight and it lost about 300 psi, there is a very tiny leak in the valve O-ring.... I used a 70D for the first test, replacing it with a 90D will cure that problem.... I was VERY pleased with the PEEK valve, it didn't leak even at only 500 psi....

Bob

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PostPosted: Tue Mar 11, 2014 6:40 pm Reply with quote
oddtodd
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God Bob,That thing is evil looking! You going for the mad max look? lol I am on the edge of my seat for chrony results!

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PostPosted: Tue Mar 11, 2014 7:43 pm Reply with quote
rsterne
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It won't look so nasty once it has a breech and barrel on it.... *LOL*.... ?The tube you see above the tank is the main tube that holds the valve and hammer.... I've been back working on this project the last couple of days, chambering the barrels.... Next up to make the breeches and bolts....

Bob

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PostPosted: Tue Mar 11, 2014 7:53 pm Reply with quote
oddtodd
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Oh I know the barrel and associated hardware isn't on it, but wood, black and polished aluminum? Definitely post apocalyptic looking. lol It looks cool. Like I, frankenstien meets van helsing. lol

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PostPosted: Thu Mar 13, 2014 4:54 pm Reply with quote
rsterne
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I got back to working on the Hayabusa the last couple of days and got the breeches roughed out.... I decided to make two, one for the .410 shotgun and one for the .458 rifle, as there were too many compromises to make to fit the rifle barrel in the shotgun breech.... Sean supplied me with a bar of aluminum long enough for two, so I cut a couple of 9" pieces and set up the mill to reduce then to the proper dimensions and machine the groove along the bottom for the main tube.... Here is a photo of one of them at this point....



I had a LOT of material to remove, and it took me the better part of two days.... I had to remove 1/8" from the width and 3/8" from the height, and then when I machined the groove I didn't have a 1.125" ball mill, so I used a 1" and then took extra passes off center to get a near perfect fit with three points of contact, the center and both edges.... One of the reasons it took so long was that my milling attachment on the lathe only has 6" of crossfeed and the breech is 9" long, so I had to do the machining in two setups for each dimension.... I then laid out the location of the bore and drilled it from both ends and the 3/8" pilot hole met perfectly in the middle.... The other breech is finished to the same stage except I haven't drilled the through hole yet....

I have machined the chambers in both the shotgun and rifle barrels and sleeved them up to 3/4" OD (they were only 5/8") to make them large enough to accept a 1/2" OD x 3/8" ID transfer port.... More to come soon....

Bob

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PostPosted: Sun Mar 23, 2014 11:05 am Reply with quote
rsterne
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Not quite finished the breeches, but I've made quite a bit of progress in the last 10 days....



The longer breech in the background is for the .410 shotgun, capable of loading a 2" long shell.... It is likely that I can use the shell at a length of 1.75" but I left enough length for an extra base wad behind the shot cup in case the seal isn't good enough with just the plastic cup at airgun pressures.... The breech in the foreground is for the .457 rifle version.... I could have shortened the loading port and the breech another half inch, but there was no reason to.... The boss on the front is for a 1" OD shroud to put the barrel in tension to stiffen it.... The long slot in the bottom of the breech, in front of the bolt slot, is for the cocking handle.... Yes, it really does have 2" of hammer travel.... for the 8 oz. hammer....

The next job is to make the bolts and finish machining the barrel ports.... then machine in the scope mounts on the top of the breeches.... The rifle is getting a dovetail as usual, but the shotgun is going to have a Weaver mount for a wide-screen red-dot.... I haven't decided yet if it will be in front of the loading port or behind it.... I may put a Weaver/Picatinny rail both places if I don't get lazy / in a hurry....

Bob

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PostPosted: Sun Nov 30, 2014 2:31 pm Reply with quote
rsterne
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I finally got back into the shop to finish off the breeches for the Hayabusa Mk.3.... Here they are with the barrels installed.... The .457 rifle barrel is 30" long, the .410 shotgun barrel is 25" including the poly-choke....



In this photo, you can see the basic differences in the breeches.... The .457 rifle (top) has provision for a shroud, and a shorter loading port, and a dovetail for a scope.... The .410 shotgun (bottom) is longer overall, with a longer loading port to accommodate the shotshell, and a Picatiinny rail forward of the port for mounting a Holosight....



The third photo shows the bottom and side views, with the monster transfer port visible.... It is 1/2" OD with a 3/8" ID and the flow-though bolts have the same size passage....



The next steps are a cocking handle for the hammer (you can see the clearance slot in the breeches, below the loading port), make the transfer ports (from 1/2" Teflon rod), strip the valve out to chase a leak, and it will be ready to assemble and test.... My biggest concern at that point is assuring I have an adequate backstop....

Bob

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PostPosted: Sun Nov 30, 2014 7:20 pm Reply with quote
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After over two years of planning and a year of building, the Hayabusa .410 Shotgun is together for the first time....



The only parts carried over from the original Hayabusa are the stock and the trigger group, and the overall layout.... It uses a 500 cc 250 bar (3625 psi) tank mounted in one of my reverse tank blocks, feeding a 1" ID plenum that adds another 140 cc for a total of 640 cc (39 CI) of air on board.... The main tube, hammer, valve, and tank are shared with the .457 cal rifle version, which has its own breech, as detailed above....

I spent a lot of today calibrating the Poly-Choke, which was missing the markings for the various choke positions.... I made a steel plug gauge which started at 0.410", adjusted the choke until the fingers just dragged on the gauge, marked the choke for Cylinder bore, turned the gauge to 0.406", marked the Improved Cylinder position, turned it down again to 0.402" for Modified and marked that, and then turned it down to 0.395" for Full Choke and marked that position as well.... Now you just screw in the sleeve to the appropriate mark and voila, the choke you need.... I also made and installed the cocking handle for the hammer, before assembling the gun for the first time.... It weighs just a couple of ounces under 10 lbs. complete with the sight.... The only thing I have left to make is the transfer port seal....

Bob

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PostPosted: Wed Dec 03, 2014 8:56 pm Reply with quote
rsterne
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Today I took the valve out, replaced the 70D O-ring that had a slow leak with a 90D, filled the gun from my new Great White, took out my hearing aids, put in my earplugs, and fired the first shot.... Yup, it's pretty loud!.... I had the hammer spring preload at maximum, and at 3600 psi it was just under 800 fps with three 000 Buck.... Not as strong as I was hoping for, but nearly 300 FPE, the most powerful shot I have ever had from an airgun.... I fired a few shots and examined the plastic shot cups I found down by the backstop, and they were all split or blown open through the middle of the base.... I wondered if possibly I was getting a lot of blowby, so I used a 1/4" thick fibre wad in the shell first and then the three Buckshot (no shot cup), and got more consistent and higher velocities.... The highest I saw was 817 fps, and that was 7 yards from the muzzle, so that corrects to 833 fps at the muzzle (313 FPE) at just under 3000 psi.... I got 7 shots from 3600 psi down to 2700 within 4% ES....

The disappointing part of the first tests was that I don't have enough hammer strike.... I got a very nice shot string, but I'm maxed out, and the peak is at just under 3000 psi.... This is despite having a 237 gr. hammer with 2" of travel and a spring that takes 36 lbs. to cock.... and a PEEK valve.... Before I make any changes I will try the .457 Rifle barrel with some 220 gr. bullets I have, and some roundball, just to get a baseline.... I have no idea how I could increase the hammer strike if I need to, to get more power....

Bob

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PostPosted: Thu Dec 04, 2014 4:22 am Reply with quote
AirGunEric
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Any idea how much the final version weighs?

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