My Hayabusa PCP - The Experiment Continues

[Doc Sharptail]

That is impressive work. 30* angled exhaust port? I can see the logic in that one, which leads to the question- is there an in-line a/g in your future?

Regards,

Doc Sharptail

[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

[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.

[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]

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

[rsterne]

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)?....

PS, Sean, I think you will probably be OK with 1.00" travel and a 72 gr. hammer, using a QB hammer spring, but you will likely have to run it pretty close to coil bind.... Your hammer energy should be similar, but the momentum less.... If you can get the hammer up to about 100 gr., both numbers should be similar to what I'm getting with 1.2" of travel and no preload....

Bob

[SeanMP]

This is getting exciting....almost there!

That is a HUGE amount of air. You wont have any problems with flow I dont think.

Sorry I came up bust with all the suppliers I use for gauges on the ship. None of them make a 1" gauge.

Thanks for the information. Now that I have a couple of springs in hand that will definitely work (25lb/in and 28lb/in) I can gain some mass back on the hammer. I drilled the pocket to accommodate every spring possibility. And I can get some of the waist area back as well. I should be able to come up to the 100gr ballpark. Of course this is just for the 308 build. In hindsight I should have moved the valve forward a 1/4"

[rsterne]

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

[SeanMP]

WOW.....Okay so firstly I'm sitting here p!$$!ng myself I'm laughing so hard. Glad you and the barrel are okay (good thing I put carbon fiber armor on it eh)

And ....
EUREKA....ya did it!
106 FPE is freekin outstanding! And a damn nice string to boot.
Initial accuracy looks good and I'm sure it will get better once you work that horse. Polish it out between sessions with the red (bore bright) The velocity should come up and group size down.

[SeanMP]

How is the stripper working?

And how loud is it?