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

rsterne · Moderator

It's finally time to start making some chips.... I spent a couple of days designing the breech and came up with a design that will work for all four barrels from .224 to .9mm.... The .224 and .257 will share a breech with a 1/4" loading tray and the .308 and 9mm will share a second one with a 3/8" loading tray.... The design for the tank block was done a year ago, so it was just a matter of printing it off, double checking it and making a few detail changes and notes, and then machining it.... Yeah, well it sounds a lot easier than it was.... It took me the entire day just to make the tank block, and I had to finish it after dinner.... Here it is....

The tank mount is the threaded portion of a 5/8"-18 NF Grade 8 bolt drilled out to 3/8".... The tank (sans regulator) seals directly to the rear face of the block with an O-ring.... The stub that goes into the 1" OD x 0.065" CrMoly main tube is located by three high tensile 10-32 low profile SHCSs and sealed by two O-rings.... The tank and tube nearly touch.... The larger hole in the stub is the air passage (9/32") which is larger than any of the ports I'll be using so basically all of the 475 cc of air is available to keep the pressure up at the valve seat during a shot.... The 1/4-20 NC tapped hole above it is for a long threaded rod that carries the valve spring.... On the left side of the block is a 3000 psi gauge (upper hole) and a male Foster fitting (lower hole) and on the right side is a 5K burst disc.... The vertical transfer hole is plugged on top with a flush 1/8" pipe plug.... The recess on the top front with the two 6-32 holes is for mounting a barrel band, and on the bottom is a 3-slot Picatinny rail....

Hopefully tomorrow I'll get to start on the breeches....

Bob

rsterne · Moderator

Well, it took three days to machine two breeches.... and I still haven't done the bolts or bolt handles.... They did, however, turn out very nice....

The two breeches are virtually identical, with the following exceptions: The loading tray (and the forward section of the bolt) is 1/4" for the .224 / .257 cal breech (the rear one), but 3/8" for the .308 / 9mm cal breech.... the through hole above the 3/8" transfer port recess is 1/4" for the smaller cal. breech and 9/32" for the larger (with room to go to 5/16" in a 7/16" TP).... and the slot to clear the cocking lever allows for a 1.25" stroke for the .22/.25 cal and 1.5" hammer travel for the .30/.35 cal.... That is where the lower part of the breech is machined away in front of the bolt slot and behind the loading port to clear the cocking handle which will be a piece of 1/4" steel rod threaded into the hammer near the front.... It will stick out through a slot in the side of the main tube at a 40* angle upwards.... When cocked, it will be just ahead of the "closed" bolt handle (angled downwards at 25*), forming an "X".... This idea is borrowed from my DAQ and works very well, "falling readily to hand"....

The barrel is secured with three 8-32 setscrews against the 5/8" OD portion, the rear one on the top and the front two on an angle.... The barrel is sealed into the breech both sides of the transfer port hole with O-rings.... The breech is secured to the main tube with a single 8-32 bolt at the rear and two 6-32 bolts which screw into the tank band / trigger mount at the front, making for a very rigid assembly.... Next up is to make the bolts and handles and then move on to making the valves and hammers.... After that, I still have to do all the machining on 3 of the 4 barrels, including turning to fit the breech, chambering, porting, crowning, and threading to accept a Hatsan Air Stripper.... I takes longer to do multiples of everything, but in the long run it saves setup time on the lathe.... Stay tuned....

Bob

ZipSnipe · Veteran Member

Nice work!! Are those aluminum? And will you be anodizing them?

rsterne · Moderator

I spent more time over the last two days repairing machinery than making parts.... The switch on my lathe burnt out for the umpeenth time (I haven't been able to find anything that will stand up in this hick town).... My local supplier found a 12V 50A switch in stock and told me something interesting.... Apparently UL / CSA removed the AC rating on most switches a while back.... This switch used to be rated at 125V 20A, and they haven't changed the switch.... They use it on a 1 HP motor there, so I figured it can't be any worse than what I've been using.... The problem was that it was too deep to fit in the cavity on the top of the lathe, so I had to make a 3/4" deep plate with a 1/2" deep cavity so that the switch mounts 1/2" higher.... Looks kinda cool, I hope it lasts.... While I was at it I lubed, checked, and adjusted everything on the lathe as well....

