My Hayabusa PCP - The Experiment Continues

[rsterne]

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

[remtom1200]

giving 50 shots at 52 FPE (962 fps)

That is a lot of shots at 962fps!

[SeanMP]

Those bolts look great Bob. I like the double step idea for using it on two calibers. Nice

I think your guy is feeding you a load of poop on those switches. If for some reason UL was removing AC ratings from switches I would have seen a wheelbarrow load of circulars and memos...Transport Canada and TSB are pretty serious about switches. I ordered a number of AC toggles for the ship just before I was done for the year .http://www.fastenal.com/web/products...ex?sku=0715856

But when the switch died on the UtiLathe I ordered a drum switch from Princess Auto and surface mounted it right where I wanted it...And it was dirt cheap
http://www.princessauto.com/pal/prod...versing-Switch
http://www.princessauto.com/pal/prod...versing-Switch
They have heavy ac toggles as well for under $10

You'll love the 5C set. Joe finally talked me into getting a set. I can't believe how much easier life is. Even if you only use it on your drill press the $50 for a spin is worth it's weight in gold. I use it on the mill attachment on the UtiLathe

[rsterne]

Not for a while, for sure.... I'm getting Condor power from a modded Disco (over 100 FPE in .25 cal) so it begs the question why bother?.... The goal for my .257 Hayabusa is 130+ FPE, and that's nothing compared to Jack Haleys .257 "Scandalous" which has hit 310 FPE.... with a conventional "tube under" design.... He doesn't specify air pressure or bullet weight, but my guess would be 4500ish psi and 120 gr.... Certainly makes you scratch your head when you see numbers like that....

Bob

[rsterne]

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

[rsterne]

I initially drilled the .250" counterbore in the .224 barrel with a stub drill.... turned out fine, nicely centered, (I didn't go very deep) but the (118*?) shoulder was too steep and with the tightness of the chamber it was actually shaving the bullet when I pushed it in.... Soooooooo, I changed to using a center drill with a 60* taper, I had one that was 1/4" OD.... I drilled in until the taper stopped about 0.030" from the barrel port, and then polished the .250" section and the taper with 400 grit, paying particular attention to where the taper met the .224 chamber to smooth and round the edge so there was nothing to shave the bullet.... I think you might want to polish the chamber a bit more if your barrel is as tight as mine.... When I push a bullet in, it polishes the driving bands just going through the section aft of the barrel port, let alone in front of it.... It's pretty difficult to load, actually, requiring quite a lot of force to seat the bullet, especially by the time you get the base flush with the front of the barrel port.... My bolt probe is actually leaving a dent in the base of the bullet, that's how tight it is....

I was going to buy a Spin Index for the Collets, in the hope that I could mount it on my milling attachment on my lathe, but it's just too massive, so it would have been relegated to my (crappy) drill press.... I have an ex-RCAF WW2 surplus 5/8" Black and Decker "portable" drill (300 rpm fixed) mounted in a cast iron stand that converts it to a drill press.... Needless to say, any time I need any accuracy I use my milling attachment in the lathe to drill holes.... Maybe someday I'll buy a radial drill press for the bench.... What I ended up getting for the 5C Collets is a square and hex block set on eBay.... http://www.ebay.com/itm/5pc-BRAND-NE...:X:RTQ:US:1123 .... I got a set of 15 collets (1/8" - 1" by 1/16ths) from the same seller, the total was about $178 shipped, and they are on the way.... I will be able to mount the blocks on my milling attachment, so at least I can do holes at 60*, 90*, 120* and 180* from each other.... which should cover 95% of the situations.... I have a stop on one end of the milling vice now, and I'm going to put a matching one on the other end for repetitive operations....

Tomorrow the plan is to make the chambering reamers for the .308 and 357 barrels.... I was thinking of making the 60* tapered section part of the reamer, any reason why not?.... The .308 will look like the nose of the above bolt (but with a long chamber, of course.... The .357 will have the 3/8" section, but the 60* taper will be very short and then the (larger diameter) chamber.... Both will be run in so that the larger end of the taper is in the same position relative to the barrel port and breech end of the barrel.... Probably clear as mud....

Bob

[SeanMP]

I initially drilled the .250" counterbore in the .224 barrel with a stub drill.... turned out fine, nicely centered, (I didn't go very deep) but the (118*?) shoulder was too steep and with the tightness of the chamber it was actually shaving the bullet when I pushed it in.... Soooooooo, I changed to using a center drill with a 60* taper, I had one that was 1/4" OD.... I drilled in until the taper stopped about 0.030" from the barrel port, and then polished the .250" section and the taper with 400 grit, paying particular attention to where the taper met the .224 chamber to smooth and round the edge so there was nothing to shave the bullet.... I think you might want to polish the chamber a bit more if your barrel is as tight as mine.... When I push a bullet in, it polishes the driving bands just going through the section aft of the barrel port, let alone in front of it.... It's pretty difficult to load, actually, requiring quite a lot of force to seat the bullet, especially by the time you get the base flush with the front of the barrel port.... My bolt probe is actually leaving a dent in the base of the bullet, that's how tight it is....

Bob

Hmmm That's bloody odd. I actually got the chamber to the point where the bullet would drop in and settle just before it's final position. Spent hours lapping the two barrels to get them to the point shown in the other thread..........I wonder if the port work displaced at bit of metal??
But yes both barrels are gnat's arse tight.



I wouldn't hesitate to incorporate the 60* taper on the reamer. The LW QB's are done this way because of the multiple steps on the factory bolts.

I would say that 99% of everything you would ever want to do can be handled by the square and hex block. Make a sine plate for everything in between.

[rsterne]

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]

Sean: RE polishing the barrel with Bore Brite (red).... I pulled the barrel and did the chamber area until the felt pucks weren't quite so tight in the bore (maybe 20 strokes).... I then assembled the rod full length, added fresh paste, and did 20 strokes full length, not quite out the muzzle, then reloaded it and did 30 more.... I then removed a section of rod, reloaded with paste and did 15 more, took off another section, reloaded and did another 15.... So, the full barrel got 50 strokes, and the breech end about 100.... I still have yet to clean it and reassemble.... Any suggestions RE the method I used?.... How often should I do this?.... I probably shot about 100-150 rounds already (1 bag)....

Bob

[SeanMP]

Sweet looking valves Bob

I bet your lovin that 5C. Don't forget if it took you all day to do two that's double the production.