The other job was to replace a broken handwheel on my horizontal bandsaw.... It's a Busy Bee Chinese special, and the handwheel that runs the clamping vice was plastic.... Needless to say, the hub split, and the only part that was reusable was the handle to spin it.... I made a new handwheel from a 1.5" cast iron pipe flange with a couple of adapters screwed into it to bush it down to smaller than the shaft.... I drilled it out, drilled and tapped it for a setscrew, and drilled and tapped a (metric) hole for the handle near the perimeter.... I works like a charm, and looks suitably "Coalmont" in nature.... I guess I've finally graduated from Hillbilly repair school....

Anyway, I finally got around to making the bolts for the two breeches, as below....

The front one with the handle screwed into it is for the .224 / .257 cal, while the rear one with the longer probe and larger diameter nose is for the .308 / 9mm.... On both bolts, the short smaller diameter nose section fits the smaller bore barrel (.22 cal on the .25 bolt, .30 cal on the .35 cal bolt), and the 60* taper is the transition to the O-ring size.... A matching taper inside the barrel guides the bullet into the chamber.... The shoulder on the bolt where the probe starts is flush with the back of the barrel port, so the chamber starts just behind the port, and the bullets have lots of length to align with the chamber before engaging the rifling.... The front driving band is just engaging the rifling as the rear of the bullet passes the front of the port, so the chamber is the length of the bullet from front driving band to base, plus the barrel port, plus about 0.030".... The O-ring that seals the bolt is captured between the end of the barrel and the breech, and the bullet slides through it on loading.... I really like this system for sealing the breech.... All the bullets are a loose fit through the O-ring except for the .257 cal, which is 0.007" bigger than the bolt at the driving bands on the bullet.... I think that will squeeze through the O-ring just fine, however....

I have ordered a set of 5C Collets and a square and hex mounting block set for them which will be really handy for making the valve and main tube.... Since they haven't arrived yet, I think my next step will be to make the chamber reamers for the .30 and .35 cal barrels and get the machining done on those.... Still a LOT to do on this project....

Bob

rsterne · Moderator

Over the past three days I got all the machining done on the .30 and .35 cal barrels.... The first step was to machine, harden, and temper two chambering reamers, which took me basically one day.... I had made a compromise on the design of the chambers because the 9mm has both pellets and bullets to deal with (and in fact once they become available I want to try the .30 cal JSBs as well).... This resulted in the bullets being seated further forward, which would have either required a long chamber made for the bullets (and the pellets not engaging the rifling when chambered) or a short chamber made for the pellets (and the bullets would be hard to chamber).... My solution was to cut off the probe on the bolt and drill and tap the nose 8-32 and make two probes different in length by the recess in the back of the pellet, which is 0.200".... Here's what the bolt now looks like...

Now I could optimize the chamber for the bullet and the pellet would also seat against the leade by using the longer probe....The next step was to turn the breech areas to size and chamber the barrels.... I then reversed the barrel in the lathe, crowned it, and threaded the muzzle 1/2"-20 NF to accept a Hatsan air stripper.... I will have to drill out the brass stripper portion for the larger bullets, but there is lots of meat there.... Once the lathe work was done I machined the barrel ports.... Here is a photo of the machining on the barrel ends....

The main portion of the barrel that fits into the breech is 5/8" diameter, and then it's shouldered down to 1/2" where the port is.... The larger O-ring is captured between the shoulder on the barrel and the internal shoulder in the breech and is under slight compression.... The smaller O-ring is captured between the end of the barrel and the end of the breech bore, also under slight compression, and it also serves to seal on the outside of the bolt, which slides through it.... I've used this arrangement before, and I really like it.... You can vary how hard the O-ring grips the bolt by sliding the barrel back a thou or two.... The barrel port in the 9mm barrel is 0.281", nearly 80% of the bore size.... I couldn't go quite that big on the .308 but I wanted the same area, so the barrel port is oval.... It tapers from a 0.281" circle where it meets the transfer port to 0.250" wide by 0.312" long at the bore line, with the back of the port being vertical and the front angling forward at 20*.... This keeps the same area while avoiding loading problems.... The valve throat and ports will be optimized to work with the 0.281" transfer port.... Here is a photo of the two barrels, with the .35 cal (9mm) in the breech and wearing a Hatsan air stripper....

After completing the machining, I lapped both barrels with JB Bore Paste, followed by polishing with JB Bore Bright.... I checked the twist, and they are both 1 turn in 16", which is a little faster than what Lothar Walther had told me.... They told me all their airgun barrels were 450mm twist (17.7").... Both barrels are 28" long, the 9mm is 18mm OD and the .308 is 17mm OD....

Bob

rsterne · Moderator

I got a chance to use my new 5C Collet and the square indexing block today when I made the valves.... I turned down a piece of brass stock a bit over 2" long down to 0.862" OD which is a nice slide fit in my main tube.... I drilled one end for a 9/32" throat and a 1/8" stem and the other end for a 5/16" throat and a 5/32" stem, machined grooves for the O-rings, and then mounted one end in a 7/8" collet and machined the other for the three 10-32 mounting screws and the 30* angled port, reversed it and did the other end.... Then I just cut the piece in half and faced the back end to length to allow 1/4" maximum lift on the poppet.... They are in the fully open position in this photo....

The .22/.25 cal valve (right) uses an MRod poppet, which is 0.33" OD, so it overlaps the 0.281" throat with a seat of just 0.025".... That should be nearly perfect width, and the seat is simply flat to flat.... The port is 0.250", and the throat area minus the 1/8" stem area equals that....

The .30/.35 cal valve (left) uses a Disco poppet, which is 0.43" OD and has a 5/32" stem which I have ground down to 0.120" in the portion in the throat.... I raised the seat area 0.010" so that the seat width was only 0.025" wide past the 0.312" throat.... If I had left it flat, the sealing diameter would have been larger, making the valve harder to crack.... If the seat was made flat like in the other valve, the throat could be even larger than 5/16", so a Disco poppet might even be usuable for my .45 cal / .410 shotgun version later on.... As it is, the port is 0.281", and the throat area matches that size....

I'm very pleased with the valves, the new collet and holder system makes it a lot easier to do this job accurately.... even so, it took an entire day.... The transfer port recesses in both valves are 3/8" OD and the transfer ports will be made from 3/8" Teflon rod.... The ports will be 0.219" for the .224 cal, 0.250" for the .257, and 0.281" for the .30 and .35 cal versions.... There is enough material everywhere to go to a 0.312" transfer port with a 7/16" OD for the .35 cal if required....

Bob

rsterne · Moderator

A couple of days ago I started working on two hammers, but set them aside until today when I got a chance to drill the main tube for the valve and rear cap, and slot it for the trigger sear and cocking handle.... Once that was done I was able to lay out the location for the cocking handle on the hammers, drill and tap them, and face them to final length.... Here is the tube and hammers.... The front of the hammers is at the bottom of the photo, near the tube....

I was VERY pleased with the accuracy achieved on the valve port and mounting screws and the matching holes in the main tube.... They lined up perfectly, the advantage of the 5C collet holder.... I laid out the cocking slot from the matching slot in the .30/.35 cal breech and milled it 1/4" wide.... It is long enough to allow the hammer to hit the back of the valve (at 1/4" lift) and pull back far enough to go about 1/16" past the trigger sear for cocking.... I made two hammers, the one on the right is for the .30/.35 cal and has a travel of 1.50" and weighs 113 gr. with handle.... The one on the left is for the .22/.25 cal, has a travel of 1.25", and a weight of 94 gr. with handle.... The handle is made from a 2" long 1/4"-28 NF bolt with the head rounded.... I still have to make the spring guides, which will thread into the hammer and move with it, adding a bit more weight.... The trigger sear engages on the crosswise ledge (cut at 22* to match the sear) just behind the large flat, ie the hammer sticks out ahead of the sear when cocked.... The cocking location is 1/4" further back on the .22/.25 hammer, hence the reduced travel.... The larger hammer has a 1/4" wide slot 0.10" deep milled into the bottom to clear the sear during the shot.... The front part of the slot tapers to meet the bottom of the hammer at a 30* angle, and this allows the hammer to draw back over the MRod trigger sear during cocking.... The taper on the waist of the .22/.25 hammer accomplishes the same thing.... Here are photos showing the breech / hammer / trigger assembly....

The above photo shows the hammer in the cocked position.... The cocking handle just clears the front of the shaft of the bolt handle.... and is just inboard of the knob....

In the lower photo, the hammer is shown in the uncocked position (ie sitting against the valve stem).... You can see there is 1/4" of travel remaining to allow for the valve lift.... Both the bolt handle and the cocking handle clear the MRod stock I use just fine.... They seem to feel nice to operate, I'll know better once I put in a hammer spring.... I still have to cut the main tube to length and drill the front to mount the tank block, and then make the holder for the valve spring.... plus make the spring guides, a new, longer RVA, and then I should be ready for initial assembly and leak testing.... I hope to have my .257 barrel any day, I may wait until that is machined to fit before doing any assembly....

One other note.... I got some of the new .30 cal FX 46.3 gr. Pellets (JSB Exacts) in the mail today from AirGunSource.... I slid one through the LW barrel I have, and it was a disappointingly loose fit.... The head of the pellet had virtually no rifling marks on it, although the skirt, of course, did.... I would be surprised if they are accurate.... If they won't work in an LW barrel, JSB may have made a big mistake making a pellet that won't work in the standard size 0.308 groove 0.300 land barrels used by LW and DAQ.... Time will tell....

Bob

rsterne · Moderator

I got the last few internal parts done today, assembled the reservoir, and it is currently sitting with 3000 psi of air in it and appears not to leak.... The plenum is shorter than the regulated version by the length of the regulator, so it is now 100 cc, making the air reservoir includng the 22CI tank a total of 460 cc.... Here are photos of the sub-assembly....

I still have to make the spring guides for the hammers, do a bit of work on the RVA, and make a transfer port from a piece of 3/8" Teflon rod, but otherwise it's very close to being able to be fired.... The first tests will be with the .224 barrel which is designed to shoot the 41.5 gr RWS bullets we purchased from Holland....

Bob

ZipSnipe · Veteran Member

Looking good!! Still didn't say if you were anodizing those parts?

rsterne · Moderator

No photos today, just a brief report of the first firing.... I made a 7/32" diam. spring guide, drilled and tapped into the hammer and travelling with it.... The total weight is now 115 gr. for the .22/.25 cal one.... I measured the hammer travel at 1.20", the shallower sear engagement with the shim decreased it slightly.... I modified the RVA so that the spring guide slides through it, and to reposition the spring seat a bit further forward to allow some preload on the QB hammer spring.... With it adjusted so that the preload is virtually zero, I still have about 0.1" of adjustment before I hit coil bind.... The cocking force is about 20 lbs., similar to my DAQ....

I haven't yet fitted a transfer port or barrel, but I couldn't resist the temptation to see if the gun would at least fire.... With the adjustments as above (and no resistance on the valve outlet), I fired five shots, starting at 2950 psi, and the gun used 100 psi per shot, and MAN was it LOUD.... With the 460 cc total reservoir volume, that works out to about 193 CI of air (at 1 bar) per shot, which is about twice what it should take to achieve the power level I'm hoping for.... I am therefore pretty sure I have enough hammer strike to do the job....

I'm glad I didn't put the barrel on, as I now have to degas the gun and do the first repair.... The cheap 3000 psi Chinese pressure gauge I used (bought on eBay, straight from China) shook itself apart, and will have to be replaced.... It survived 3 shots, on the 4th shot the dial rotated about 20*, and on the 5th shot the glass and dial card removed themselves from the housing.... It still doesn't leak, I guess the vibration of firing just shook it apart.... Anyone know where I can get some quality 3000-3500 psi 1" gauges (1/8" NPT rear mount)?....

Bob

Alstone · Moderator & Site Supporter

There’s a lot of work gone into the Sub assembly’s Bob and the pictures certainly show it, I always say if it looks right then it is, and this build is a cracker.

I know you strive to get the best efficacy from your designs but the engineering does it for me. YouAreAGod

Al

rsterne · Moderator

The Hayabusa is turning out to be the ultimate in LEGO guns.... Once this round is competed, I will have .22 and .25 cal regulated repeaters using MRod clips, this non-regulated version in .224, .257, .308, and 9mm shooting cast bullets, and after that the plan is to go even bigger, I already have a .457 barrel and a .410 shotgun barrel for it....

Bob

rsterne · Moderator

I got the transfer port made, installed the barrel, and fired the first shot today.... I had about 2500 psi in the gun, the hammer spring preload was set so the spring was just touching the hammer when uncocked, which puts it about 0.1" from coil bound when cocked.... I loaded one of the 41.3 gr. RWS bullets we got from Holland, cocked it, and fired it through the Chrony.... 989 fps for the bullet, followed by the barrel, which slid to a stop against my backstop 20 feet away!.... I didn't get a Chrony reading on the barrel !!!

After I picked my jaw up off the floor, I carefully set the gun down, made sure I wasn't missing any body parts, and walked across the shop and picked up the barrel.... No damage, but three marks in the carbon fibre where it ripped out of the setscrews that were (supposed to be) holding it into the breech....

I was in complete and total shock, but examined what had happened, and realized that the carbon composite simply didn't have enough shear strength to resist the (significant) load on the barrel on firing.... I made three new marks with the setscrews, milled the CF off down to the steel, and then drilled three shallow pockets using a 3/16" drill for the setscrews.... After carefully tightening it back into place, I had no further problems whatsoever.... After an afternoon's testing the setscrews were still perfectly tight....

Well, after that initial bit of excitement, I was pleased when things settled down, and even more pleased when I filled the gun to 3000 psi and recorded 1077 fps (106.4 FPE) for the first shot at that pressure.... I'm sure I'm not the first person to hit over 100 FPE in .22 cal, but this is certainly a BIG leap for me.... I shot a string (11 shots, using 900 psi) with that hammer setting, screwed the RVA out 4 turns, refilled the gun (to 2950) and fired another string.... This time, I got only 914 fps on the first shot, and rising about 20 fps per shot for the next couple.... I then got 21 shots within a 4% ES, and then the last one just below, for a total of 25 shots using the same 900 psi as the first 11 shots.... NOW we're talking !!! .... After analyzing the first two strings, I wound the RVA in one turn, filled the gun to 2900 psi, and shot a third string.... I got 19 shots averaging 1003 fps (92.2 FPE), all of them within a 4% ES, using only 800 psi, and in fact I would expect 1 or 2 more starting from 3000 psi.... Here are the first three strings from my Hayabusa .224 cal....

So I apparently can get about 20 shots within a 4% ES without any real tuning.... The sweet spot within that is 13 shots within a 2% ES (ie 20 fps), with performance right on a par with a .22LR target velocity round.... The actual velocity I end up using will depend on long range accuracy testing this summer, but I already have a choice of an average of 1003 fps between 3000 psi and 2100 with an efficiency of 1.13 FPE/CI, or 980 fps between 2850 psi and 2050 with an efficiency of 1.27 FPE/CI.... I assume another turn out on the RVA could cut that back slightly more with even higher efficiency if desired.... I stuck my Bushnell 5-15 x 40 AO Legend scope on it, did a quick sight-in, and shot a 5-shot group, as below....

I realize this is only indoors at 20', but it does show promise.... It will be very interesting if this bullet lives up to the reputation it has in Holland for sub-MOA groups at 100M (110 yards).... The best group I have seen with it so far is 12mm (just under 1/2").... so I have high hopes.... I set out to build an airgun that will duplicate the performance of a .22LR subsonic round.... and it looks like I have succeeded.... Now I can't wait for my .257 barrel and bullet molds to arrive.... Here is a photo of the finished Hayabusa .224 cal....

Bob

ZipSnipe · Veteran Member

Love what your doing!!

I really liked what you did with the bolt probe. It got me thinking why not just tap it with a finer thread tap and then you could have an adjustable probe, sounds good to me!!

rsterne · Moderator

The thread is certainly fine enough (32 tpi).... You should probably counterbore the nose of the bolt to the smooth diameter of the probe just so that the part sticking out wasn't threaded when backed out.... You would also need to provide a "brake" so that the length wouldn't self-adjust.... That is pretty easy to do.... Drill a small cross-hole through the threaded portion of the probe, insert a piece of weed-eater line cut to length, and then thread it in.... Once you find the right length, it will partially jam the threads, leaving it adjustable, but not easily movable....

Bob